TOOLS AND APPLIANCES.
WORKSHOP FITTINGS.
=229.= Before proceeding to describe the various forms of lathes and
the several small tools that the watchmaker should make for himself as
occasion offers, either during his apprenticeship or immediately after,
with a view to increase his manual skill or to extend his experience,
it will be well that he take note of the principal conditions that
should be satisfied by the ordinary tools that he will have to buy,
as well as the precautions to be observed in their use and some
improvements of which they are capable.
=230.= =The bench or board.= This should be fixed in front of a large
window that affords a good light. The various hooks, recesses, etc.,
for holding files, hammers, etc., as well as the drawers, should be
well in sight, not only in order that the hand can at once take hold of
whatever tool is required, but also to enable the workman to restore
them to their place immediately after use. By doing so he will have
no occasion to retain on the bench any but those tools that are very
frequently or continuously used.
It is an excellent habit, conducive both to well-planned and rapid
work, and which can be easily acquired by a little attention during an
apprenticeship, to always place the same tools in the same places, as
the bench will then never be encumbered. By this means loss of time in
turning over a number of objects in order to find one that may be small
is frequently avoided.
This observation is of minor importance to specialists who require but
a small number of tools; but it is of the first importance to a workman
that is engaged in the repair of watches.
=231.= =The stool.= Those with cane seats are to be preferred. The
height of the bench and stool should be so related that the muscles
of the chest are not too much cramped, especially if the workman is
engaged on an operation that occupies a long time and obliges him to
maintain a stooping position. The stool with a screw is advantageous in
this respect.
=232.= =The lamp.= Certain precautions in regard to artificial light
have already been indicated in article =218=.
=233.= =Oilstones.= It is impossible to maintain the points of
gravers in good condition if care is not taken to keep clean and flat
the surface of the stone on which they are set; if it has suffered
irregular wear, the level may be restored by rubbing the stone on a
flat, smooth board, covered with a thin paste of fine sand and water.
Most kinds of oil thicken on the surface rapidly, when the graver will
slide over without being ground down at all, turning around in the hand
and thus destroying the flat face and wearing the softer parts of the
stone, rendering it uneven. A strong solution of potash or soda is very
effective for removing this gummy mass; benzine is also recommended for
the same purpose. Various substitutes for common oil are used; such
as the mineral lubricating oils or petroleum. Dr. Latteux advocates
the use of a mixture of alcohol and glycerine, the proportion of the
latter decreasing as the extent of metallic surface in contact with
the stone at once increases. Thus, for example, in setting a razor the
stone will bite better if alcohol be in excess; but for a graver, of
which only a small surface touches the stone, the amount of glycerine
present should be relatively much greater.
=234.= =Circular oilstones.= Circular oilstones will be found very
convenient for sharpening drills, gravers and other cutting tools,
where it is desirable to have exact angles. An Arkansas or Turkey stone
dressed down to circular form, and say 1½ inches in diameter, when
mounted for the lathe will be found very useful. Apply the lubricant to
the stone the same as you would to a flat one, and hold your graver or
drill at the exact angle you wish the cutting edges to be and turn at
a moderate speed. Truer angles and better work can be produced in this
manner than by any other. Emery or corundum wheels can be mounted in
a similar manner. Small circular stones can be obtained from material
dealers and dental supply houses, in sizes varying from ½ × ⅛ to 3½ × ¾
inches. They can be mounted similar to Fig. 49, by turning down a piece
of No. 30 Stubb’s steel wire to the size of the opening in your wheel
and riveting the wheel firmly upon it. The best sizes for watchmakers’
use are ½ inch, 1 inch and 1½ inch in diameter.
[Illustration: _Fig. 49._]
=235.= =Small grindstones.= When it is necessary to remove a good deal
from the face of a graver, the operation will take too long on the
oilstone, and there would be considerable difficulty in maintaining the
flat face; recourse must then be had to the grindstone, but it should
be remembered that care is needful when using it. The grindstone must
always be thoroughly wet in order to avoid heating the graver, as its
cutting power would then be destroyed. The emery wheels described in
paragraph =165= can be used for this purpose, but they are, for the
most part, inconvenient on account of the rapid increase they occasion
in the temperature of the metal. Some forms of emery wheel can,
however, be moistened just as the grindstone.
When the cylindrical surface is rendered irregular by use, take a piece
of sheet-iron, the tail of an old file or a cold chisel, and hold it
with one hand firmly on a support against the edge of the stone, which
is rotated by the other hand. The surface can thus be made smooth and
true, providing it is only attacked gradually and the handle is not
turned too rapidly. An excessive velocity will heat the iron, which
is then less effective and is more rapidly worn down; whereas, with a
slow motion, the iron will relatively wear little and the stone more.
A rough diamond mounted at the extremity of a steel rod, affords an
excellent means of trimming a grindstone, and is at the present day
generally used in factories.
=236.= =Glasses.= Some particulars have already been given in regard to
these simple microscopes in article =218=.
=237.= =Files.= A new file should never be used for steel; it is best
to employ it for some time at first on brass, taking care not to use it
too roughly. If employed to steel at once, or if sharp, quick strokes
are applied, the cutting edges of the file will chip off, and the hard
particles will be embedded in the metal operated upon; the work will
thus be bad, and the file itself deteriorated. A file that has been
carefully used, and has passed gradually from brass to steel, will last
four or five times as long, and will always work well.
Watchmakers often fit files into handles by driving them firmly into
round holes in the handles; this practice frequently leads to the
handles being cracked, and the following method is preferable: Take
an old worn out file or a piece of iron of the same form as the tail
of the file to be fitted; heat it several times to bright redness and
drive it, when so heated, into the handle, taking care to maintain it
perpendicular. A hole will thus be made of the required form, in which
the file will hold without there being any occasion to apply excessive
force in fixing it in position.
When the surface of a file is choked with particles of iron, copper,
wood, etc., while the cutting edges are yet good, it can be cleaned as
follows: Place the file for a few seconds in a hot lye of potash in
water, and on withdrawal, dry it before the fire and brush the surface
with a stiff brush.
=238.= To renew the cutting edges of files, either of the following
methods can be adopted: 1. First clean the file with potash or soda
dissolved in water, if greasy or resinous substances have to be
removed; with hydrochloric acid if it is rusty; and by rubbing with
a metallic brush or piece of coke if particles of iron, brass, lead,
copper or tin have to be removed. The file is now immersed in a
mixture of 1 part nitric acid, 3 parts sulphuric acid, and 7 parts
water. As the action of the acids become less energetic owing to the
combination with iron, the temperature of the mixture must be raised,
since rapidity is a condition of success. The time during which the
file should remain in this bath varies from 10 seconds to 100 or more,
the roughening of fine-cut files being far more rapid than when they
are of a coarser cut. On removal from the bath, immerse in lime wash,
dry, and then cover them with a mixture of oil and turpentine by means
of a brush, after which they are ready for use. 2. After being cleaned,
as explained above, the file is supported in a dish full of water,
resting on two cross wires, so that all its surface is in contact with
the liquid. Now add strong nitric acid in the proportion of 1 part to 8
of the water, mix it thoroughly and allow it to remain for 25 minutes.
Remove the file, and, after washing in water and rubbing with a hard
brush, place it again in the bath, to which a second eighth part of
acid is now added, and leave it for 50 minutes. Again remove and brush
the file, add a sixteenth part of concentrated sulphuric acid, and
replace the file in the bath. Then wash successively in pure water and
in lime wash (to remove the last traces of acid), and dry. The file
will be found to possess both the qualities and the appearance of a new
one.
