designed for a working pressure of 160 lbs. per square inch, with a
margin of safety of 5.
The dimensions are as follows:
Diameter of shell 12 feet 6 inches.
Shell plate 1-1/8 " thick.
Front and back upper plates 31/32 " "
Back rivet plates 7/8 " "
Back lower plates 7/8 " "
Front tube plate 15/16 " "
Front lower plate 13/16 " "
Furnaces 17/32 " "
Inner tube plate 3/4 " "
Combustion chamber back 17/32 " "
Combustion chamber sides 17/32 " "
Outer sides of wing combustion chambers 9/16 " "
And bottom of centre one to be 9/16 " "
Shell of receiver 7/16 " "
Beds of receiver 5/8 " "
Receiver connecting pipe 3/4 " "
The riveted joints have all holes drilled. The longitudinal seams are
made with butt joints treble riveted, and with double butt straps.
The circumferential seams are lapped and treble riveted.
Fig. 3412 represents the "Martin" boiler for marine engines. In the
return flue there are a number of vertical water tubes which are very
effective in promoting circulation as well as in generating steam. These
boilers are used largely in the United States navy for moderate
pressures.
The following upon the testing and examining of a boiler of this class
is from _Modern Steam Boilers_:
"Every new boiler should, when complete, be tested by water pressure to
double the amount of the intended working pressure; for while the wisdom
of applying as high a pressure as three times the working pressure,
which is sometimes done, may be questionable, experience has shown that
a test by hydraulic pressure will reveal defects that would otherwise be
apt to pass unnoticed.
"For instance, when the top plate of a combustion box is stayed against
the pressure by girder stays that are not stayed to the boiler shell,
the girder stay merely acts to stiffen the top plate, and as a result
the whole pressure on the area of the top plate falls on the walls of
the combustion box. The back tube plate therefore springs down and
transfers part of this pressure to the furnace, causing it to become
elliptical, as may generally be found by the application of rod gauges
fitted to it before testing and tried while the pressure is on.
[Illustration: Fig. 3411.]
[Illustration: Fig. 3412.]
"This flattening under test naturally drew attention to the
defectiveness of girder stays. Another instance may be given with
reference to gusset stays, which, if fitted so as to support too large
an area of back plate, in proportion to the area of combustion box it
supports, may cause the combustion box to distort from its natural
shape, pulling the tube sheet back and flattening the furnace. The
amount of distortion may be only 1/16 inch in some cases, but that is
sufficient to show the existence of unequal strains which require
attention in boiler designing.
"This brings us to the important fact that in almost every instance
where the furnaces of marine boilers collapse, they come down at the
sides, notwithstanding that when collapse occurs from overheating, the
crown of the furnace must have been left bare of water first, and
should therefore come down first, flattening the furnace at the top.
This points to the conclusion, that the top of the furnace received some
extraneous support.
"When a furnace collapses from corrosion, it naturally gives way at the
most corroded part. An hydraulic test to twice the working pressures is
recommended for new boilers only, unless it be small vertical
cylindrical and steam launch boilers, which may always be subjected to
the same test as new main boilers.
"In the case of old main boilers, however, and particularly rectangular
ones, an hydraulic test of less than twice the working pressure may be
employed, the amount being governed by the circumstances of the case.
If, for instance, a boiler has undergone a thorough repair and received
new furnaces, then every part of the boiler should have received
proportionate consideration and an hydraulic test depending upon the
judgment of the responsible engineer, but not less than one and one-half
times the working pressure should be made, while one of one and
three-quarter times could scarcely be objected to. This, however, is a
subject upon which there is some controversy, especially in the case of
old boilers having a good foundation of strength, but patched or local
weak spots, such as combustion chamber backs and sides, these patches
having been, perhaps, made with a view to a more extensive repair in the
near future.
"In such a case as this an hydraulic test sufficient to prove the
tightness of the seams and joints may, perhaps, be all that is
absolutely essential.
"After a boiler has been tested by hydraulic pressure it should be
examined internally, as it sometimes occurs that a stay may break under
the test (especially if gusset stays are employed), and the extra strain
thrown on the adjacent parts may cause them to fail, and thus cause the
destruction of the boiler when under strain.
"When an examination is to be made inside and outside of a boiler, the
boiler must be properly prepared for the same, which may be done as
follows:
"The tubes should be swept; the furnace cleaned out; the fire bars
should be taken out; the bridges in the furnace should be taken down;
the up take smoke box and combustion box should be cleaned out and
swept; every man hole and hand hole or peep hole door should be removed;
the bottom of the boiler should be cleaned out and dried (in damp
weather a little heat may be necessary for this purpose); all
impediments, if any, should be removed in order to allow the bottom
outside to be inspected; at the time of inspection a few mats, good
lights, a hand hammer and small chipping hammer should be at hand. In
the case of a boiler having any plates weakened by corrosion, a 5/8 inch
tapping drill with a drilling brace should also be provided to test the
thickness of such plates if considered necessary.
"The safety valves should invariably be taken out for examination, and
it is a commendable feature sometimes followed to take out the feed
valves, stop valves, blow off and brine cocks; at the same time, all the
deposits that would prevent a thorough examination of the boiler should
be removed. In some cases, however, there may not be time for the
scaling before it is necessary for the repairs to be gone on with, and,
in that case, a good examination may with care be made by an experienced
man.
"To proceed, then, with the examination, the boiler should be entered
through the man hole door beneath the furnaces, examining the boiler
bottom and the bottom and sides of the furnaces all the way along, and
on arriving at the end of the boiler the water space and stays at the
backs of the combustion boxes can be examined as well as the midship
combustion box stays and plates. In an old and corroded boiler it may be
found necessary to use a chipping hammer very freely about the furnaces,
particularly below the lap of the furnace.
"The most corroded part of a furnace will generally be found about on a
line with the fire bars, but the furnaces may have suffered from some
other cause than the corrosion due to ordinary wear, as, for example,
from chemical or galvanic action, and in that case they may be found
comparatively good at the sides but with the extreme bottoms in a
_dangerously_ corroded state, perhaps in the form of pit holes extending
half through the plate and _hidden by a coating of red scale, which
requires to be chipped away before the pit holes are brought to light_.
"Corrosion by galvanic action may have produced honey combing or a
general attack over the surfaces, which have a dark or _dark and
sparkling appearance_, the latter more particularly when corrosive
action has been very active.
"Of these various classes of corrosion that which is the most deceiving
is that which attacks the plates over the largest surface of the plate,
leaving at the same time an apparently smooth exterior surface, for in
this case the extent of the waste cannot be so clearly detected by the
eye, and the only reliable way of testing the thickness is by drilling a
hole through the plate.
"The flanges of the furnaces should always be examined in the bends, for
flaws, for such defects, although not very common, do at times
unexpectedly make their appearance, and might, if not detected, be the
means of breaking the boiler down at sea. This part of the inspection
being made, any drilling that is to be done to ascertain the thickness
of suspected plates may be proceeded with before the rest of the
inspection is made.
"It may, however, be well to remark that a very common defect is the
wasting away of the combustion box plates around the necks of the stays
or the internal surface of the plates, and it is a usual thing for
deposits to accumulate around these necks, hence, unless these deposits
have been removed (particularly in the case of boilers about three years
old), the true condition of the boiler may not be known.
"The plate around the man hole door should next be examined, a great
defect from waste at the surface that makes the water tight joint. Next
comes the man hole door itself, which should have the rubber or other
material used to make the joint cleaned off, for cases have occurred
where the surface beneath was found apparently sound, whereas the
application of a chisel showed that the iron was so corroded that but
little iron was left in the flange, causing great surprise that the
whole door had not blown out. This defect may generally be looked for in
old boilers, and serves to emphasize the necessity for strong wrought
iron doors.
"The outside surfaces of the end plate in the vicinity of the furnace
fronts are a great source of trouble in some boilers, particularly where
plane furnaces are fitted and flush rivets used for connecting them to
the end shell plates.
"The insides of the furnaces and combustion boxes next require
attention. The most common defects here are lamination of the furnace
plate (if of iron), slight collapsing of furnaces, wasting of the
furnace plates (particularly when anthracite coal has been used), and
wasting when the fire bar bearers or bridges have rested against the
plate.
"In the combustion box the buckling of flat plates may have occurred;
plates may have wasted from leaks, distortion of the crown sheet from
shortness of water may have occurred, or tubes may leak, and whenever,
after sounding with the hammer, doubt exists as to the strength of the
plate, a hole should be drilled through to test the thickness.
"The wing sides of the furnace may next be examined (through the usual
peep holes or by having a boiler mounting taken off for the purpose),
and the shell plating on the sides of the boiler, paying special
attention to the plates where the feed water enters.
"We may next examine the outside of the bottom of the boiler, which
should never be totally inaccessible to the eye, and should always be
capable of being reached by a long-handled paint brush, for if kept well
painted, the bottom of the boiler is, so far as the exterior is
concerned, as durable as the other parts of the shell.
"If, however, the bottom is not kept painted and gets damp, and more
particularly from bilge water, it will corrode rapidly, and the boiler
must be lifted for examination. Under these circumstances a new boiler
_must_ at five years, at the very most, be lifted for examination, and
if found comparatively good it should not be taken as an indication of
the probable condition of any other boiler working under similar
conditions, for the only means of avoiding a great risk in this matter
is to rigidly inspect.
"In the case of flat bottomed boilers in small vessels a good result has
obtained by placing them on a bed of cement, which if properly done
excludes the bilge water from approaching the plate; but even this
precaution would scarcely be sufficient to justify an engineer in
neglecting to lift the boiler at reasonable periods for examination of
the bottom.
"The internal examination of the boiler is continued from the top by
examining the stays in the steam space, the tube and tube plates,
getting down between the nests of tubes and reaching the crowns of the
furnaces. The surface of the shell plates should also be examined, more
particularly if the boiler contains plates subject to heat on the
outside and steam on the other (as in the case of wet up take boilers),
for under these conditions a steel plate may become as weak and
unreliable as a piece of cast iron.
"If the boiler is fitted with the superheater, the examination of the
latter is of the utmost importance, as rapid destruction is here a
common occurrence. In the case of a circular marine boiler of any size,
nothing need be taken for granted, even though an hydraulic test be made
up to twice the working pressure, because there is room for a thorough
internal inspection which may disclose defects that would not be shown
from the hydraulic test. The proper proportions of fire grate surface,
heating surface, steam space, etc., in a marine boiler differ with the
type of boiler and engine, and the steam pressure and degree of
expansion employed.
"Upon the question of steam space, for example, it is asserted by many
that marine boilers are not so liable to prime under the higher
pressures, and as a result of this asserted fact the steam receiver is
in some cases being dispensed with.
"It may be observed, however, that priming to any extent is so costly
and detrimental that much consideration needs to be exercised before
dispensing with the provisions ordinarily made to prevent it.
"For circular tubular boilers, having a working pressure of from 60 to
80 lbs. per square inch and to be used for compound engines, the
following proportions represent current practice.
"1st. One square foot of fire grate area to every indicated horse power
of the engine.
"2d. 28 square feet of heating surface[73] to 1 square foot of fire
grate area.
[73] The heating surface here referred to includes the total interior
surface of the tubes, the sides, backs, crowns and tube plates of the
combustion boxes, and that part of the furnace that is above the level
of the fire bars, but does not include the front tube plate (_i. e._,
the tube plate in the smoke box).