=239.= _To cut an equaling file._ It often happens that a workman
is called upon to modify the shape of, for example, the bottom of a
rectangular notch, and he is not provided with a file of suitable
shape. In such a case he can adopt one of the following methods of
extemporizing a file:
[Illustration: _Fig. 50._]
1. Clamping the small steel strip, L, Fig. 50, in a vice, cut the
notches with a chisel, _n_, as follows: Holding _n_ a little inclined,
cut the first notch, _i_. This will slightly raise the metal,
presenting a rounded face at the back. To make the next cut, hold the
chisel with its edge on L and, after drawing it backward until arrested
by the back of _i_, incline it to the requisite amount and give a
second blow with the hammer, then continue the operation till the whole
is finished. A few trials will enable any workman to make a small file
with sufficient accuracy for his purpose.
2. Employ an arrangement similar to that of the micrometer divider
(=44=) only more rigid. A study of this article and examination of the
corresponding figure will afford all the information that is necessary.
3. This is identical with the method of dividing a rule described in
=46=, except that the divisions are closer together and the tracer is
replaced by a revolving cutter with its axis a little inclined, to give
the requisite slope to the teeth of the file. This cutter is supported
in a hinged frame and provided with a washer of ivory or other such
substance, as seen at _s_, Fig. 50, to determine the depth of cut.
=240.= _Beaupuy files and burnishers._ Most watchmakers are acquainted
with the files and burnishers that M. Beaupuy has introduced for
rapidly forming conical pivots, the main characteristic of which is
that the corner presented to the pivot is rounded to the desired form
and roughed; they do their work rapidly and well, but some skill is
necessary in their management. To the instructions which accompany them
we would add the following:
They must never be used when quite new on a pivot that is to be
employed in a watch; it will be reduced too rapidly. The freshness must
be worn off the cutting edges of the teeth by preliminary use.
The pressure must only be applied perpendicularly to the surface of the
staff as in making a square-shouldered pivot; the file is held against
the flat surface without pressure. A lateral force will have the effect
of straining the pivot and causing it to break.
=241.= =Pliers, tweezers, etc.= It is advisable to have a considerable
number of these, as their strength should always be proportional to the
force that has to be applied to them. For example, if a pair of sliding
tongs is used when a hand-vise is needed, the former will be strained
beyond its limit of elasticity and the tool becomes nearly useless.
The same might occur with any other form of pliers or tweezers. In the
hands of a good workman they will last for a long time, but if used
unintelligently, without proportioning the size of tool to the force
that has to be applied, taking up the first that comes to hand, all the
tools will soon become unsatisfactory and the work itself will suffer.
It is very desirable to have one or more pairs of brass pliers and
tweezers for handling metal work without the risk of scratching.
=242.= =Compasses, gauges, micrometers, etc.= The common compass
for measuring thickness, the douzieme gauge, is not always strictly
accurate in its indications. The douzieme proper, has a scale
divided into twelfths, though some patterns are now made that have
a scale divided into tenths and hundreds of an inch and again there
are others that measure the fractions of a millimeter. The greater
majority of these tools on the American market are correctly divided,
but we sometimes come across those of foreign make that are divided
incorrectly and care should be used in selecting. In the inaccurate
tools the objection is that the opening of the jaws gives a measure of
a _chord_ whereas the displacement of the index measures the _arc_ of
a circle. It follows from this, that, if the index is first arrested
when pointing to 15, for example, and again when at 30, the interval
between the jaws in the second case will not be exactly double the
first. Before purchasing, it is well to test the gauge for accuracy in
this regard by some reliable standard.
=243.= _Caliper for mainspring height, depth of sink, etc._ A simple
instrument for taking such measurements is shown at G, Fig. 51.
[Illustration: _Fig. 51._]
The finger _a_ travels over a graduated arc whenever the rod _c_ is
pressed inwards; _b_ is a fixed stop, with its extremity in the plane
of _n_. Any movement of _a_ below _o_ measures the space traversed by
_c_ within the line _b n_.
Laying a coiled mainspring, for example, on a plane surface, stand the
base _n_ of the caliper upon it, and the end _c_ pressing on the table
will be forced upwards and move the needle. To take the depth of a
barrel, press _c_ on the bottom, allowing _b_ to rest on the edge of
the cover recess.
It will be evident, from the figure, that _a_ and _c_ are connected by
a spring passing around drums at corresponding axes. The smaller _j_
is, the more sensitive will the instrument become.
=244.= =Figure 8 caliper.= For ordinary work, the calipers to be
bought at material stores will suffice; but when it is required to
verify escape wheels, balances, etc., there is some risk of accidents
in consequence of the variableness of the friction at the joint. To
remove this source of danger, true the rubbing surfaces in the mandril
and replace the brass discs at the center by similar discs of steel,
then carefully re-make the rivet that forms a hinge, after oiling all
the acting surfaces. The arms will now move with a uniform degree of
stiffness, so that there need be no danger of jerks.
=245.= =Riveting stake and punch.= The holes in a riveting stake are
made to increase downwards, so as to avoid any accident occurring
through the oscillation of the axis. The riveting punches made of a
plain steel rod, with a hole drilled at one end in the direction of the
axis, are the best. Those that are perforated transversely like the
lanterns of screw-point tools, do not produce such good riveting, since
the parts of the end, from behind which metal has been removed, are
more or less elastic.
=246.= =Burnishers.= Burnishers will not remain in good condition
unless their surfaces are prepared, from time to time; in the case of
those used for very fine work, by passing over a buffstick charged with
polishing rouge or very fine emery, and other kinds on an emery stick
more or less fine, according to the degree of roughness the burnisher
is required to possess.
=247.= _To re-face a burnisher._ Pivot burnishers are usually re-faced
by a lapidary; a watchmaker can, however, do it for himself very
effectually in the following manner: Prepare a dry, smooth piece
of wood, rather thick, and of a width equal to the length of the
burnisher. On this board carefully glue a piece of emery paper, of a
fineness corresponding to the degree of cut required, stretching it as
even as possible, and turning the edges down towards the under side.
Then lay the board on a firm smooth surface, resting a weight upon it,
and allow it to dry.
In using this lap, it is fixed or allowed to rest against the side of
the bench; holding the burnisher with two hands at its extremities, the
workman places himself at one end of the board, and draws the burnisher
along it towards him, maintaining the surface quite flat and applying
considerable pressure. On reaching the nearer end, raise it, and after
again placing it on the farther end, draw towards the body, and so on.
By proceeding in this manner and always in the same direction, placing
the burnisher so that the acting edge is farthest away from the
operator, all risk of rounding this angle will be avoided.
=248.= =Broaches.= Great care is needed in adapting handles to
broaches. Resting the point against a finger of one hand and causing
the handle to rotate by two fingers of the other hand, the broach
itself should be seen to remain true.
It is a good precaution, suggested by M. H. Robert, to gently draw a
piece of iron, charged with rouge, along the edges of pivot broaches in
order to remove the thread of metal from them. Minute particles of this
thread would otherwise remain in the holes, and occasion wear of the
pivots.
These fine broaches are not fixed in handles, but a piece of
sealing-wax is melted on to the upper end; then, holding the broach
between the fingers, with its stem downwards, it is rotated while held
to a flame, so that the sealing-wax forms a regular, oblong handle.
=249.= =Blow-pipes.= In order that a long even flame may be obtained,
the hole should be of moderate size and perfectly clean around the
edge; otherwise the jet cannot be straight and sharp. Difficulty will
always be experienced by anyone who has not learned to breathe without
interrupting the continuity of the blast. Where a supply of gas is
available, the gas blow-pipe presents advantages from the point of view
of convenience.
[Illustration: _Fig. 52._]
Fig. 52 shows a gas blow-pipe for jewelers, which is simple and
convenient. It consists of a blow-pipe of the ordinary form, having a
gas pipe inserted in the lower half, and a threaded hood or sleeve at
the lower end, which changes the shape of the flame by screwing in or
out, so as to vary the influence of the current of air upon the flame.
A ring adapted to slip over the finger while working, is soldered to
the middle joint of the pipe, and the quantity of gas is controlled by
the stop-cock and spring lever shown in the cut, the gas being supplied
to the pipe by a rubber tube connecting it to the nearest gas jet in
the usual way. Thus having the shape of the flame under control and the
quantity variable at will, the workman is in position to accomplish the
desired end speedily and effectually.
To use to the best advantage, set the jamb-nut so that with the valve
lever in its normal position, the flame at the end of the pipe will
just keep alight. The blow-pipe can then be laid down temporarily and
again used without the trouble of turning off the gas or relighting.
When used as a mouth blow-pipe, the most convenient way to hold it is
with the third finger through the ring. For bellows work it is better
to pass the ring over the index finger. The ring also serves, with the
valve-lever, as a rest to hold the flame-nozzle away from the table
when the blow-pipe is laid down temporarily.
To produce an oxy-hydrogen flame, connect the air-pipe with a cylinder
of nitrous oxide, opening the cylinder-valve carefully, so as to
permit the escape of only sufficient nitrous oxide to produce with the
illuminating gas a very small flame. Regulate the illuminating gas flow
with the thumb-screw or with the finger on the lever of the blow-pipe
valve.
[Illustration: _Fig. 53._]
Fig. 53 shows an automatic hand blow-pipe for use with a foot blower.
One of the rubber tubes shown is connected with the blower and the
other to the gas supply. It is self adjusting for both gas and air,
requiring only a slight motion of the lever, shown under the thumb, to
obtain instantly any flame, from the smallest to the largest; so that
these pipes have all the delicacy of the best mouth blow-pipe, used
with the utmost skill, together with the power and advantages obtained
with a mechanical blower.
=250.= =Small gas furnaces.= The workman will frequently have occasion
to anneal pieces of steel or to raise to a red heat objects that are
too large for the blow-pipe; an ordinary open fire aided by bellows is
often resorted to in such a case. A better plan, however, is to use
any small portable gas furnace, provided with a hood that completely
closes it at the top.
Fig. 54 shows a gas melting furnace, which is kept by material and
supply houses. It is powerful enough to melt gold, silver, brass and
copper, but is not recommended for cast iron. It can be used for
scorifying and cupelling. The lid can be pushed sideways sufficiently
to give access to the interior of the furnace.
[Illustration: _Fig. 54._]
The following points in the management of a gas furnace will be
of service to all novices in their use. The power and speed are
practically without limit, depending only on the gas and air supply,
and are under perfect control. Allowing five cubic feet of gas for
heating up, it requires about four feet of gas for every pound of cast
iron melted. For small work it is as cheap as a coke furnace, and not
one-quarter the trouble.
The quantity of air required depends upon the gas supply. One must
be equal to the other, so that perfect combustion will take place,
and that entirely within the furnace. An excess of either gas or air
renders a high temperature an impossibility.
See that all gas taps have a large clear way through. High temperatures
and rapid working require a free supply of gas.
To adjust a new furnace to its highest power, connect both gas and air
supply with the burner. Turn on the full gas supply, light the gas, the
air-way being full open, work the foot blower and then put the gauze
nozzle of the burner tight against the hole in the casing, so that no
flame escapes around it. If the flame comes out of the lid about two
inches, the adjustment is right. If the flame is longer, open the air
check until the proper flame is obtained, or reduce the gas supply. If
smaller, or not visible, close the air check until the flame appears.
The cap-nut, which will be found at the throat of the horizontal
“mixing tube,” where the air enters and mixes with the gas, is used for
changing the size of the orifice from which the gas escapes. When the
escape is from a large orifice, a smoky, yellow, or “reducing” flame
is the result. By contracting the orifice by screwing the cap-nut on
to the gas delivery tube, a blue or oxidizing flame will be obtained.
Adjustment for the proper flame should first be made by this nut, and
the size of the flame regulated afterwards by means of a cock at the
gas main. A slightly yellow flame gives the best results when a high
heat is desired. The arrangement above described is clearly shown at
the left-hand lower corner of the sectional illustration above.
A chimney or stove-pipe 8 or 10 feet high may be used as a fixture,
and the draft partially stopped by the damper or slide when lower
temperatures are required, the gas being turned down in proportion; the
guide for the proper adjustment being that UNDER ALL CIRCUMSTANCES THE
FLAME MUST JUST COVER THE CRUCIBLE OR MUFFLE, but not extend into the
chimney so as to make it red hot. When the flame covers the crucible
or muffle, the gas is doing its extreme duty under the most favorable
circumstances, without waste.
Keep all fluxes away from the furnace jacket, as they are injurious
to fire clay, and are liable to cause the lids, etc., to stick to the
furnace.
A thin layer of quick lime on the bottom of the furnace will prevent
the crucible adhering to it when very hot.
When using a furnace for high temperatures, care should be taken not to
use a fire clay casing, as it melts at a temperature a little above
that of cast iron; plumbago or asbestos only should be used when very
high temperatures are required.
[Illustration: _Fig. 55._]
Fig. 55 represents a small gas furnace, which is extremely useful for
small meltings, experimental work, etc. It consists of a pot made of a
mixture of fire clay and asbestos, bound with rivetted iron hoops, and
having a hole in the side at which the flame enters. A lid pierced by a
central hole permits the escape of the products of combustion, and the
crucible is placed in the center so that the flame surrounds it. It is
worked with gas and a foot blower. Gas from a ⅜-inch supply pipe will
work it efficiently. About ten cubic feet of gas per hour is sufficient
for most purposes.
The casing holds the heat so perfectly that the most refractory
substances can be fused with ease, using a Fletcher foot blower. Half
a pound of cast iron requires from seven to twelve minutes for perfect
fusion; the time depending on the gas supply and pressure of air from
the foot blower. The crucible will hold about ten ounces of gold.
The power which can be obtained is far beyond what is required for most
purposes, and is limited only by the fusibility of the crucible and
casing.
[Illustration: _Fig. 56._]
Fig. 56 represents a small apparatus, which, owing to its speed and
economy of operation, has a very extended use in the jewelry and
silversmithing trades. With this apparatus a sound two-ounce ingot of
gold or silver can be moulded in two minutes. A crucible of moulded
carbon is supported by a sheet-iron slide, or plate, which is clamped
to an ingot mould by a clamp which swivels in the U-shaped cast iron
stand. The metal to be melted is placed in the crucible, and the flame
of the blow-pipe directed on it until it is perfectly fused. The whole
is then tilted over by means of the upright handle at the back of
the mould. The waste heat serves to make the ingot mould hot. No flux
should be used with the carbon crucibles. For the smaller operations,
such as making small quantities of colored golds, for electroplating
solutions, testing ingots, and the smaller operations of the jeweler
and plater, it is invaluable.