"3d. 6-1/2 to 8 cubic feet of steam space to each square foot of fire
grate area.
"4th. 8 to 10 square feet of tube surface to the total heating surface
in single ended boilers.
"5th. 8-1/2 to 10 is about the ratio of tube surface to the total
heating surface in double ended boilers.
"6th. The diameters of boiler tubes should be about one-half inch for
each foot of length of tube. If less, the tube is liable to choke. About
14 cubic feet of steam (of from 60 to 80 lbs. pressure) should be made
for each square foot of fire grate area.
"Each square foot of fire grate will burn from 13 to 18 lbs. of steam
coal per hour. About 1-1/2 cubic feet of live steam (of the above
pressure) is required for each indicated horse power."
CHAPTER XLIV.--HARDENING AND TEMPERING.
Hardening and tempering processes are performed upon steel for three
purposes:
1st. To enable it to resist abrasion and wear.
2nd. To increase its elasticity.
3rd. To enable it to cut hard substances and increase the durability of
the cutting edge.
Of these, the first is the simplest, because the precise degree of
hardness imparted is not of vital importance.
The second is more difficult, because the quality of the steel employed
for such purposes is variable, and hence the tempering process must be
varied to suit the steel. The third is of the greatest importance,
because the articles to be tempered are the most expensive to make, the
duty obtained is of the greatest consequence to manufacturing pursuits,
and the fine grade of steel employed renders it more liable to crack in
the hardening process.
In those mechanical parts of machines which are hardened to resist
abrasion and wear, the quality or grade of the steel is very often
selected with a view to obtain strength in the parts and ease of
mechanical manipulation in cutting them to the required shape, rather
than to the capacity of the steel to harden. Hence, tougher and more
fibrous grades of soft steel termed "Machine" steel, are employed,
meaning that the steel is especially suitable for the working parts of
machines. This class of steel is of a lower grade than that known as
"tool" steel. It is softer, works, both on the anvil and in the lathe,
more easily, and will bear heating to a higher temperature without
deteriorating. It approaches more nearly to wrought iron, and is
sometimes made of so low a grade as to be scarcely distinguishable
therefrom.
The kinds of steel used where elasticity is desired are known as spring
steel, blister steel, and shear or double-shear steel, although, for
small springs, steel of the tool-steel class is often employed.
The word _temper_, as used by the manufacturer of steel, means the
percentage of carbon it contains, the following being the most useful
tempers of cast steel.
_Razor Temper_ (1-1/2 per cent. carbon).--This steel is so easily burnt
by being overheated that it can only be placed in the hands of a very
skilful workman. When properly treated it will do twice the work of
ordinary tool steel for turning chilled rolls, &c.
_Saw-file Temper_ (1-3/8 per cent. carbon).--This steel requires careful
treatment, and although it will stand more fire than the preceding
temper should not be heated above a cherry red.
_Tool Temper_ (1-1/4 per cent. carbon).--The most useful temper for
turning tools, drills, and planing-machine tools in the hands of
ordinary workmen. It is possible to weld cast steel of this temper, but
not without care and skill.
_Spindle Temper_ (1-1/8 per cent. carbon).--A very useful temper for
mill picks, circular cutters, very large turning tools, taps, screwing
dies, &c. This temper requires considerable care in welding.
_Chisel Temper_ (1 per cent. carbon).--An extremely useful temper,
combining, as it does, great toughness in the unhardened state, with the
capacity of hardening at a low heat. It may also be welded without much
difficulty. It is, consequently, well adapted for tools, where the
unhardened part is required to stand the blow of a hammer without
snipping, and where a hard cutting edge is required, such as cold
chisels, hot salts, &c.
_Set Temper_ (7/8 per cent. carbon).--This temper is adapted for tools
where the chief punishment is on the unhardened part, such as cold sets,
which have to stand the blows of a very heavy hammer.
_Die Temper_ (3/4 per cent. carbon).--The most suitable temper for tools
where the surface only is required to be hard, and where the capacity to
withstand great pressure is of importance, such as stamping or pressing
dies, boiler cups, &c. Both the last two tempers may be easily welded by
a mechanic accustomed to weld cast steel.
The preference of an expert temperer for a particular brand of steel is,
by no means, to be taken as proof of the superiority of that steel for
the specific purpose. It may be that, under his conditions of
manipulation, it is the best, but it may also be that, under a slight
variation of treatment, other brands would be equal or even superior. It
may be accepted as a rule that the reputation of a steel for a
particular purpose is a sufficient guarantee of its adaptability to that
purpose, and all that is necessary to a practical man is to be guided by
the reputation of the brand of steel, and only change when he finds
defects in the results, or ascertains that others are using a different
steel with superior results.
Where large quantities of steel are used the steel manufacturers in many
cases request customers to state for what particular purposes the steel
is required, their experience teaching them what special grade of their
make of steel is most suitable.
To harden steel it is heated to what is termed a "cherry red" and then
dipped into water and held there until its temperature is reduced to
that of the water.
_Tempering_ steel as the blacksmith practises it consists in modifying,
lowering, or tempering the degree of hardness obtained by hardening. The
hardening of steel makes it brittle and weak in proportion as it is
hardened, but this brittleness and weakness are removed and the steel
recovers the strength and toughness due to its soft state in proportion
as it is lowered or tempered.
When therefore a tool requires more strength than it possesses when
hardened, it is strengthened by tempering it. Tempering proceeds in
precise proportion as the temperature of the hardened steel is raised.
When the steel is heated to redness the effects of the hardening are
entirely removed, and the steel, if allowed to cool slowly, is softened
or annealed. To distinguish maximum hardness from any lesser degree the
terms to give the steel "all the water," or to harden it "right out" are
employed, both signifying that the steel was heated to at least a clear
red, was cooled off in the water before being removed from the same, and
was not subsequently tempered or modified in its hardness. If a piece of
steel has its surface bright and is slowly heated, that surface will
assume various colors, beginning with a pale straw color (which begins
when the steel is heated to about 430°) and proceeds as in the following
table:--
Fahr.
Very pale yellow 430°
Straw yellow 460
Brown yellow 500
Light purple 530
Dark purple 550
Clear blue 570
Pale blue 610
Blue tinged with green 630
It happens that between the degree of hardness of hardened steel and the
temper due to reheating it up to about 600° Fahr. lie all the degrees of
hardness which experience has taught us are necessary for all
steel-cutting tools. Hence we may use the appearance of colors as
equivalent to a thermometer, and this is called color-tempering. The
presence of these colors or of any one of the tints of color, however,
is no guarantee that the steel has been tempered or possesses any degree
of hardness above the normal condition, because they appear upon steel
that is soft or has not been hardened. To obtain exact results by color
tempering, therefore, the steel must first be thoroughly hardened, and
this is known in practice by the whiteness of the hardened surface.
Any number of pieces hardened so as to have a white surface may be
tempered to an equal degree of color, or heated to an equal
thermometrical temperature, with the assurance that they will possess a
degree of hardness sufficiently uniform for all practical purposes; but
if their hardened surfaces have dark patches, tempering to an equal tint
of color is no guide as to their degree of temper. Successful tempering,
therefore, must be preceded by proper hardening.
The muffle should therefore bear such a proportion in size that when
heated to a blood red, and taken from the fire, its temperature will be
reduced to nearly that of the steel when it has acquired its proper
degree of temper.
The shape of the bore of the muffle should always conform to that of the
article tempered; for round work, a round muffle; for square work, a
square one; and so on. The muffle should be shorter than the work, so
that the tempering of either end of the work may be retarded, if it is
proceeding too fast, by allowing that end to protrude through the
muffle.
Color tempering, it will be observed, gives us no guide or idea of any
of the degrees of temper which occur while the hardened steel is being
heated up to about 430° Fahr.; and thus it leaves us in the dark as to
all the ranges of hardness existing in steel thoroughly hardened and
tempered to any degree less than that due to about 430° degrees of
reheating. How wide this range may be can be appreciated when it is
remembered that in the color test there are only 200° of heat between
the hardness known as straw color, which is hard enough for almost all
cutting purposes, and blue, tinged with green, which is almost normal
softness.
It is for this reason (among others) that where very exact results are
to be obtained and a large number of pieces are to be tempered, fluxes,
heated to the required temperature, are very often employed.
Color tempering is conducted in different ways. In a muffle, in heated
sand, with hot pieces of flat iron, and in boxes heated to the requisite
temperature in an oven, the temperature being indicated by a pyrometer
or heat-gauge. The articles to be tempered remain in the oven a length
of time determined by experiment or experience, these being influenced
by the size and substance, or thickness, of the pieces.
A muffle is a tube or cylinder receiving its heat from the outside and
open at the end or ends to receive the steel. Where tempering is carried
on continuously the muffle is kept in the fire, although it is claimed
by many that better results are obtained by removing it from the fire
when heated. It is obvious that if the muffle is heated evenly the steel
will temper most evenly by being held in the centre of the muffle, or
the piece may be revolved and moved endways in the muffle in order that
the steel may heat evenly. The tempering should always proceed slowly,
otherwise the heat may not have time to penetrate the steel to the
centre, the outside tempering more quickly, thus the tool will be weak
because of the undue hardness of the interior metal. Furthermore,
protruding edges, or slight sections of the steel, may reduce to the
required temper before the main body of the steel, which induces either
serious weakness of the insufficiently tempered part, or softness in the
thin sections, providing that the steel is kept long enough in the
muffle to temper the main body to the proper degree.
In heating steel to harden it, especial care is necessary, particularly
when the tool is one finished to size, if its form is slight or
irregular, or if it is a very long one, because unless the conditions
both of heating and cooling be such that the temperature is raised and
lowered uniformly throughout the mass, a change of form known as
_warping_ will ensue. If one part gets hotter than another it expands
more, and the form of the steel undergoes the change necessary to
accommodate this local expansion, and this alteration of shape becomes
permanent. In work finished and fitted this is of very great
consideration, and, in the case of tools, it often assumes sufficient
importance to entirely destroy their value. If, then, an article has a
thin side, it requires to be so manipulated in the fire that such side
shall not become heated in advance of the rest of the body of the metal,
or it will become locally distorted or warped, because, though there may
exist but little difference in the temperature of the various parts, the
more solid parts are too strong to give way to permit the expansion:
hence the latter is accommodated at the expense of the form of the
weakest part of the article.
Pieces, such as long taps, are very apt to warp both in the fire and in
the water. In heating, they should rest upon an even bed of coked coal,
and be revolved almost continuously while moved endways in the fire; or
when the length is excessive, they may be rested in a heated tube, so
that they may not bend of their own weight. So, likewise, spirals may be
heated upon cylindrical pieces of iron or tubes to prevent their own
weight from bending or disarranging the coils.