[Illustration: _Fig. 57._]
The air pressure used in operating gas furnaces varies from one to
four pounds per square inch, though the latter is seldom required
except for the severest work in large furnaces; as a general rule it
is less than two pounds in the operations of the gold and silversmith.
The pressure must be arranged so that the air supply equals that of
the gas used. This can be readily seen by the color of the flame, as
noted in instructions for handling the furnaces. For small operations
foot blowers are used. These consist of a powerful bellows having a
hemispherical pressure chamber on one side, and adapted to work either
by the hand or foot; see Fig. 57.
[Illustration: _Fig. 58._]
[Illustration: _Fig. 59._]
The perfect combustion of the gas is secured by mingling equal
quantities of gas and air in a mixing chamber, and then igniting the
mixture. In the larger furnaces this is accomplished by a mixing
chamber placed under the furnace, so as to heat the mixture before
ignition, and no pressure supply of air is necessary. In the smaller
apparatus, this mixing is done in the burner, which consists of an
inner tube carrying an air supply, surrounded by a gas tube, and the
whole surmounted by a sliding nozzle for changing the shape of the
flame. The mixing chamber being so small, the air and gas pass through
it so rapidly that considerable pressure of air must be provided to
prevent it from being excluded by the normal pressure of the gas; hence
the necessity for a blower when using small burners.
When it is not desirable to use gas, for pecuniary, or other reasons,
melting may be carried on by means of a gasoline gas flame, which is
noisy, but otherwise little inferior to coal gas. The furnaces for
gasoline differ but little in construction from the others, as will be
seen by Figs. 58 and 59. The only difference being that the burners are
applied from the side and no air pressure tubes are needed, while the
furnace is supported on legs to insure safety from fire.
[Illustration: _Fig. 60._]
The burner for gasoline is radically different from that for gas,
being, in fact, a small gas machine, Fig. 60.
In Fig. 60 _P_ is an ordinary force pump, at the bottom of which, at
_A_, is a valve which closes automatically upon releasing the pressure
from the pump, _C_ is a check valve which closes the inlet to the tank
_T_ completely; _F_ is a filling screw for introducing gasoline. _V_ is
a vent screw for letting off the pressure when through; _H_ is a pipe
leading from the tank to the burner _D_; _E_ is the burner regulator,
terminating in a fine point, closing the orifice of the burner; _S_
_S_ are packing boxes. Upon opening _C_ and pumping a few strokes
a pressure is created in the tank and on top of the fluid, forcing
it through the tubes of the burner, which being previously heated,
vaporizes the gasoline. This issues from the orifice at the end of _E_
as a highly heated gas and burns as such in the form of a powerful
blast, Fig. 61. After being once started the heat of the flame passing
through the burner, vaporizes the fluid in the tubes, and hence the
apparatus is automatic.
[Illustration: _Fig. 61._]
The air which is forced in is not consumed, so that to keep up the
blast it only requires a few strokes of the pump occasionally to
maintain the pressure lessened by the consumption of the fluid.
To operate the blow-pipe: close _E_; unscrew _F_, and introduce from
two quarts to one gallon of gasoline of 76° according to the capacity
of the tank. Replace _F_ and close _V_; open _C_ one or two turns and
give three or four full strokes of pump _P_, and close _C_. Heat the
burner by burning some of the fluid in a suitable vessel placed under
the burner; when hot enough apply a match and open _E_ gradually, until
the action is more or less uniform. If no spray or liquid issues from
the orifice, the burner is hot enough; if not hot enough, burn slowly
until no liquid or spray issues. When sufficiently heated the blast can
be made of any intensity desired, by the use of the pump as above. To
stop its action, shut the regulator _E_, or open screw _V_, or both.
When not in use the vent _V_ should invariably be kept open. The mouth
of the burner _D_, should be two or three inches from the inlet of the
furnace, or there will not be perfect combustion.
For very high temperatures and muffle work, light the burner as above
and heat the inside of the furnace to a bright red; then place the
burner against the inlet of the furnace; turn out the burner by means
of the cock _E_, and immediately turn it on again without lighting
it, when if the furnace is hot enough, the gas will ignite inside the
furnace. The heat can be regulated as in the first method of burning.
When burning inside of the furnace, there must be no flame in the
burner tube; it should all be inside the furnace, and the tube of the
burner must be close to the fire hole, or there will not be enough heat
in the tubes.
Use a drop or two of sperm oil on the piston of the pump occasionally,
also on leather washer at _F_, otherwise the apparatus will be apt to
leak, corrode and work badly.
[Illustration: _Fig. 62._]
=251.= =Muffle Furnace.= This consists of a fire-clay furnace, mounted
upon a powerful gas burner and containing an oven, also of fire-clay or
plumbago, so placed as to receive the full heat of the flame, without
permitting the direct action of the flame upon any object placed within
it. The objects are placed in and withdrawn from the muffle, or oven,
through the door shown in the cut. This door is made of two pieces so
that the upper one may be removed to watch the progress of the work
without chilling the contents of the muffle by too great an entrance
of cold air. They are extensively used for assaying, annealing, etc.,
and for many other purposes where an exact temperature is required. The
illustration shown in Fig. 62, is of a gas muffle, but they are also
made to be used with the gasoline burner previously described.
THE LATHE.
=252.= Of all the tools and machinery employed by the watchmaker, the
lathe is the most important. Very poor work is often turned out by
those possessing a first-class lathe, but there are very few persons
who can turn out good, true work, from a poor, cheap lathe, and if it
is untrue it is utterly impossible to turn out good work. Wonders can
be accomplished by the ingenious mechanic who thoroughly understands
the capabilities of the lathe. By patient skill of manipulation, the
Chinese and Japanese turn out some truly wonderful work; they succeed
in turning sphere after sphere, one inside the other, from a solid
piece of ivory, the opening from one to another being comparatively
small.
The earliest form of the lathe in the trade was the dead center: that
is, a lathe whose parts did not revolve, the object to be operated
on being placed between centers and made to revolve by means of the
bow. This form of lathe was succeeded by the live spindle or live
mandril pattern, although there were many good points about it that
must be acknowledged. It contained one great element that many modern
appliances, termed lathes, lack, i. e., the element of truth. No matter
how coarsely or crudely constructed, this truth was not eliminated,
except by the ignorance of the artisan, for the centers must remain
the same relatively, whatever may be their position in relation to the
lathe bed.
With the introduction of the live spindle lathe in this country, the
verge, Jacot and other lathes and tools of that type were rapidly
abandoned. In Europe, however, the live spindle lathe did not meet
with such a cordial reception, and it has taken many years, in some
localities, to overcome the prejudice against them; in fact, there are
still many workmen there who cling to the dead center patterns.
The all-important point in lathes of the live spindle type is
accuracy of fitting, and particularly in regard to the spindle and
its bearings, for unless a certain degree of perfection is attainable
in this particular, it is worse than useless, as it not only does not
do the work, but leads the artisan astray. The workman, sometimes,
through motives of economy, purchases foreign made lathes, that
closely resemble the American in outline and finish. These lathes,
as a usual thing, are not accurate, and in the greater majority of
cases the chucks which accompany them are worse than nothing, and yet
these lathes, in nearly all cases, are declared to be as good as the
American. There are some foreign lathes that are very carefully made,
and are quite as true as the best American, but they are the exception
and not the rule. The workman who buys one of these lathes cannot, of
course, tell whether it is right or wrong until he has placed it on his
bench and tested it, and even then he cannot be sure, for although when
a certain chuck is placed in the spindle and tested it may apparently
show no deviation from truth, there may still be untruth in the spindle
or chuck or both, as the errors in one may be counteracting the errors
in the other, and if the chuck be turned or an absolutely true chuck
placed in the spindle, the error will be made quite apparent. If an
American lathe, by any possibility, is allowed to pass the inspector,
and finds its way upon the market, the maker is only too glad to
replace it with a perfect one, for his reputation is at stake; but if
one of the imitation pattern proves untrue you will have to do the best
you can.
[Illustration: _Fig. 63._]
There are American made lathes upon the market that are as inferior in
many respects as the imitations, and the watchmaker will do well to do
without a lathe until such time as he can afford to purchase one of
known reputation. Among the first-class American lathes upon the market
may be mentioned the Webster-Whitcomb, shown in Fig. 63; the Moseley,
shown in Fig. 64; the Hopkins, shown in Fig. 65, and the Rivett, shown
in Fig. 66, and others.
An excellent lathe for the heavier work of watchmakers and jewelers,
such as cannot be performed with satisfaction on the watchmaker’s
lathe, is the No. 4 Barnes, which is shown in Fig. 67.
[Illustration: _Fig. 64._]
For screw-cutting, the manufacture of watchmaker’s tools, fishing
reels, repairs on tower clocks, in fact, all the heavier work of the
trade, it is admirably fitted.
=253.= =Care of the Lathe.= The American lathe of to-day is a marvel
of completeness in its parts, and how many hours, yea months, of study
and experiment have been bestowed upon it by its projectors and makers
to acquire these points of utility and excellency? What a vast amount
of care has been exercised for the production of a perfect lathe!
Must this care cease at the moment it passes into the hands of the
watchmaker?
It is a very easy matter at any time to wipe off the dust and oil that
may accumulate, but does this alone constitute due care? There may be a
nice glass case to cover it and keep off the dust, and a very good idea
it is, if faithfully used; but if a counter shaft is on the bench, or
much lathe work is to be done, it soon falls into blissful desuetude,
or finishes its usefulness by being broken. Then, often, a cloth is
wrapped about the lathe, which soon gets soiled and looks badly, let
alone the poor protection it affords.
[Illustration: _Fig. 65._]
Dust is omnipresent, and the greatest enemy to all active machinery;
it insidiously makes its way into every crease and crevice, and if not
promptly removed will cause untold damage. We cannot get rid of it and
must (like the industrious housewife) wage a constant warfare against
it.
The care necessary to be given to a fine lathe differs from most other
tools; it is not confined alone to the removal of dust and keeping
clean, but the fitting properly of the several parts as used. There
should be no overstraining when tightening screws, chucks, etc., or
when fitting articles in both wire and wheel chucks, and so on through
the list.
[Illustration: _Fig. 66._]
The face of the lathe bed when it comes from the makers is (or should
be) perfectly true from end to end, in order that head and tail stocks
will meet on a direct line of centers, even should they be changed
end for end, and a good lathe will meet those requirements. Now, it
is obvious to any thinking mind that if this face becomes injured by
neglect, whereby the nickeling is removed in spots or portions, they
will, in all probability, become rusty; this rust will then eat away
and throw off more, and soon the face presents an uneven surface, which
will tend to destroy the line of centers between head and tail stocks.
The head stock, usually occupying one position, causes less wear at
this point or place, while the hand-rest and tail stock are constantly
being shifted, so where there is more motion or action there must be
more wear, especially if dust, chips, or grit be allowed to accumulate
beneath them, and though the wear is seemingly imperceptible, it
nevertheless is there, and will sooner or later manifest itself, and
this is a signal that the level of the bed is becoming impaired, and,
necessarily, the truth. Thus too much care and attention cannot be
exercised in guarding against chips and dust when sliding hand-rest
back and forth on the bed.
[Illustration: _Fig. 67._]
At the end of the bed, where the tail stock takes position, many
watchmakers have the tail stock off, and this portion is more exposed
to atmospheric action, also receiving perspiration from the hands
when they come in contact. Again, others let the tail stock remain in
position, only removing when it comes in the way. In the former case,
it is well to devise some means for the protection of the bed; this is
easily done by making a sheath of chamois skin to slip tightly over
the bed; it can be removed and replaced readily, and when it becomes
soiled, can be washed.
This sheath should be fully two-thirds the length of bed, or reaching
from tail end up to hand-rest when it is close to head stock. It
preserves the bed from dampness, which is considerable in some
climates, also the perspiration of the hand and flying chips and dust.
In the second case, if the tail stock is allowed to remain on the
lathe, or, if removed and placed on the bench, it is subjected to all
the evils the bed is in the former. Our opinion is, the tail stock
should be kept in its compartment in a tight-fitting drawer, away
from dust and accidental knocks of other tools on the bench; the tail
spindle not being nickeled, is more liable to rust if left exposed, and
should be kept in a sheath of oiled paper. This may seem superfluous
and too much bother, yet it is taking proper care which tells in the
end.
The bottom of tail stock should always be brushed off before placing in
position, not only for its protection, but for fear some particle of
grit may be adhering, thereby throwing it out of truth, and screwing it
down tight only adds injury to the lathe if allowed to remain.
The head stock demands close attention; the spindle should run freely
without end-shake, and about once a week should be speeded, meanwhile
administering oil until it leaves the bearings clean, and then wiped
off. A little oil should be added every day. See that the mouth of the
spindle is kept bright and clean; thrust a piece of cloth clear through
spindle every now and then, that all dust and dirt may be removed.
Wire and wheel chucks should often be washed in gasoline to remove
gummy dirt and oil which is constantly adhering, and it is even well
each time a chuck is used, to wash off first, then wipe dry. A little
dirt on the mouth of spindle, or on the chuck, often throws it out of
truth, and consequently the article fastened therein also.
When fitting head or tail stocks, or in fact any attachment, do so
carefully. Do not bang it in place as if you held a grudge against it,
and when in position see that they are tightly screwed in place.
Having too much end-shake on live spindle, especially in soft lathes,
causes uneven wear in its bearings, besides not being reliable for true
pivoting or any such work.
When the cost of a lathe is taken into consideration, it goes to prove
that it is not easily replaced. Where is the jeweler with a stock of
goods who would retire without first seeing that his valuables were in
the safe, but how many are there that think of giving this protection
to their lathes? Some do, but the greater per cent do not. It is a good
plan to see that the head stock, the tail stock, and attachments are
in the safe and should a fire break out that endangers the store, and
no chance to save it, the feeling of satisfaction is great to know the
lathe is safe, that is, the most expensive parts, for the bed can be
purchased at a nominal cost compared to the attachments.
THE FOOT WHEEL.
[Illustration: _Fig. 68._]
=254.= In the selection of a foot-wheel the workman must be governed
by his own experience and taste, for the variety that exactly suits
one person is very distasteful to another. The swing treadle pattern
shown in Fig. 68 is a very popular one with American workmen. These
swing treadles are made in various ways by the different manufacturers,
but the methods of using them are alike. There are workmen, however,
who prefer the heel and toe motion and others that prefer the up and
down motion. This is all a matter of taste and it matters but little
what form of lathe wheel is used provided the motion is steady and the
exertion is light. As a general rule a heavy wheel, say forty pounds in
weight, will be found, on the whole, much better than a light one and
the motion will be more uniform.