Experiments have demonstrated that the greater part of the hardness of
steel depends upon the quickness with which its temperature is reduced
from about 500° to a few degrees below 500°, and metal heated to 500°
must be surrounded by a temperature which renders the existence of water
under atmospheric pressure impossible; hence, so long as this
temperature exists the steel cannot be in contact with the water, or, in
other words, the heat from the steel vaporizes the immediately
surrounding water. The vapour thus formed penetrates the surrounding
water and is condensed, and from this action there is surrounding the
steel a film of vapour separating the water from the steel, which
continues so long as the heat from the steel is sufficiently great to
maintain the film against the pressure of the water and the power of the
water which rushes toward the steel to fill the spaces left vacant by
the condensation of the vapour as it meets a cooler temperature and
condenses. The thickness of the vapour film depends mainly upon the
temperature of the steel; but here another consideration claims
attention. As the heated steel enters the water the underneath side is
constantly meeting water at its normal temperature, while the upper side
is surrounded by water that the steel has passed by, and, to a certain
extent, raised the temperature of. Hence, the vapour on the underneath
side is the thinnest, because it is attacked with colder water and with
greater force, because of the motion of the steel in dipping. For these
reasons it is desirable, especially with thick pieces of steel, to
inject the water in a full stream upon the article, as is done in the
Brown & Sharpe hardening tanks.
In cases where a great many pieces are to be hardened and tempered to an
even degree, the steel is heated for the hardening in a flue with the
advantage that contact between the heated steel and the impurities (as
sulphur or silicon) of ordinary fuels is avoided, and also that all the
pieces may be heated, and therefore hardened, to a uniform degree. The
capacity of this system is great, because a number of pieces can be
heated without fear of any of them becoming overheated if not attended
to immediately. Thus the Waltham Watch Co. heat their mainsprings for
the hardening in a flux composed of melted salt and cyanide of potash,
the latter serving to clean the surface of the steel; but as the latter
wastes it requires to be added occasionally.
The Watch Company, however, find this mixture will not do for the hair
springs, as it alters (to a very small degree, however) the nature of
the steel; hence these springs are heated for hardening in melted glass.
The Pratt and Whitney Co. heat their taps, &c., for hardening in a
composition of equal quantities of salt and cyanide of potash, adding
the latter as it wastes, and temper them by the cold test.
The Morse Twist Drill Co. use a similar compound for heating to harden,
and the following apparatus for dipping. In a large tank having a free
water circulation, stand two pots of a capacity of about five gallons
each, one of these contains cyanide of potash and salt, and another
sperm oil. The heated work is dipped for an instant into the pot
containing the potash and salt, which clean the surface of the steel,
and then cooled in the main water tank; but if the work is, from its
shape, liable to crack, it is at the final cooling dipped in the pot of
sperm oil instead of in the water.
Before heating the steel it is dipped in soft soap to prevent oxidation,
and on dipping it into the potash and salt pot it causes a cracking
sound, the operator knowing from the sound if the mixture is proper, and
how long to hold the steel therein.
This company first fill the heating pot with salt, and then add cyanide
of potash until a trial of the tool gives quite satisfactory results,
adding cyanide of potash as the work proceeds to make up for the
evaporation and keep the mixture of the compound correct.
In many cases it is considered an advantage to harden the outside of an
article, keeping the inside as soft as possible so as to increase the
strength. In such case the article may be heated in red-hot lead, the
surface of which may be covered with charcoal. Under these conditions
the outside of the article, especially if thick, will get red hot in
advance of the inside.
Articles having thick and thin sections may be heated in fluxes to great
advantage, the thick side being immersed first, and the article being
lowered very slowly into the pot of lead. If the shape of the article is
such as to render it liable to crack in the water because of containing
holes or sharp corners in weak parts, these holes and sharp corners may
be filled with fire-clay, the dipping water may be heated to about 50°,
and salt (1 lb. per gallon of water) added to it.
The Monitor Sewing Machine Company harden and temper their spiral
springs at one operation, by heating them to a blood-red heat and
quenching them in a mixture of milk and water, which will give an
excellent result, providing that the springs are heated to precise
uniformity and the mixture of milk and water is correct. For a process
of this kind (which is very expeditious, because the hardening and
tempering is performed at one operation), the steel should be heated to
a very uniform temperature, and a mixture of, say, two-thirds milk and
one-third water tried at first, more milk being added to lower the
temper, or more water to increase it if necessary.
Saws are hardened in compositions of animal oil, such as whale-oil, with
which resin, pitch, and tallow are sometimes mixed.
Resin hardens but somewhat crystallises the metal, but it is used
because, on common saws, the scale will not strike properly without it.
Tallow gives body to the liquid and causes it to extract the heat
quickly from the steel (and the hardening is solely due to the rapid
extraction of the heat). In addition to this, the saws hardened in oil
and tallow show a very fine grain if fractured, and are tough. The
effect of pitch is much the same as that of resin. In place of tallow,
bees-wax is sometimes used, giving an excellent result. A very little
spirits of turpentine mixed with the oil every time it is used (that is,
for every batch) is an excellent ingredient to cause the scale to
strike, but being very inflammable, it is somewhat dangerous. If none of
these ingredients are used, and the scale does not strike, it acts as a
fine separating lining, preventing the contact between the metal and the
liquid, and hence retarding the cooling, and therefore the hardening.
Let us suppose some thin saws of the finest grade of steel are to be
tempered. The liquid would be about half a barrel of tallow to a barrel
of whale-oil (which will harden as hard as glass). After the temperature
of the saw is reduced to that of the bath, it is removed, the adhering
oil is removed, and the surface dried by an application of sawdust, and
the tempering process may be proceeded with.
There are three methods of drawing the temper. One is with the saw lying
in the open furnace; a second, an English plan, is with the saw
stretched in a frame, so as to prevent its warping, and in fact, to
cause the tempering to aid in straightening the saw; and the third is to
temper between flat dies.
In the first, the temper is determined by the appearance of the saw in
the furnace. The saw absorbs some of the liquid in which it was quenched
to harden it; and as it is reheated to temper it, this oil passes off as
a cloud, or rather as a breath passes off the surface of a window-pane.
This action takes place first on the lower surface of the saw, nearest
to the furnace bottom, the oil exuding in a mist-like form. The length
of time the saw must remain in the furnace after the cloud has passed
off is determined by the thickness of the saw and the heat of the
furnace, the operator being guided entirely by experience; but when the
saw is taken from the furnace, it will have a very dark-red glimmer, and
must be laid flat and allowed to cool off in the air, for if again
dipped it would be too hard. When cool, the saw thus tempered will be of
a sky-blue color, and will spring from point to butt without bend or
break. This process requires skilful management and good judgment, but
will give most excellent results. The main objection to it is, that it
is expensive, since it gives no aid to the straightening processes.
The straightening frame, or English tempering system, is as follows: The
plates of steel are made of a size that will cut into four saws. The
furnace front is provided with a tramway extending to the floor of the
furnace, and on this runs the stretcher-frame. The plates are stretched
in the frame, which is run into the furnace so that the plate is heated
under a tension, which operates to straighten them. As the temper
lowers, the screws of the stretcher are turned, increasing the tension;
when the tempering is done, the screws are made to stretch the plates
very tight just previous to taking it from the fire, and the plates are
allowed partly to cool off while kept in the frame. In this process the
indications of the temper are determined as in the first process. In the
third process, the saws are placed between a stationary and a movable
die provided in the body of the furnace, the movable one descending and
pressing the saw to the other die; thus the tempering is accompanied by
a flattening process (the dies being operated by pressure). The degree
of temper is regulated by the temperature to which the saws are heated,
which is ascertained by a pyrometer. The furnace is kept at a constant
temperature, and the length of time the saw remains between the dies is
varied to suit the thickness of the saw. The gain due to this system is,
that less straightening is required and a determinate temperature is
secured. Some makers claim that in this system the vapour of oil that
exudes from the saw has no means of escape, and that a chemical effect
injurious to the steel ensues; and furthermore that the temperature of
the dies will be greatest at or near their circumference, and hence the
teeth and back and the ends of the saw will be softer than the middle of
the width and length of the saw, and that if two saws, one above the
other, be placed on the dies at once, the contacting surfaces of the
saws will be the hardest, and those surfaces will be black by reason of
the oil burning into the steel, instead of exuding, as in the open
furnace process.
The floor of the tempering furnace should be flat and even; for if any
part of the saw-plate lies suspended, it will sag when heated, greatly
increasing the amount of straightening required. The furnace must be so
constructed as to heat evenly all over, otherwise the temper of the saw
will not be even. The air must be carefully excluded to prevent the
steel from decarbonizing, which being thin, it is very apt to do. Thin
saws warp proportionally as they are heated more, and if they are
allowed to remain longer in the furnace and not heated too quickly,
existing buckles or bends will partly straighten themselves in the
furnace. Care must be taken to keep the tongs clear of the teeth, and in
taking the saws from the furnace the length of the saw must stand at a
right angle to the operator (two pairs of tongs being used), so that the
saw's own weight shall not cause it to bend. The saw must be transferred
from the furnace to the bath very quickly, to prevent, as much as
possible, its cooling in the air; for such cooling would take place
unequally, causing the saw to warp, as well as impairing the temper. It
should be dipped with the length horizontal, the teeth downward and the
side faces vertical, and plunged quickly into the bath. On being dipped
in the hardening liquid, they warp again, but the dipping may be
manipulated to partly regulate the warping. From the moment the cold air
strikes the plate a warping process sets in, hence quickness in
transferring from the furnace to the bath is a great point. When the saw
is hot enough to temper, the scale will begin to rise upon its surface,
and if the furnace is unequally heated, the scale will arise first at
the hottest part, instantly notifying the operator of the defect.
From the appearance of the surface of the saw after it comes from the
hardening bath, the operator can see if it is properly hardened. If so,
the scale will be what is termed "struck," that is, it has come off,
leaving the surface from a grey to a white color; while if the scale
remains in dark patches, the saw is too soft in those parts.
After the saws are tempered they are allowed to cool in the open air,
and then require to be straightened by the hammer, and in this process
the tempering has been interfered with, inasmuch as that the elasticity
due to the tempering has been counterbalanced to some extent by the
local condensation of the metal induced by the immediate effects of the
hammer blows. The condensation of the metal has impaired the natural
grain or fibre of the metal, and stiffens it so that if the saw be bent
these stiffened hammer marks will cause it to remain set instead of
springing back straight, as it should do. To remove this defect the saws
are what is termed _stiffened_, that is, they are heated until the
surface assumes a yellow color, when they are removed and allowed to
cool. This causes the metal condensed by the hammer to assume its
natural structural condition, and permits the tempering to spring the
saw back straight, even though it be bent until the two ends touch, and
the bend carried half way along the blade by carrying one end forward
along the blade surface. The yellow color is subsequently removed by an
application of a solution of muriatic acid.
The method employed by the Tomlinson Carriage Spring Company for
carriage springs is as follows:--
The spring plates are heated to bend them to the _former_, which is a
plate serving as a gauge whereby to bend the plate to its proper curve,
which operation is performed quickly enough to leave the steel
sufficiently hot for the hardening; hence the plates after bending are
dipped edgeways and level into a tank of linseed oil which sets in a
tank of circulating water, the latter serving to keep the oil at about a
temperature of 70° when in constant use. About 3 inches from the bottom
of the oil tank is a screw to prevent the plates from falling to the
bottom among the refuse.
To draw the temper the hardened springs are placed in the furnace, which
has the air-blast turned off, and when the scale begins to rise, showing
that the adhering oil is about to take fire, they are turned end for end
in the furnace so as to heat them equally all over. When the oil blazes
and is freely blazed off, the springs are removed and allowed to cool in
the open air, but if the heat of a plate, when dipped in the oil to
harden is rather low, it is cooled, after blazing, in water. The cooling
after blazing thus being employed to equalize any slight difference in
the heat of the spring when hardened.
The furnace is about 10 inches wide and about 4 inches longer than the
longest spring. The grate bars are arranged _across_ the furnace with a
distance of 3/8 inch between them. The coal used is egg anthracite. It
is first placed at the back of the furnace, and raked forward as it
becomes ignited and burns clearly. For shorter springs the coal is kept
banked at the back of the furnace, so that the full length of the
furnace is not operative, which, of course, saves fuel. By feeding the
fire at the back end of the furnace, the gases formed before the coal
burns clearly pass up the chimney without passing over the plates, which
heat over a clear fire.
For commoner brands of steel, what is termed a water-chill temper is
given. This process is not as good as oil-tempering, but serves
excellently for the quality of steel on which it is employed. The
process is as follows: The springs are heated and bent to shape on the
_former_ plate as before said; while at a clear red heat, and still held
firmly to the _former_ plate, water is poured from a dipper passed along
the plate. The dipper is filled four or five times, according to the
heat of the plate, which is cooled down to a low or very deep red. The
cooling process on a plate 1-1/2 × 1/4 inches occupies about 6 seconds
on an average, but longer if the steel was not at a clear red, and less
if of a brighter red, when the cooling began. Some brands of steel of
the _Swede steel_ class will not temper by the water-chill process while
yet other brands will not harden in oil, in which case water is used to
dip the plates in for hardening, the tempering being blazing in oil as
described. In all cases, however, steel that will not harden in oil will
not temper by the water-chill process.
The Columbia Car Spring Company temper their springs as follows:--Using
"Gregory crucible steel," heating is performed in a furnace consuming
gas coke, but the furnace has a number of return enclosed flues, and
between these flues (one over the other), are ovens, the heat passing
through the brick-work forming the flues into the ovens. To facilitate
renewing the ovens (which of course also renews the flues), the floor of
each oven (which forms the ceiling of the oven below), is built on iron
supports, protected by the brick-work and suitable fire clay, the bricks
all being made to pattern, thus involving very little labor in building.
The furnace doors are at the ends, and are kept closed as much as
possible. In this way the steel has no contact with the products of
combustion of the fuel, and the air is excluded as far as practicable
(two valuable features). The furnaces are long and narrow, and not being
connected with the flue there is but little disposition for the cold air
to rush in when the furnace doors are opened.
The hardening and tempering of springs whose coils are of thick
cross-section is performed at one operation as follows: The springs are
heated in the furnace or oven described, and are first immersed for a
certain period in a tank containing fish oil (obtained from the fish
"_Moss Bunker_," and termed "_straights_"), and are then removed and
cooled in a tank of water. The period of immersion in the oil is
governed solely by the operator's judgment, depending upon the thickness
of the cross-section of the spring coil, or, in other words, the
diameter of the round steel of which the spring is made.
The table below gives examples of the hardening and tempering in this
way of springs of the following dimensions:--
Number of coils in spring 5-3/4
Length of the spring 6 inches.
Outside diameter of coils 4-3/4
Diameter of steel 1
+-----------+-----------+-----------+
| | Time of | Number of |
| Examples. | Immersion | Swings in |
| | in Oil. | Oil. |
+-----------+-----------+-----------+
| | Seconds. | |
|First | 28 | 35 |
|Second | 36 | 46 |
|Third | 27 | 36 |
|Fourth | 38 | 40 |
+-----------+-----------+-----------+
As will be seen, the spring in the first example was immersed in the oil
and slowly swung back and forth for 28 seconds, having been given 35
swings during that time. Upon removal from the oil the spring took fire,
was redipped for one second, and then put in the cold water tank to cool
off.
The following are examples in hardening and tempering springs of the
following dimensions:--
Number of coils in the springs 6
Length of the springs 9 inches.
Inside diameter of coils 3-1/4
Size of steel 1 × 1-1/2 square.
+-----------+-----------+-----------+
| | Time of | Number of |
| Examples. | Immersion | Swings in |
| | in Oil. | Oil. |
+-----------+-----------+-----------+
| | Seconds. | |
|First | 9 | 12 |
|Second | 8 | 12 |
|Third | 8 | 12 |
|Fourth | 9 | 12 |
|Fifth | 9 | 12 |
|Sixth | 9 | 12 |
+-----------+-----------+-----------+
To keep the tempering oil cool and at an even temperature, the tank of
fish oil was in a second or outer tank containing water, a circulation
of the latter being maintained by a pump. The swinging of the coils
causes a circulation of the oil, while at the same time it hastens the
cooling of the spring. The water tank was kept cool by a constant stream
and overflow. If a spring, upon being taken from the oil, took fire, it
was again immersed as in the first example. Resin and pitch are
sometimes added to the oil to increase its hardening capacity, if
necessary.
The test to which these springs were subjected was to compress them
until the coils touched each other, measuring the height of the spring
after each test, and continuing the operation until at two consecutive
tests the spring came back to its height before the two respective
compressions. The amount of set under these conditions is found to vary
from 3/8 inch, in comparatively weak, to 7/8 inch for large stiff ones.
The New Haven Clock Company heat their springs in a furnace burning
wood, the springs being _kept in the flames only_, and quenched in a
composition of the following proportions:--"To a barrel of oil 10 quarts
of resin and 12 quarts of tallow are added."
If the springs "fly," that is, break, more tallow is added, but if the
fracture indicates brittleness or granulation of the steel, rather than
excessive hardness, a ball of yellow beeswax, of about 6 inches in
diameter, is added to the above.
These springs are tempered, singly, to a reddish purple by being placed
on a frame having horizontally radiating arms like a "star," which is
attached at the end of a vertical rod. The spring is laid on the "star"
and lowered into a pot of melted lead, being held there a length of time
dictated by the judgment of the operator.
The star-shaped frame is termed a sinker, and if upon being lifted from
the lead the colour of the spring is too high, a second immersion is
given.
APPENDICES
APPENDIX--PART I.
TEST QUESTIONS FOR ENGINEERS.
An efficient engineer must certainly be able to determine any practical
question that may arise in the management, not only of his engine and
boiler, but also in that of such shafting, pulleys, gear wheels, etc.,
as may constitute the driving gear connected with the engine.
A very moderate examination of an engineer (whether to test his
suitability for employment or for promotion) should therefore include
questions tending to determine his capability to give such directions as
may be necessary when the engine or shafting breaks down, or when
alterations are to be made and he is consulted with reference to them.
The following questions have been framed with a view to include such
information as a first-class engineer, and even an assistant or night
engineer, may be expected to possess, and a large proportion of these
questions have been taken from actual engineers' examinations in various
parts of the country.
In many cases engineers of manufactories are required to make, as far as
possible, their own repairs and sometimes indeed also the repairs to the
machinery the engine drives, but to give questions covering this ground
would be to refer the reader to nearly every page in the two volumes,
which is manifestly impracticable.
=Matching gear wheels.=--Suppose you were running a hoisting engine
whose pinion had 15 teeth, driving a wheel with 150 teeth in it; if the
pinion had teeth with radial flanks, what orders would you send to get
another wheel that would work with the pair?--For answer, see Volume I.,
page 15.
=Radial flanks.=--If a pinion has radial flanks what information does
that give to the engineer if at any time he requires to order another
wheel to work with it? I. 15.
=Teeth of gear wheels.=--What is the difference between an epicycloidal
tooth and an involute tooth of a gear wheel? I. 8, 13.
=Ordering bevel gears.=--Two lines of shafting are to be connected by a
pair of bevel gears and one is to run twice as fast as the other; how
would you find the bevel of the wheels so as to be able to tell the
maker what was wanted, and what dimensions would you give, leaving the
pitch and the shape of the teeth out of the question? I. 22.
=Ordering taps.=--Suppose you were ordering a set of taps for use in the
engine room, what precautions would you be obliged to take as to the
shape of the thread in order to get proper taps? I. 85.
=Fitting a nut.=--Will a nut having a United States standard thread fit
a bolt having a common V thread, both threads having the same pitch and
diameter, and how could you tell one bolt from the other? I. 85.
=Curing a pounding cam.=--Suppose some part of the machinery driven by
an engine had a cam motion with a small roller which hammered and
pounded on the cam, how would you cure the defect? I. 83.
=Ordering a new spur wheel.=--Suppose a spur wheel broke and you wanted
to give the diameter for a new one, where would you measure the diameter
of the old one? I. 1.
=Comparing screw threads.=--What is the difference between the common V
thread and the United States standard thread? I. 85.
=Using two set screws.=--When two set screws are placed in a hub how
should they be located? I. 127.
=Best lathe tool.=--What is the most useful turning tool for a hand
lathe, such as is sometimes provided for an engineer to make repairs
with? I. 331.
=Fitting a crank pin.=--How would you proceed to put in by a contraction
fit a crank pin, the crank being on the engine? I. 366.
=Increasing strength of teeth.=--Suppose you had to order a new pair of
wheels to replace a pair whose teeth frequently broke, what alterations
in the dimensions of the wheels would you make so as to get stronger
teeth in wheels of the same diameter? I. 65.
=Wear of a cam roller.=--If an engine had a valve motion worked by a
parallel roller in a parallel cam groove, would the roller wear out
quick, and why? I. 84.
=Altering the speed of a shaft.=--Do a pair of mitre wheels alter the
speeds of the shaft they drive or not? I. 1.
=Driving out a key.=--In driving out a key is a quick or a slow hammer
blow the most effective? II. 65.
=Riveting a crank pin.=--For riveting a crank pin what shape should the
pene or pane of the hammer be? II. 73.
=Face of a cold chisel.=--What is the proper shape for the face of a
cold chisel? II. 73.
=Key bearing.=--What is the effect upon a wheel if its key bears upon
opposite corners? II. 107.
=Fitting a key.=--Should a key be driven lightly or not when fitting it,
and why? II. 106.
=Angle Of wrench jaws.=--What angle should the jaws of a wrench be to
its body in order to enable it to turn a nut in a corner with greatest
advantage? I. 123.
=Chucking a crank.=--How should a crank be chucked in order to prevent
the crank pin from being out of true, and the engine from beating and
pounding? I. 247.
=Chucking a cross-head.=--How should a cross-head be chucked so as to
have its piston rod and wrist pin at a true right angle? I. 252.
=Length of drill edges.=--Why should both edges of a drill be exactly
equal in length and of equal angle? I. 277.
=Boring bar edges.=--Should a boring bar for an engine cylinder have
one, two, three or four cutters? I. 289.
=Spiral spring.=--Give a method of making a spiral spring. I. 329.
=Expansion fit.=--What is meant by an expansion or a contraction fit,
say for an engine crank pin? I. 366.
=Fitting brasses.=--Suppose the joint faces of a pair of brasses are not
square with the sides of the box or strap in which the brasses fit, what
will the effect be when the brasses are locked tight together by the
key? II. 125.
=Wear of brasses.=--When an engineer is taking up the wear of connecting
rod brasses, what must he do to keep the rod of the proper length? II.
124-127.
=Case hardening.=--Describe the simplest method of case hardening. II.
128.