=255.= =Driving Bands and Belts.= Most foot-wheels are so constructed
that either a flat or round belt may be used in transmitting the power
to the countershaft or lathe, as the case may be. Many watchmakers use
a flat belt between foot-wheel and countershaft and a round leather
belt, or cord, between countershaft and lathe. If we may judge by
appearances, this is the favorite fitting. Others use round leather
belts in both instances, while others again use cotton or hemp cord or
gut. All things considered, the round leather belt seems to possess
advantages over all others. It does not slip as easily as cotton cord,
is more elastic than gut and throws less strain on the bearings,
absorbs less power and works much smoother. The ends are fastened
together by means of an S hook and the cord may be readily tightened by
giving it an additional twist or two.
[Illustration: _Fig. 69._]
=256.= =The Countershaft.= The countershaft is indispensable in using
milling tools, wheel cutters and pivot polishers. The pattern shown in
Fig. 69 is but one of many on the market.
In some of the patterns the uprights extend through the top of the
bench and are held securely in place by means of thumb screws or wing
nuts. The pattern shown in the illustration is mounted on a solid metal
base which is intended to be fastened to the bench by means of screws.
The advantages of using a countershaft are three fold: First, you are
able to regulate your speed perfectly without changing the motion of
the foot from fast to slow or vice versa; second, your belt is carried
to the back of the bench, where it is out of the way, instead of
coming down in front of the head; and third, you obviate the necessity
of having holes in your bench on each side of the lathe, that small
articles are liable to drop through. Fig. 70 illustrates the favorite
arrangement of foot wheel, countershaft and belts.
THE BENCH.
[Illustration: _Fig. 70._]
=257.= As previously suggested (=230=) it is of the utmost importance
in doing good work, and doing it rapidly, that your bench be kept
orderly and clean at all times, and that all your tools and devices be
in their proper places, exactly where you can put your hand on them at
a moment’s notice. An excellent arrangement for a watchmaker’s bench
is shown in Fig. 70. This bench was designed by G. W. Laughlin, and
is complete in every detail. Benches can be purchased ready made from
material dealers, both with and without curtain tops, but there are
many watchmakers that prefer to make, or have made for them, a bench
varying from the usual pattern. The bench illustrated is made of black
walnut, veneered with French walnut and bird’s eye maple. The top is 21
inches wide by 41 long and is 33 inches from the floor. The drawers on
the right-hand side are 10 inches wide. In the center are two shallow
drawers, while the left-hand side is entirely boxed in.
IDLERS.
[Illustration: _Fig. 71._]
[Illustration: _Fig. 72._]
[Illustration: _Fig. 73._]
=258.= Idlers are especially valuable for use on slide rest tools,
such as pivot polishers, milling attachments, wheel cutters, etc.,
and with traverse spindle tailstocks, traverse spindle drivers, etc.,
to give a vertical direction to the belts. Idlers are constructed in
various forms, some of them being mounted on upright posts, fastened to
the bench just back of the lathe, as shown in Fig. 71; others consist
of steel rods terminating in a ball, and socket joint, where it is
fastened to the bench, as shown in Fig. 72, while in other patterns
the rod is fastened by means of a wing nut to a brace running from one
to the other of the supports of the countershaft and may be placed
at any desired angle. The idler shown in Fig. 73 can be used in this
way. Some watchmakers prefer to place their idlers on an overhead
countershaft, which is usually fastened just back of the bench and
about two and a half or three feet above it. The idler shown in Fig.
72 can be screwed to the bench or to the wall above the bench, in the
latter case it will extend out horizontally over the lathe and is out
of the way of the watchmaker when not in use. In the forms shown in
Figs 71, 72 and 73 the belt passes from the countershaft over the idler
and one long belt only is used. This style is sometimes varied by using
two separate belts one from the countershaft to the idler and another
from the idler down to the lathe. If in the latter style, a cone pulley
of rubber is used on the countershaft and also for the corresponding
pulley on the idler and a plain pulley for the down belt. Of course in
this form the idler stand must be in the form of a countershaft, as the
pulley must be fast on the shaft and the shaft itself must revolve. In
the styles shown above, the shaft is rigid and the pulleys revolve upon
it. The advantage of using the cone pulley style is that the speed of
the cutter or other attachment may be varied at will without in any way
increasing or decreasing the speed of the wheel.
CHUCKS.
[Illustration: _Fig. 74._]
[Illustration: _Fig. 75._]
[Illustration: _Fig. 76._]
[Illustration: _Fig. 77._]
[Illustration: _Fig. 78._]
[Illustration: _Fig. 79._]
=259.= True chucks are the most important adjuncts to a watchmaker’s
outfit. A true lathe with poor, untrue chucks is almost useless.
Chucks hold the work truest that comes the nearest to fitting the
holes in them. If you try to hold work in a chuck that is too large
or too small, you will soon get the chucks out of true and you will
soon become dissatisfied with your chucks, your work and your lathe.
Care should always be taken to select a chuck that will take the work
without straining it open and yet is not so large that undue pressure
will have to be used in holding it. The American split chuck, when
true, will hold almost any piece of work with the greatest precision as
regards truth; but the split chuck is a delicate attachment and will
not stand hard knocks and rough treatment. After using them, you should
clean them in benzine to remove all dirt, rinsing them in alcohol and
drying with a soft linen rag, and see that no small chips of metal are
left in the openings that may throw the work out of truth the next time
they are used. Fig. 74 illustrates the regular pattern split chucks
that accompany American lathes. Fig. 75 is a conoidal wire chuck, so
called because the shape of the mouth of the chuck is conoidal in
lieu of the shoulder usually left on wire chucks for the bend in the
spindle. Fig. 76 is an arbor chuck. This is a solid chuck on the end
of which is a threaded arbor for the reception of saws, laps, wheels,
etc., which are held firmly in position by means of the nut on the
threaded arbor. Fig. 77 is a screw chuck. This is a solid steel chuck
having a threaded hole in the end for the reception of cement brasses,
etc. Fig. 78 is a shoulder chuck. It is a split chuck with a large
opening in the end with square shoulders for the work to rest upon.
Fig. 79 is a taper chuck, which is solid and has a large opening for
the reception of tapers, centers, laps, etc. Fig. 80 is a step or wheel
chuck, which usually comes in sets of five, and as each chuck has
nine steps, a set of them will accommodate forty-five different sizes
of work. These chucks are useful for holding mainspring barrels when
fitting in the cap, should it become out of true; for trueing up the
barrel of English lever watches that are damaged by the breaking of a
mainspring and for holding almost any wheel in a watch, such as the
fitting of a center wheel to a pinion, or in making sure that hole in
the wheel is in the center. These chucks will the hold wheels from 5
to 2.25. The chucks mentioned above are the most common ones in every
day use and usually accompany the American lathe in combination sets.
As intimated, these chucks are delicate and as a usual thing they do
not receive the care they should, when their cost and the delicate
exactitude demanded of them is considered. The watchmaker who prides
himself on his good work and the orderly condition of his tools,
attachments and bench generally will purchase or make for himself a
nice chuck box with a glass or wooden cover to exclude all dust and
flying chips. You cannot expect to do good true work with a chuck that
is thrown carelessly into a drawer containing an assortment of files,
a hammer, staking block, oilstone, screw driver, sliding tongs, etc.,
and yet how many watchmakers take just this kind of care of their
chucks, and complain of their untruth, and declare that a wax chuck is
the only thing that can be absolutely relied upon for truth. Fig. 81
illustrates a neatly arranged chuck box made by the Faneuil Watch Tool
Company. In it all the various chucks may be arranged and the whole
may be covered with a glass shade to keep out all dirt. A wooden cover
might be used and perhaps would be preferable to many as it is less
liable to be broken and occupies less space and therefore admits of the
box being placed in a drawer, leaving more room on the bench for the
necessary tools and attachments.
[Illustration: _Fig. 80._]
[Illustration: _Fig. 81._]
A chuck box should be well soaked in oil so that the wood will absorb
no moisture and thus tend to rust the chucks. A small envelope made of
tissue paper and filled with quicklime will, if placed in the chuck
box, take up the moisture in the air and prevent the chucks from
rusting.
[Illustration: _Fig. 82._]
=260.= The chuck stepping device, invented and patented by Mr. Moseley,
is a valuable attachment for the lathe. In this device, shown in
Fig. 82, _a_ rests in chuck slightly less than diameter of work; _b_
tightens in rear end of draw-in spindle, and turning _c_ regulates the
depth of step. By the use of this tool any wire chuck will accurately
serve as a step chuck. It is a device of great service to the
watchmaker when used and understood. It enables him to make a step in
any wire chuck of any depth he may desire, and will push out the work
at any time when he so desires. It is very useful many times for a stop
for marking or cutting off when you want a number of pieces of the same
length or kind. Many object to the stepped chuck for general use.
[Illustration: _Fig. 83._]
=261.= In addition to the regular chucks which usually accompany
American lathe combinations may be mentioned some others which from
time to time have been placed upon the market by manufacturers of
watchmakers’ tools. These chucks were devised for holding work which it
was found in practice could not be held by the ordinary chucks.
=262.= The bezel chuck, shown in Fig. 83, was originally made with a
view of holding bezels only, but is now made so that it will hold watch
plates, coins, etc., and is adjustable to any size. It can be fitted to
any lathe and it requires but very little practice to use it, as it is
extremely simple and any one who uses a lathe can make or repair bezels
in a workmanlike manner. It holds the work as in a vise, and no amount
of turning or jarring will loosen the jaws, while it may be opened
or closed instantly by simply turning the milled nut behind the face
plate, thus enabling the operator to turn and fit a bezel perfectly, by
trying on the case as many times as necessary. It holds the bezel by
either groove, so that the recess may be turned out when too shallow or
too small for the glass, or the bezel may be inverted and turned down
when it rests too hard against the dial. It will be found especially
useful in turning out the inevitable lump of solder from the recess
of the bezel after soldering, and in fitting to case, as the process
of soldering generally makes the bezel shorter, and consequently it
will not fit the case. It also renders the operation of polishing
bezels, after soldering, the work of but a few moments. In turning out
the recess for glass in bezels, especially those of the heavy nickel
variety, it will prove a friend indeed. When, for instance, you look
through your stock of flat glasses and find none to fit, but have one
that is just too large. Any watchmaker knows that if the groove in the
bezel is imperfect, it is very apt to break the glass. This chuck is
also useful as a barrel closer, holding work while engraving, and many
other uses that will present themselves to the watchmaker.
[Illustration: _Fig. 84._]
=263.= The Hopkins’ patent adjustable chuck, shown in Fig. 84, is
designed to grip and hold firmly and accurately any size of work,
from the smallest staff to the largest pinion, watch wheels of all
sizes, mainspring barrels and other large work, and can be adjusted
to any make of lathe, by simply placing it friction tight on a plug
chuck fitted properly to the lathe. In using this chuck for staffs,
pinions, wire, etc., fasten a V-piece, 7, of proper size, in the hole
of attachment 6, taking care that both the V and the seat in which it
rests, are free from chips, dirt, etc. Then lay your work in the V and
fasten it there by means of the sliding jaw above it. This done, place
the attachment on the face of the chuck body, with the disc slipped
under the heads of the two spring bolts, and then spin the work to
center the same as when using wax. After centering thus, fasten the
disc to place by tightening the nuts on the back ends of the spring
bolts. For holding work by the web of the wheel, place the wheel under
the screw cap, on the face attachment 8, and screw the cap down firmly
on it, with the staff or pinion projecting outward through the center
hole. This done, proceed the same as when using attachment 6. For
mainspring barrels and like work, use attachment 11, and place a bit
of broken mainspring between the work and the ends of the three binding
screws, and tighten the screws down on this instead of directly on the
work.
[Illustration: _Fig. 85._]
[Illustration: _Fig. 86._]
=264.= The Spickerman patent cement chuck, shown in Figs. 85 and 86,
holds and centers accurately any wheel in a watch while drilling,
polishing or fitting new staffs or pinions, and all danger of injuring
the wheels is obviated. It will fit all kinds of American or Swiss
lathes. The holder shown in Fig. 86 at _a_, is turned down to nearly
the size of the screw for the lathe, and the screw is cut so the holder
will set as close as possible to the lathe. The face of the holder is
then turned perfectly true. Put the wheel to be centered in cap _c_, as
near to the center as convenient, and then screw on _b_. Then place the
cemented face of chuck _b_ against the face of holder _a_ on the lathe,
and with a lamp warm the cement between the surfaces, holding the chuck
by means of a pegwood against the pivot of the wheel in the cap _c_,
and it will move to an exact center as soon as warmed sufficiently. New
cement should be added occasionally between the surfaces, as the old
cement hardens and burns away, and does not center as well as when new.
Fig. 85 shows chuck with wheel inside ready for centering and drilling.
[Illustration: _Fig. 87._]
[Illustration: _Fig. 88._]
=265.= The gem patent pivoting chuck, shown in Figs. 87 and 88, is
intended as a substitute for wax when performing pivoting and like
work. By the means of the ball _b_, placed between the two sliding
sockets _c_, _c_, with the several other parts as represented in
Fig. 87, a combination of sliding and ball and socket movements, in
connection with a spring pump-center is obtained. A set of ten or more
supplementary chucks _g_, with different sizes of center holes, and
attachment _n_ for all sizes of wheels, are furnished with each chuck.
The supplementary chuck _g_, in the form of a small split chuck, is
made to fit into a hole with taper mouth, in the center of the ball
_b_, and is drawn into place and the work fastened firmly in it by
means of the binding nut _m_, which screws on to a projection extending
outward from the front of the ball. To use this chuck, proceed as
follows: Remove the nut _m_, and give freedom to the working parts by
loosening the large back nut _k_. Then to bring the hole through the
ball _b_ into line, spin the ball to center, first at the base of the
projecting screw and then at the mouth of the hole through it, and in
this position again fasten the parts, by tightening the nut _k_. Then
give freedom to the pump-center by slightly loosening the set screw
_j_. When doing this, hold your finger against the front of the chuck,
to prevent the center rod from shooting out of its place when freed.