=Fitting pillar block brasses.=--State the proper order of procedure in
fitting in a new pair of main bearing or pillar block brasses for an
engine. II. 130.
=Driving brasses.=--What will be the effect of driving a brass in and
out with a hammer and without a block of wood to strike on? II. 72 and
132.
=Originating a true plane.=--How is a true plane or flat surface
originated? II. 133.
=Cover joint.=--What is the best form of joint for an engine cylinder
cover? II. 137.
=Grinding a cover.=--How must a cylinder cover be moved when grinding
it? II. 137.
=Appearance Of a joint.=--What is the appearance of a finished ground
joint? II. 137.
=Grade of emery.=--About what grade of emery would you use to make a
ground joint? II. 137.
=Best heat joint.=--What is the best kind of joint to withstand great
heat or flame? II. 138.
=Best water joint.=--What are the best kinds of joints for withstanding
water pressure? II. 138.
=Fitting a flange.=--In fitting a flange to a boiler what part of the
flange face should bed most? II. 140.
=Rust joint.=--How are rust joints made? II. 140.
=Leaky plug.=--How would you test the fit of a leaky plug in a cock? II.
144.
=Well-ground plug.=--What is the appearance of a well-ground plug? II.
145.
=Quick brass fitting.=--Describe the quickest method of fitting a new
brass or bearing box to its journal. II. 147.
=Babbitt bearing.=--What is the principal advantage of a Babbitted
bearing? II. 156.
=Adjusting guide bars.=--What two essential points are there in
adjusting the bottom guide bars of an engine? II. 162.
=Setting guide bars.=--Describe roughly the method employed to set guide
bars by means of a stretched line or cord? II. 163.
=Pounding journals.=--What are the two principal causes of the beating
or pounding of the journals of an engine? II. 164.
=Locating a pound.=--How may the location of a pound be discovered? II.
164.
=Cause of pounding.=--What is the ordinary cause of beating and pounding
in an engine? II. 164.
=Wearing down.=--What is the defect induced by letting the parts of an
engine wear down to a bearing? II. 166.
=Testing alignment.=--What are the tests that should be made to find out
what part of an engine is out of line? II. 166.
=Best test for alignment.=--What part of an engine can be used to form
the best test of alignment to cure pounding? II. 167.
=Connecting rod alignment.=--State in a general way the method of using
the connecting rod to place the engine in line, and thus prevent beating
and pounding. II. 167 to 172.
=Difficult alignment.=--What error in the alignment of the parts of an
engine is the most difficult to discover? II. 170.
=Alignment of crank pin.=--What is the general cause of a crank pin
being out of line with the crank shaft? II. 170.
=Pound at quarter stroke.=--When a pound occurs in an engine at the time
the crank pin is at quarter stroke, or thereabouts, where would you look
for the cause? II. 170 to 172.
=Setting a slide valve.=--What are the three objects, either of which a
slide valve may be so set as to accomplish? II. 173.
=Essentials of slide valve setting.=--What are the two operations
essential to the setting of a slide valve? II. 173.
=Squaring a valve.=--Why is the common process of squaring the valve an
improper proceeding? II. 173, 394.
=Crank pin on dead centre.=--How would you proceed to put an engine
crank pin exactly on the dead centre for setting the valve? II. 173,
394.
=Direction of movement.=--What are the considerations that determine in
which direction the engine should be moved when setting the valve? II.
173, 174, 394.
=Setting eccentrics.=--What tools are used to set eccentrics upon shafts
before the shafts are upon the engine? II. 175.
=Patching a break.=--In patching a broken beam or frame, how may the
bolts be made to serve to act as keys closing the crack? II. 178.
=Erecting shafting.=--Give a general or rough description of the method
of adjusting or aligning or erecting shafting. II. 184 to 186.
=Kinds of shafting.=--What is the difference between bright and black
shafting? II. 187.
=Fitting a pulley.=--If you had a pulley whose bore was 1-15/16 inches,
what diameter of bright shafting would you order for it? II. 187.
=Locating collars.=--What is the best location for the collars that
prevent end motion on a line shaft? II. 189.
=Ball and socket hangers.=--What are the advantages of hangers having a
ball and socket adjustment? II. 192.
=Shaft couplings.=--What four objects should the couplings for line
shafts accomplish? II. 194.
=Universal joint.=--What object does a universal joint accomplish? II.
199.
=Crowning a pulley.=--What is the object of crowning a pulley? II. 201.
=Pulley balance.=--Why should a pulley be balanced? What is a running
and what a standing balance for a pulley? At what speed should a running
balance be made? II. 202.
=Size of pulleys.=--If a shaft makes 150 revolutions per minute, and it
is required to drive a pulley on a machine at 600 revolutions, what
proportions must the diameter of the two pulleys have, and what
determines the diameters of the pulleys? II. 205, 206.
=Testing belts.=--What appearance in leather belting indicates that it
was cut from the spongy shoulder? II. 208.
=Stronger side of belts.=--Which is the stronger side of leather, the
smooth or grain side or the rough or flesh side? II. 208.
=Placing a belt tightener.=--Should a belt tightener be placed on the
tight or slack side of a belt? II. 210.
=Crossed vs. open belt.=--Which will transmit more power, an open or a
crossed belt, and why? II. 210.
=Crossed belt.=--What are the objections to a crossed belt? II. 210.
=Shortening a round belt.=--Can a round twisted belt be shortened
without removing either the hook or the eye and how? II. 216.
=Wide belt.=--How would you get a very wide belt on a pulley? II. 217.
=Mending an eccentric rod.=--Suppose an eccentric rod broke, and you
were required to weld it again, what shape could you make the scarf for
the weld? II. 234.
=Butt weld.=--What is a butt or pump weld? II. 236.
=Scarf weld.=--Describe roughly the means you would employ to make a
scarf weld. II. 235.
=Tongue weld.=--What are the shapes of the two pieces that come together
in a tongue weld? II. 235.
=Strain on boiler joint.=--How would you calculate the amount of stress
there is upon the riveted joint of a boiler? II. 350.
=Shearing strain.=--What is meant by the terms, shearing, tearing and
crushing strains of a steam boiler? II. 351.
=Lapped and butt joints.=--How does a lapped joint differ from a butt
joint or seam in a boiler? II. 352.
=Chain and zigzag riveting.=--How does a chain riveted joint differ from
a zigzag riveted joint? II. 352.
=Butt joint.=--What are the advantages of the butt joint? II. 352-353.
=Margin for holes.=--How would you find the proper distance the rivet
holes should be from the edge of the plate in a boiler seam? II. 353.
=Spacing rows Of rivets.=--How would you find the distance apart for the
rows of rivet holes in a double riveted joint? II. 353.
=High percentage joint.=--What is meant by a "high percentage" riveted
joint? II. 353.
=Single and double shear.=--What is meant by a rivet being in single
shear or double shear? II. 353.
=Allowance for shear.=--How much additional allowance is made in the
shearing strength of a rivet in double shear over that of the same rivet
if in single shear? II. 358.
=Taking charge of a boiler.=--What is the first thing you would do in
taking charge of a boiler? II. 368, 400.
=First inspection.=--What part of the boiler would you inspect first?
II. 368.
Safety valve defect.--To what defect is a safety valve most liable? II.
368, 400.
=Water supply.=--How much water should there be in the boiler when the
fire is lit? II. 368.
=Reliability of gauge glass.=--Is a gauge glass always reliable for
showing the height of the water in the boiler? II. 368, 402.
=Testing gauge glass.=--What would you do to find out if the gauge glass
was showing the correct water level? II. 368.
=Condensation in boiler.=--What is likely to happen if the steam
condenses in the boiler without any of the cocks being open? II. 368,
400.
=Cleaning a boiler.=--What parts of the boiler would you clean before
lighting the fire? II. 368.
=Laying a fire.=--How would you lay the fire? II. 368.
=Quick combustion.=--Does bituminous (soft) or anthracite (hard) coal
light more easily? II. 368.
=First coal.=--How soon would you put coal on after the fire is lit? How
deep would you make the first layer of coal? II. 368, 401.
=Amount of coal.=--How much coal would you put on the fire at a time?
II. 368, 401.
=Even heat.=--How can an even temperature be kept up in the fire box?
Why is it necessary to keep an even temperature in the fire box? II.
368, 370.
=Shaking grate.=--What is the advantage possessed by shaking grate bars?
II. 369.
=Before cleaning a fire.=--What preparations would you make before
cleaning the fire? II. 369.
=Fire tools and their uses.=--What tools are used in cleaning a fire?
And what is the use of each? II. 369.
=Draught while firing.=--How should the draught be regulated while the
fire is being cleaned? II. 369.
=Temporary interruption.=--What should be done to prevent blowing off
through the safety valve when the engine is stopped and no steam is
being taken from the boiler? II. 369.
=Blue flame.=--What does blue flame in the fire box indicate? II. 369.
=Water supply at night.=--How much water would you have in a boiler when
leaving it for all night? II. 369.
=Fire at night.=--How would you leave the fire for the night? II. 369.
=Banking.=--What is banking a fire? Give a safe method of banking a
fire. II. 369, 401.
=Dampers at night.=--How should the dampers be left when the fire is
banked? II. 369.
=Safety valve at night.=--How would you set the safety valve for a
banked fire? II. 369.
=Opening a banked fire.=--What is the first thing to do in starting up a
banked fire? II. 369, 401.
=Regulating boiler feed.=--How would you regulate the boiler feed? II.
369.
=Regulating a pump.=--How can a pump be regulated so as to be kept
pumping without surcharging the boiler? II. 369.
=Even boiler injection.=--Can a continuous feed be maintained if
injectors are used? II. 370.
=Stuck valve.=--How may a stuck valve or a check valve be released? II.
370.
=Hot feed water.=--What would you do if the feed water got so hot that
the pump worked imperfectly or not at all? II. 370.
=Scale.=--What causes scale to form in the boiler and what effect does
scale have on the boiler? II. 370.
=Preventing scale.=--What are the principal methods employed to prevent
the formation of scale in the boiler? II. 370.
=Horizontal heater.=--What advantage does a horizontal heater possess?
II. 370.
=Dirty gauge glass.=--What should be done to the gauge glass if the feed
water is dirty? How many times a day should the gauge be blown out? II.
370.
=Priming.=--What is the priming or foaming of the water in a boiler?
What are the known causes of priming? Why is priming wasteful? Can
blowing off at the safety valve cause priming? What are other causes of
priming? How can priming be detected? What would you do to stop priming?
What would you do to prevent priming? What parts of the engine would you
attend to if the boiler primes? II. 370.
=Low water.=--What would you do if the water got dangerously low in the
boiler? In such a case how would you regulate the dampers? What do you
consider dangerously low? What is blowing down a boiler? II. 370.
=Cleaning a boiler.=--How often would you clean a boiler? II. 371.
=Water falling.=--What would you suppose was going wrong if the pump was
kept going and the water still fell in the boiler? II. 370.
=Empty pump.=--What causes a pump to fail? II. 370.
=Blowing down.=--How much would you blow down a boiler? How low should
the pressure get before the water is let out? What would be the result
if the boiler was blown off under a high pressure? What would you do
after the water is all out of the boiler? II. 371.
=Special examination.=--What parts would you pay special attention to in
examining the boiler after cleaning it? II. 371.
=Hammer test.=--What does the "hammer test" consist of? II. 371.
=Washing and scaling.=--What determines the periods at which a boiler
should be washed out and scaled? II. 371.
=Regulating dampers.=--How would you regulate the dampers when letting
the fire out? II. 371.
=Naming the parts.=--Name all the parts of a simple or plain D
slide-valve engine, beginning with the cylinder. II. 372.
=Dividing the parts.=--Into what three divisions may the parts of a
plain slide-valve engine be divided? II. 372.
=Defining clearance.=--What is the meaning of the word "clearance" as
applied to an engine cylinder? II. 372.
=Finding equal clearance.=--How would you proceed to find if the
clearance in the cylinder was equal at each end? II. 372, 404.
=Parts of valve motion.=--What parts constitute the valve motion or
valve gear? II. 372.
=The driving parts.=--What parts constitute the driving or
power-transmitting mechanism? II. 372.
=Lubricating attachments.=--Name the attachments used upon an engine
cylinder to lubricate the piston and valves. II. 373.
=Pet cock.=--What is the difference between a cylinder pet cock and a
cylinder relief valve? II. 373.
=Relief valves.=--What are cylinder relief valves used for? II. 373.
=Quick steam admission.=--Which gives the quickest steam admission, a
long and narrow or a wide and short steam port, both having the same
area? II. 373.
=Placing the piston-ring split.=--At what part of the cylinder bore
should the split of a piston ring be placed? II. 374.
=Fitting a piston ring.=--How tight should a piston ring fit to the
cylinder bore? II. 374.
=Testing steam tightness.=--How would you test the steam tightness of a
piston? II. 374.
=Jacketed.=--What is a jacketed cylinder? II. 374.
=Valve gear.=--What is a releasing valve gear? What is a positive valve
gear? II. 374.
=Packing a stuffing box.=--About how full of packing would you fill a
stuffing box for a piston gland? II. 375.
=Connecting rods.=--What are the two principal kinds of connecting rods?
What is meant by the angularity of a connecting rod? II. 375.
=Oiling guide bars.=--Which guide-bar is the most difficult to oil, the
top or the bottom one? II. 375.
=Effect of angularity.=--What effect does the angularity of the
connecting rod have on the piston motion? Is this effect increased or
diminished by shortening the connecting rod? II. 375.
=Crank at full power.=--When the crank is at its point of full power, is
the piston in the middle of the cylinder? Is it nearer to the crank-end
or the head-end of the cylinder? II. 375.
=Piston motion irregular.=--What causes the piston to have irregular
motion? II. 375.
=Live steam period.=--What constitutes the live steam period of a
position? II. 376.
=Cut-off.=--What is the point of cut-off? II. 375.--What is a separate
cut-off valve, and what event does it control in the supply of the steam
to the cylinder? How is the point of cut-off varied when a cut-off valve
is used? II. 378.
=Working expansively.=--What causes the steam to be worked expansively
in an engine cylinder? II. 402.
=Follower.=--What is a piston follower? II. 374.
=Valve lead.=--What is the lead of valve? II. 376.
=Valve lap.=--What is the lap of a valve? II. 376.
=Admission.=--What is the point of admission? II. 376.
=Cushioning.=--At what point in the valve travel does cushioning begin?
II. 376.
=Release and compression.=--What are the points of release and of
compression? II. 376.
=Double-ported valve.=--What is a double-ported valve? II. 377.
=Valves.=--What is a griddle valve? What is a balanced valve? II.
377.--What is a piston valve? II. 378.
=Slide and piston valves.=--Is there any difference between the action
of a plain slide valve and a piston valve if both have the same amount
of lap, lead, and travel? II. 378.
=Cut-off diagram.=--Make a diagram to give the dimensions of a slide
valve, to cut off at 3/4 stroke, the valve travel being 4 inches. II.
380.
=Reversing an engine.=--What is the ordinary means provided for
reversing an engine? II. 383.
=Full gear.=--What is the meaning of the term full gear, with regard to
a link motion? II. 383.
=Third use Of link motion.=--What does a link motion accomplish besides
enabling the engine to run in either direction? II. 383.
=Slide valve for link motion.=--What are the two operations to be
performed in setting the slide valve of an engine having a link motion?
Describe these two operations. II. 383.
=Governors.=--What is a throttling governor? What is an isochronal
governor? What is a dancing governor? II. 384.
=Forward.=--What is full gear forward? II. 383.
=Backward.=--What is full gear backward? II. 383.
=Starting.=--How would you proceed to start a plain slide valve? II.
384, 400.
=Crank position.=--What is the best position for the crank to be in to
start the engine, and why is it the best position? II. 384.
=Taking charge.=--What is the first thing you would do in taking charge
of an engine? II. 385.
=Length of connecting rod.=--How would you find out if the connecting
rod was the right length to give an equal amount of clearance at each
end of the cylinder? II. 385, 404.
=Order of examination.=--In what order should a thorough examination of
the engine be made? II. 385.
=Least examination.=--What would constitute the least permissible
examination of an engine, with a due regard to safety? II. 385.
=Thorough examination.=--What would constitute a complete examination of
a plain slide-valve engine? In what order should such an examination be
made? II. 385.
=Quick examination.=--What examination should an engineer make of a
plain slide-valve engine, if called upon to start it as quickly as
possible without knowing its condition? II. 385.
=Taking a lead.=--How would you take a lead for adjusting the fit of a
bearing to its journal? II. 386.
=Set of slide valve.=--How would you test whether the slide valve was
set properly? II. 386.
=Squaring a valve.=--Is it proper to square a plain slide valve? II.
386.
=Lead affected by wear.=--How does the wear of the parts affect the lead
in vertical engines? II. 386.
=Heating of crank-shaft.=--What would you do if the crank-shaft bearings
began to heat? II. 386.
=Hot crank-pins.=--What are the principal causes of hot crank-pins? II.
386.
=Heating.=--What part of the engine is the most likely to get hot from
the friction of the fit? II. 386.
=Use of lead.=--What is a lead used for in adjusting the fit of a brass
to its journal? II. 386.
=Fit of top brass.=--When a liner is used between the two brasses, what
does the fit of the top brass depend upon? II. 386.
=Oiling.=--In oiling the engine, what precaution would you take to
prevent the journals from heating? II. 401.
=Cold weather.=--What is liable to happen to an engine that is used out
of doors in cold weather? II. 386.
=Leaky throttle valve.=--What damage might a leaky throttle valve do,
and how would you prevent it? II. 386.
=Leaky check valve.=--What damage may a leaky check valve do, and how
would you prevent it? II. 387.
=Freezing in the pump.=--How would you prevent the water from freezing
in the pump? II. 387.
=Freezing oil.=--How would you prevent the oil from freezing? II. 387.
=Thawing oil.=--How would you thaw frozen oil? II. 387.
=Setting a portable engine.=--How should a portable engine stand when it
is at work, and why should it stand so? II. 387.
=Natural supply of water.=--What precaution would you take when feed
water is drawn from a stream, or other natural source of supply? II.
387.
=Pumps.=--Into what classes may pumps be divided? What is a force pump?
What is a piston pump? What is a single-acting pump? What is a
double-acting pump? II. 387.
="Suction."=--What causes the flow of water up the suction pipe of a
pump? How high can a pump lift water, or cause it to lift or rise? II.
388.
=Regulating a pump.=--How can the quantity of water a pump will deliver
be regulated? II. 388.
=Pump valves.=--What is the check valve of a pump? What is the foot
valve of a pump? II. 388.
=Speed of pumping.=--What is the highest speed at which a pump should
run? What is the consequence if a pump runs too fast? II. 388.
=Locating the air chamber.=--When should the air chamber be placed on a
pump, and what is its use? II. 388.
=Belt pump.=--What is the advantage possessed by a belt pump? II. 388.
=Starting bar.=--What is a starting bar, and what is it used for? II.
389.
=Link sketch.=--Make a rough sketch of a locomotive link motion. II.
392.
=Link gear and eccentric.=--Does a link motion when in full gear operate
the valve much different to what a simple eccentric motion would do? II.
393.
=Exchanging eccentric rods.=--If the forward eccentric rod was to break,
could the backward eccentric be utilized to run the engine forward? If
so, how? II. 393.
=Broken reach rod.=--How would you hold the tumbling shaft if the reach
rod broke? II. 393.
=Eccentric and crank motions.=--Does the acting eccentric lead or follow
the crank when the link is in full gear? II. 393.
=Setting a slide valve.=--In what position would you place the link
motion when the slide valve is to be set? II. 394.
=Length of eccentric rod.=--What determines the length of the eccentric
rods when setting the slide valve? II. 394.
=Setting an Allen valve.=--What difference is there between setting a
common slide valve and another (an Allen) valve? II. 395.
=Injector.=--What is an injector? II. 395.
=Before firing.=--What should be done before laying the fire? II. 400.
=Kindling the fire.=--How long should the wood burn before putting on
coal? II. 400.
=Oiling.=--What points require examination when oiling the engine? II.
401.
=After oiling.=--What points would you move after having oiled the
engine? II. 401.
=Using tallow.=--Where would you place tallow in oiling the engine, and
for what purpose would you use it? II. 401.
=Fire too hot.=--What would you do if steam was rising too rapidly? II.
401.
=Link position.=--Where should the link be when starting the engine? II.
402.
=Even steam pressure.=--Why should the steam pressure be kept up, and
what difference does it make in the consumption of the fuel? II. 402.
=Quick steaming.=--Can steam be made quickest with a large or with a
small quantity of water in the boiler? II. 402.
=Best boiler feed.=--Which is better, a constant or an intermittent
boiler feed? II. 402.
=Best firing.=--Which is better, heavy firing at long intervals or light
and frequent firing, and why? II. 402.
=Broken cylinder cover.=--What would you do if the cylinder cover got
knocked out while on the road? II. 402.
=Hot piston rod.=--What would you do if the piston rod got hot? II. 403.
=Broken piston rod.=--What if the piston rod broke? II. 403.
=Broken crank-pin.=--What if the crank-pin broke? II. 403.
=Tire off.=--What if a wheel tire came off? II. 403.
=Driving wheel off.=--What if a driving wheel came off? II. 403.
=Broken lifting link.=--What if a lifting link or saddle-pin broke? II.
403.
=Slipping eccentric.=--What if an eccentric slipped? II. 403.
=Hot axle-box.=--What if an axle-box got hot? II. 403.
=Broken spring hanger.=--What if a spring or spring hanger broke? II.
403.
=Bursted tube.=--What if a tube bursted? II. 403.
=Fitting axle-box wedges.=--In what position should the engine be placed
when the axle-box wedges are to be adjusted for fit to the pedestals?
II. 404.
=Changing clearance.=--What is it that, as the engine wears, tends to
alter the amount of clearance? II. 404.
=Crank-pin centres.=--How would you get the distance from centre to
centre of the crank-pins when adjusting the axle-boxes and the side
rods, parallel rods, or coupling rods, as they are promiscuously termed?
II. 404.
=Adjusting Shoes.=--In what position would you place the crank when
adjusting the shoes or wedges of the axle-boxes? Why is this adjustment
important? II. 404.
=Force, pressure, and power.=--What is the difference between force or
pressure and power? II. 405.
=Increase of power.=--Can we increase a given amount of power by means
of mechanical appliances? II. 405, 406.
=Speed vs. power.=--Is a gain in speed a loss in power? II. 405.
=Lever.=--Explain the principle of the lever. II. 405.
=Elements of power.=--What are the three elements composing power? II.
407.
=Horse-power.=--What is a horse-power as applied to steam-engine
calculations? How would you calculate the horse-power of a steam engine?
II. 407.--Give a method of testing the effective horse-power of an
engine. II. 408.
=Safety-valve problem.=--A safety valve is three inches in diameter; the
lever is twenty-eight inches long from the point of suspension of the
weight to the pivoted end of the lever; the valve pin is four inches
from the pivot; the weight is twenty pounds. What is the greatest
pressure of steam the valve will hold, leaving the weight of the valve
and of the lever out of the question? II. 409.
=Thermal unit.=--What is the heat unit or thermal unit? II. 410.
=Latent heat.=--Is all the heat in steam or water shown by a
thermometer? What is the latent heat of water? What is the latent heat
of steam? II. 410.
=Sensible heat.=--What is the sensible heat of steam? II. 410.
=Total heat.=--What is the total heat of steam? II. 410.
=Heaviest water.=--At what temperature is water at its greatest density?
What is the weight of a cubic foot of water when at its maximum density?
II. 410.
=Heat of boiling water.=--What determines the temperature at which water
will boil? II. 410.
=Heat of steam.=--Can steam be made hotter than the water while they are
in contact? What is superheated steam? II. 410.
=Absolute pressure.=--What is meant by the absolute pressure of steam?
II. 411, 416.
=Dry steam.=--What is meant by dry steam? II. 411.
=Weight of steam.=--Is there any difference between the weight of water
and that of the steam it will evaporate into? II. 411.
=A perfect gas.=--What is Marriotte's law, or Boyle's law? Is steam a
perfect gas? II. 411.
=Joule's equivalent.=--What is meant by the conversion of heat into
work? What is Joule's equivalent? What is the mechanical equivalent of
heat? II. 411.
=Indicator.=--What is a steam-engine indicator? II. 413.--How are
indicators attached to an engine? II. 416.
=Indicator diagram.=--What are the names of the lines of a diagram? Why
is a theoretical diagram not correct? II. 414.--What difference is there
between the lines of a diagram of a condensing and those of a
non-condensing engine? II. 415.--How is the expansion curve of a diagram
tested? II. 417.
=Barometer.=--What is a barometer, and for what purpose is it used in
connection with engine diagrams? II. 415.
=Horse-power by diagram.=--How do you calculate the horse-power of a
steam engine from an indicator diagram? II. 418.
=Diagram vs. diagram.=--What difference is there between the diagram
taken from one end and that taken from the other? II. 419.
=Consumption of steam by diagram.=--How would you calculate the
consumption of steam or water of an engine from an indicator diagram?
II. 420.
=Steam line.=--What would a fall in the steam line of a diagram
indicate? II. 421.
=Expansion curve.=--If the expansion curve is above the true expansion
curve, what defect in the engine does that indicate? If the expansion
curve falls too low, what does it indicate? II. 421.
=Valve lead by diagram.=--How would insufficient valve lead be shown on
a diagram? II. 421.
=Excessive lead.=--How is excessive lead shown on a diagram? II. 421.
=Automatic cut-off.=--What is an automatic cut-off engine? What are the
principal forms of automatic cut-off engines? II. 423.
=Releasing valve governor.=--What kinds of governors do engines with
releasing valves have? II. 423.
=Corliss engine valves.=--How many valves does a Corliss engine have?
Explain the action of a Corliss valve gear. II. 423.
=Crab claw.=--What duty does the latch-link or crab-claw of a Corliss
valve gear perform? II. 423.
=Valve trip.=--What means are employed in a Corliss engine to trip the
admission valve? II. 423, 424.
=Point of cut-off.=--What determines the point of cut-off in a Corliss
engine, and how does it do so? II. 424.
=Valve closing.=--What closes the valve in a Corliss engine? II. 424.
=Dash-pot.=--What is a dash-pot? What enables the dash-pot of a Corliss
engine to work noiselessly? II. 424.--How is the amount of air cushion
in the Corliss dash-pot regulated? II. 425.
=Shape of Corliss valve.=--What shape is a Corliss valve, and how far
would its lap, as ordinarily constructed, carry the live steam period,
leaving the cut-off mechanism out of the question? II. 426.
=High-speed engines.=--What is meant by the term high-speed engines? II.
427.
=Adjusting for load.=--What adjustments would you make if the engine had
been running a very light load, and required to be adjusted for a heavy
load? II. 427.
=High-speed governor.=--What class of governor is generally used upon
high-speed engines? II. 427.
=Varying the cut-off.=--What is the usual method of varying the point of
cut-off on high-speed engines? II. 427.
=Wheel governor.=--State, in a general way, what a wheel governor
consists of. II. 427.
=Even valve lead.=--Can the valve lead be kept equal when the point of
cut-off is varied by shifting the eccentric across the shaft or
crank-axle? II. 427.
=Marine engine.=--What forms of engine are used for marine purposes? II.
434.
=Inverted cylinder.=--What is an inverted cylinder engine? II. 434.
=Receiver.=--What is a receiver? II. 434, 453.
=Triple expansion.=--What is a triple-expansion engine? II. 436.
=Condensing engine.=--What is a condensing engine? II. 434.
=Compound engine.=--What is a compound engine? II. 434.
=Arranging compound cylinders.=--What are the two methods of arranging
compound cylinders? II. 436.
=Condenser.=--What is a surface condenser? II. 440.
=Hot well.=--What is a hot well? II. 440.
=Steam condensation.=--Describe the means by which the steam is
condensed after it is exhausted from the cylinder in a surface
condensing engine, and state what becomes of the water of condensation
and the injection, circulating, or condensing water. II. 440.
=Condenser tubes.=--How are condenser tubes made tight? II. 440.
=Blow-through valve.=--What is a blow-through valve? II. 440.
=Air pumps.=--What is a bucket air pump, and is it single or double
acting? What is a piston air pump? What is a plunger air pump? What is a
trunk air pump? When is a trunk air pump necessary? II. 441.
=Air-pump valves.=--Are a foot valve and a head valve always necessary
to an air pump? II. 441.
=Pet cock.=--Why are bucket pumps provided with a valve or pet cock? II.
441.
=Bilge injection.=--What is a bilge injection? What fittings are
necessary for a bilge injection? II. 441.
=Hot-well temperature.=--At what temperature is the water in the hot
well usually kept? II. 441.
=Use of air chamber.=--What is an air vessel or air chamber used on a
pump for? II. 441.
=Feed escape.=--What is a feed relief, or feed escape valve? II. 441.
=Checked boiler feed.=--What causes may act to stop the boiler feed? II.
441.
=Admitting the exhaust.=--When the exhaust steam is condensed for
boiler-feeding purposes, how soon after the engine has started would you
let the exhaust into the feed tank? II. 441.
=Ship's side discharge.=--What is a ship's side air pump discharge
valve? II. 442.
=Course of water.=--What is the course of the main injection water of a
jet condenser? What is the course of the main circulating water of a
surface condenser? II. 442.
=Surface condensing.=--What are the advantages of surface condensing?
How are surface condensers cleaned out? II. 442.
=Engine-room cocks and valves.=--What cocks and valves are there in the
engine room of a condensing engine? II. 442.
=Donkey engine.=--What is a donkey engine? What pipes connect to a
donkey engine, and what are their uses? II. 442.
=Pipes to the sea.=--What are the pipes that lead from or go to the sea?
II. 442.
=Parts classified.=--What parts of a marine engine are generally made of
wrought iron, of cast iron, of brass, and what of steel? II. 442.
=Use of Babbitt.=--What is Babbitt metal or white metal used for? II.
442.
=Use of Muntz.=--What is Muntz metal used for? II. 442.
=Breaking strain.=--About what is the breaking strain of wrought iron
per square inch of section? II. 442.
=Tempering.=--How is steel tempered? II. 442, 460-463.
=Case-hardening.=--What is case-hardening? What parts of an engine are
usually case-hardened? II. 442.
=Forging.=--What are the forgeable metals used in engine construction?
II. 442.
=Welding.=--What is welding? II. 442.
=Metal expansion.=--What metals used in engine construction expand by
heat, and what allowances are made in the construction on this account?
II. 442.
=Composition of iron and steel.=--What is the difference in the
composition of cast iron and steel? II. 442.
=Marine piston.=--Describe a marine engine piston. II. 442.
=Drain cocks.=--What are cylinder drain cocks? II. 442.
=Link motion.=--What is a link motion? What is a link motion used for?
II. 443.
=Expansion valve.=--What is a separate expansion valve? II. 443.
=Top cylinders.=--What are the small cylinders on top of the steam
chests used for? II. 443.
=The throw.=--What is the throw of an eccentric? II. 443.
=Double beat.=--What is a double-beat valve? II. 443.
=Expansion joint.=--What is an expansion joint? II. 141, 443.
=Oil cup.=--What is an oil cup? II. 443.
=Siphon.=--What is a siphon or worsted? II. 443.
=Impermeator.=--What is a steam lubricator or impermeator? II. 444.
=Hand-worked valves.=--What are the valves of a marine engine that are
worked by hand? II. 444.
=Vacuum gauge.=--What is a vacuum gauge? What is a mercury vacuum gauge?
II. 444.
=Total condenser pressure.=--How would you find the total pressure in a
condenser? II. 444.
=Racing.=--What is meant by the racing of an engine? II. 444.
=Uniform paddle-wheel revolution.=--How may the speed of revolution of
single crank paddle-wheels be made uniform? II. 444.
=Paddle-wheel construction.=--What is the construction of a common
paddle wheel? What is a radial paddle wheel? What is a feathering paddle
wheel? II. 445.
=Disconnecting engine.=--What is a disconnecting paddle engine? II. 445.
=Propeller thread.=--Where is the thread of a screw propeller measured?
II. 445.
=Propeller pitch.=--What is the pitch of a propeller? II. 445.
=L. H. propeller.=--What is a left-hand propeller? II. 445.
=Thrust bearing.=--What is a thrust bearing? II. 445.
=Propeller fastening.=--How are screw propellers fastened to their
shafts? II. 445.
=Marine engine pipes.=--What are the principal pipes of a marine engine
and boiler? II. 445.
=Mud box.=--What is a mud box? II. 445.
=Course of steam.=--Describe the course of the steam from the boiler to
the hot well. II. 445.
=Exposure to cold.=--What parts of an engine are exposed to danger in a
cold climate? II. 446.
=Preventing freezing.=--What precautions are necessary to prevent the
engine from freezing in cold climates? II. 446.
=Failure to start.=--Name all the reasons that may cause a marine engine
to fail to start when it is expected to do so. II. 446.
=Pressure pieces.=--Name all the pieces of an engine through which the
steam pressure is received and transmitted. II. 446.
=Horse-power.=--What is the unit or measure of horse-power? What is the
meaning of nominal horse-power? II. 446.
=Lost vacuum.=--Name all the causes from which the vacuum may become
defective or lost. II. 447.
=Hot journals.=--What are the principal causes of the heating of engine
journals? II. 447.
=Stays.=--What is a boiler stay? What is a gusset stay? What is a tube
stay or a stay tube? II. 452.
=Stress per square inch.=--How much stress is usually allowed per
sectional square inch of boiler stay? II. 452.
=Breaking of tubes.=--What is the commonest cause of boiler tubes
breaking? II. 452.
=Split tube.=--How is a split tube stopped up? II. 452.
=Uptake.=--What is the uptake of a marine boiler? What is a wet uptake?
II. 453.
=Superheater.=--What is the superheater of a marine boiler? II. 453.
=Fittings.=--What fittings are essential to a marine boiler? II. 453.
=Safety valves.=--What is a dead-weight safety valve? What is a
spring-loaded safety valve? What is a lock-up safety valve? II. 453.
=Test cocks.=--What do the three boiler test cocks show? How are boiler
test cocks cleaned? II. 453.
=Steam gauges.=--What is a gauge glass or water-gauge glass? What is a
Bourdon dial gauge? What pressure is shown by a boiler steam gauge? II.
453.
=Scum cocks.=--How many scum cocks are used in a marine boiler? II. 454.
=Sluice valves.=--What are sluice valves in steamships? II. 454.
=Removing scale.=--How is scale removed in boilers? II. 454.
=Salinometer.=--What is a salinometer? II. 455.
=Salt in sea water.=--About how much salt does sea water contain? II.
454.
=Division plates.=--What are division plates in boilers? II. 455.
=Intercepter.=--What is the separator or intercepter of a marine boiler?
II. 455.
=Boiler draft.=--What causes the draft in a boiler? II. 455.
=Rapid wasting.=--Where does the most rapid wasting occur in marine
boilers? II. 455.
=Coal consumption.=--About how much coal is consumed per square foot of
grate in marine boilers? II. 455.
=Short of coal at sea.=--If at sea and short of coal, what course would
you pursue in order to save coal and get into port? II. 455.
=Boiler relief in extreme danger.=--How would you relieve a marine
boiler in case of the safety valve being locked down from some
accidental cause, the engine also being disabled? II. 455.
=Pressure test.=--At what pressure should a new boiler be tested? II.
456.
=Boiler examination.=--State what you would consider a proper
examination, inside and out, of a marine boiler that had been in
sufficient service to require examining. II. 458.
APPENDIX--PART II.
DICTIONARY OF WORKSHOP TERMS.
A
=Addendum.= That part of a gear wheel tooth that extends beyond or
outwards from the pitch line.
=Addendum-circle.= The circle representing the full or greatest
circumference of a gear wheel.
=Adjustable reamer.= A reamer whose teeth may be adjusted to the
required diameter.
=Angle-iron.= A shape of wrought iron or steel having two flanges at a
right angle; thus, [L]
=Angle-plate.= A plate having surfaces at a right angle, one to bolt to
the machine work-table, the work being bolted to the other.
=Angle-tooth.= A gear wheel tooth that runs across the face of the wheel
in a line that envelops part of the wheel circumference.
=Angular cutters.= Cutters, whose teeth are on a circumferential
surface, that is, at an angle to the cutter axis, such angle not being
that of 90° to either the side face nor to the axis of the cutter.
=Angular-velocity.= Velocity measured in degrees of angle.
=Annular.= In the form of a ring.
=Apron.= 1. The piece that carries the tool port or clamp on an iron
planing machine. 2. The front plate of a lathe carriage.
=Arbor.= 1. A mandrel used to drive work upon. 2. A spindle or shaft of
a machine.
=Arc.= A portion of a circle.
=Archimedean drill= (är-k[)i]-m-[e.]-d[=e]'an) A drilling device in
which a nut moved endwise on a stock or handle causes the drill to
revolve back and forth.
=Arc of approach.= That part in the revolution of a pair of gear wheels
in which the teeth in contact approach the line of centres of the two
wheels.
=Arc of recess.= That part in the revolution of a pair of gear wheels in
which the teeth in contact recede from the line of centres of the two
wheels.
=Arc-pitch.= The pitch of gear wheel teeth when measured around the
pitch circle.
=Attachment.= A work-holding device that may be attached to a machine.
=Auger.= A wood-boring tool having two spiral plates and a pointed screw
to feed it, the cutting edge being at the end of the tool.
=Axle-box.= The bearing in which an axle revolves.
B
=Back-gear.= The toothed wheels on the spindle of a lathe and at the
back of the lathe-head, by means of which the speed of the lathe is
reduced.
=Back-geared lathe.= A lathe having a back gear to reduce its motion.
=Back-knife gauge-lathe.= A lathe in which the work is finished and cut
to size and shape by a knife at the back of the lathe.
=Balanced pulley.= A pulley whose weight is so equally distributed that
it will run steadily and smoothly at the speed for which it is balanced.
=Balanced valve.= A valve so constructed as to move with equal force in
either direction.
=Ball and socket joint.= A universal joint consisting of a ball on the
end of a shaft and in a casing that envelops it and yet permits it to be
moved in its casing.
=Ball-cutter.= A tool for finishing metal balls.
=Ball-pene.= A spherical pene of a hammer.
=Band-saw.= A continuous ribbon of steel having saw teeth on one of its
edges.
=Band-saw machine.= A machine for operating a band-saw.
=Bastard file.= A file whose teeth are one degree or grade coarser than
a _second_ cut file and one degree finer than a _coarse_ cut file.
=Belt.= A leather band employed to drive pulleys, for transmitting
motion.
=Belt-clamp.= A clamp for pulling the ends of a belt together, to lace
it, while the belt is upon the pulleys.
=Belt-hook.= A hook employed to fasten the ends of belts together.
=Belt-pulley.= A wheel that drives or is driven by a belt.
=Belt-shipper.= A device for moving a belt from one pulley to another.
=Belt-tightener.= A pulley employed to cause a belt to tighten upon
another pulley to enable it to transmit motion periodically instead of
continuously.
=Bevel-sawing machine.= A wood-working machine in which the saw or the
work table may be set to cut a surface at other than a right angle to
the face of the work that rests against the work table or the fence as
the case may be.
=Bevel-square.= A square whose blade may be set to any required angle to
the stock that holds it.
=Bevel-wheel=, _or_ =bevel-gear.= A gear wheel with its teeth at an
angle to its shaft.
=Bit.= 1. A boring tool. 2. A tool that is carried in a holder.
=Blank.= A piece of material roughly formed and ready to be formed into
some definite shape.
=Blast-pipe.= 1. The pipe conveying the blast or air to a fire furnace
or cupola. 2. A small pipe through which steam escapes up a locomotive
chimney to increase the draught of the fires.
=Blob.= An extremely loose place in a plate or saw blade.
=Block-plane.= A short plane.
=Boiler-shell.= The outer casing of a steam-boiler.
=Bolt.= 1. A holding device having a head at one end and at the other a
threaded stem to receive a nut. 2. A short piece of a round log.
=Bolt-cutter.= A machine for cutting screw threads upon bolts or similar
work.
=Boring-bar.= A bar that carries boring tools.
=Boring-machine.= A machine for boring holes in metal or wood.
=Boring-mill.= A form of lathe used mainly for boring.
=Boring-tool.= A tool for cutting out and enlarging a bore or hole.
=Boss.= An enveloping piece on an axle or shaft and having upon it an
arm, arms, or spokes.
=Bottoming-tap.= A tap having a full thread up to its very end so that
it will cut a full thread to the bottom of a hole.
=Box-chuck.= A rectangular two-jawed chuck used by brass finishers.
=Box-tool.= A tool used in screw machines and turret heads, and which
guides the work while it is being operated upon. A box tool in many
cases carries more than one cutting tool.
=Box-wrench.= A wrench which fits over the head of the bolt and passes
endways upon it.
=Brace.= 1. A rod, bar, or beam that braces or supports. 2. A device for
revolving cutting tools.
=Bracket.= A projecting frame that is bolted to its supporting pieces or
frame.
=Brad-awl.= An awl for piercing small holes in wood and having a
wedge-shaped end.
=Branch-pipe.= A pipe leading out of another.
=Brass-and-brass.= A term used to denote that the two brasses or boxes
of a bearing are locked together by the key, cap, or set-screw.
=Brasses.= Pieces fitted into a frame and intended to afford a bearing
for a journal.
=Break-lathe= _or_ =gap-lathe.= A lathe having a break or gap in the bed
and beneath the face plate to let chucked work of large diameter pass.
=Broach.= A toothed tool for cutting the walls of a hole.
=Broaching-press.= A machine that forces a broach to its cut.
=Bunter-dog.= A work-gripping device for a planing machine, and
consisting of a piece having a hook end to engage in the T-slot of the
table, and a set-screw to bind the work.
=Butt-joint.= A riveted joint in which the ends of the plate abut fair,
one against the other.
=Butt-strap.= A strip or band of iron employed to hold the joint
together in a butt-joint.
=Butt-weld.= A weld in which the end of one piece merely abuts against
the other when the two pieces are put together to weld.
=Buzz-planer.= A wood-planing machine in which the work is fed by hand.
C
=Calender-roll.= A roll for calendering paper.
=Caliper-gauge.= A gauge in the form of a solid caliper.
=Calipers.= A hinged tool for measuring work.
=Cam.= A revolving disc whose actuating surface is not a true circle.
=Cam-motor.= A cam together with the rod it actuates.
=Cap.= The plate or upper part of a bearing that holds the top half of
the box or brasses in place.
=Cape-chisel.= A narrow machinist's chisel.
=Caps.= The backward curves on the points of file teeth.
=Cap-screw.= A screw with a collar and a square head.
=Carrier.= A device for driving lathe work.
=Case hardening.= A process of hardening the surface of wrought iron,
the hardening usually extending about 1/32 inch in depth.
=Cat-head.= A sleeve fastened by set-screws to slender lathe work and
running in a bearing so as to steady the work.
=Caulking-tool.= A tool used for caulking riveted joints and in making
rust-joints.
=Centre-bit.= A bit having a triangular conical point with its cutting
edge on one-half of the end and a spur on the other half.
=Centre-punch.= A tool having a coned point for marking the centres to
work.
=Chamfer.= A facet that removes the corner of a right angle.
=Change-gears= _or_ =change-wheels.= The gear wheels employed to change
the revolutions of a lead screw or feed motion.
=Chaser.= A toothed tool for cutting threads by hand in a lathe.
=Check.= A crack.
=Check nut.= A second nut screwed against the first to check it from
slackening back.
=Chip-break.= A piece that rests upon the work of a wood-working machine
and prevents the cutter from splitting out the wood as the cut leaves
the surface.
=Chipping-hammer.= A machinist's hand hammer.
=Chips.= 1. The cutting from a metal cutting machine tool. 2. The thick
cuttings from a wedge-shaped wood-working tool, as from an axe or adz.
=Chisel.= A wedge-shaped tool.
=Chisel-tooth saw.= A saw having inserted teeth with a maximum of front
rake.
=Chop= _or_ =hammer-sink.= A mark left on a plate by a sawmaker's or
plate straightener's hammer.
=Chord-pitch.= The pitch of gear wheel teeth measured in a straight
line.
=Chuck.= A work-holding or tool-holding device.
=Chucked.= Held in a chuck.
=Chucking-lathe.= A lathe having a large face plate for chucking
purposes, and usually a short bed.
=Chuck-plate.= A large face plate on which work may be chucked.