Then having placed a supplementary chuck _g_, of proper size, in its
place in the chuck, and your work in it, with its back end resting
properly in the countersink in the end of the pump-center, fasten it
there by screwing the cap _m_ down snugly over it, using a small lever
pin when necessary for the purpose, but not with undue force. Then
again loosen the nut _k_, and spin the work to center at its outer end;
and then tighten both the nut _k_ and set screw _j_. In tightening
the set screw _j_, make sure it is so tightened as to prevent the
pump-center from slipping from place when working. If from tightening
the screw _j_, it is found that the work has been thrown in any degree
away from true center, loosen the nut _k_, leaving the pump-center
fast, and again spin to center and fasten as before. After a little
practice this can all be done in a few seconds, and the work brought to
absolute center.
In using attachment _n_, for wheels, the nut _m_ and chuck _g_ are
removed, and n is substituted therefor; the work being held on the
face of the attachment by flat-headed screws that grip the arms of the
wheel. For cylinder escape wheels a special attachment _n_ is furnished.
[Illustration: _Fig. 89._]
[Illustration: _Fig. 90._]
=266.= Fig. 89 illustrates a crown chuck, which is used for holding
crowns while undergoing repairs. The Dale chuck shown in Fig. 89
is made on the lines of the ordinary split wire chuck, a large
recess being turned in the end for the reception of the crown. The
Johanson chuck is illustrated in Fig. 90, and is quite different in
construction, a ball-shaped cap with right hand thread screwing down
onto the body of the chuck, thus holding the crown from the outside,
while a screw-center with left hand thread, holds it firmly from the
inside. This chuck is made in two patterns, one for use in a No. 40
wire chuck, as shown in Fig. 90, and the other is mounted on a regular
chuck and is ready to insert into the lathe-head the same as an
ordinary wire chuck.
THE SLIDE REST.
[Illustration: _Fig. 91._]
=267.= The slide rest is an expensive but very useful adjunct to the
lathe. It is used so extensively in this country, however, that a full
description of it seems superfluous. Fig. 91 is a fair example of a
modern slide rest for the American lathe. The tool-holder varies with
the different makers, but the rests proper are all made on the same
general principles, that of two sliding beds working at right angles
to each other, and carrying a tool-holder, capable of being raised or
lowered or set at any desired angle.
=268.= Brass is easily turned with the slide-rest in an ordinary lathe
arranged for the purpose, but the turning of steel demands more care in
setting the cutter so as to obtain the best cutting edge as well as in
determining the point of application of the tool. Preliminary trials
must be made, and the following remarks will be of service as a guide.
[Illustration: _Fig. 92._]
=269.= Engineers use a hooked tool to a very great extent for both
planing and turning. Both experience and reasoning point to the
conclusion that a tool of the form _b_ or _d_ Fig. 92, possesses many
recommendations, and numerous designs of hooked tools more or less
resembling these figures are employed with advantage; the tool occupies
the best possible position in reference to the surface it is required
to cut, and the cutting edge is both sharp and solid. It will be
evident that a certain relation exists between the cutting angle and
the point of application of the tool to the cylindrical object that
is being turned, and this it is necessary to determine. With a hooked
tool, as with the ordinary slide-rest cutter, a cutting angle which is
too acute will wear away rapidly; when too obtuse, the tool scrapes and
will only act when considerable pressure is applied.
In conclusion, it is clear that in forming or re-grinding any tool for
cutting a surface, it must be so arranged that its edge makes the least
possible angle with the surface that is consistent with the securing
of a sufficient degree of resistance to the cohesion and the hardness
of metal operated upon; in other words, the end of the tool must be
almost tangential to the circumference of the object, and the angle of
the cutting edge must be obtained by removing metal from the top face
of the tool. These principles are applicable to all tools for metals;
to the blades of drills as well as to the cutting edges of gravers, etc.
=270.= The angle of the cutting edge of the tool used in the slide rest
for steel should be less than that employed for operating on brass.
According to Holtzapffel, it may vary in the former case from 60° to
80° and, in the latter case, 70° to 90°, according as the tool is
required for rough turning or finishing. 60° and 80° may, however, be
taken as convenient angles in the cases respectively. Simple methods of
ensuring that the cutting edge has any required angle are described in
article 396.
The velocity with which the lathe revolves should also be less when
turning steel, and care must be taken that both the tool and object are
constantly moistened with oil.
It is sometimes desirable to arrange a small dropping-can for the
purpose of keeping up the supply; this may be easily done by placing
a can containing the fluid above the level of the work and allowing
a piece of lamp-wick, previously moistened, to hang from it so as to
almost touch the work: a continuous series of drops will fall, owing to
the influence of capillarity.
[Illustration: _Fig. 93._]
=271.= When roughing out work it is best that the cutter first travel
perpendicular to the object, from _a_ towards _b_, Fig. 93, and then
in the direction of the arrow. The corner _a_ should only be used for
finishing an internal angle or for roughing it out, and, in this latter
case, the cutter must advance along _a b_ and be withdrawn from the
metal in the direction of the arrow. The small face at the end, _a c_,
should be narrow.
[Illustration: _Fig. 94._]
=272.= =Forms of slide-rest cutters.= The usual forms of cutters
for use in the slide-rest are shown in Figs. 94 and 95. A and A′
are respectively the plan and side view of the most common form.
Two inclined planes _i n_ and _d c_ are formed on the left-hand and
under sides. The point on which they terminate is cut off square, a
cutting edge, which is more or less acute according to the metal to be
operated upon, being obtained by a third incline _c n_. The width of
the square cutting edge, indicated at _n_ in figure A, varies according
to the metal to be operated upon, as well as this incline _c n_. It is
advisable to be provided with at least half-a-dozen cutters of this
form, with edges of varying width and inclination, and even this number
is often found insufficient; cutters for steel should never be used in
turning brass.
[Illustration: _Fig. 95._]
A cutter may be sharpened in the usual manner for ordinary work; but
if it is desired to produce very smooth sinks, etc., one that has been
carefully polished must be used for the final cut.
The blade should cut with both its edges; the straight edge will serve
to form right-angled corners of sinks, while the other edge will form
bevels. It is hardly necessary to add that, when a square corner formed
by the first of these edges requires to be beveled by the second, the
lathe must rotate in the opposite direction and the cutter be passed
over to the opposite side of the center.
=273.= C, in the same figure, is a rounded cutter for making circular
grooves. F, Fig. 95, is for cutting the groove that receives a
barrel-cover. J and V are for forming the “tallow-drop” shoulders of
pivot-holes, etc.
It will doubtless be observed that these cutters would form nipples
that are dome-shaped and relatively somewhat high, and, for small
pivot-holes, the blade would require to be narrower and of a shape that
corresponds with the nipple it is desired to produce. L is for rounding
off angles. S is a convenient shape for smoothing the bottom of a
barrel without damage to the hook. T has a square point; it is used
narrow for cutting, for example, the passage under the escape-wheel
cock in a cylinder watch, and, when made wider, will serve to cut the
settings for jewels. In the latter case it may either be square at the
end or a little rounded at the corners.
In addition to the use indicated above, V can be employed for raising
the edge of a jewel setting.
=274.= =Sharpening slide-rest tools.= A flat surface turned in the
lathe will never be even unless the cutting face _n_ in A Fig. 94, is
smooth, and indeed polished, and its edge parallel to the face-plate.
Some care is therefore necessary in sharpening this face. The requisite
parallelism can be secured by the following method.
=275.= Sharpen the tool while it is held in the tool represented in
Fig. 96.
[Illustration: _Fig. 96._]
On a thick brass plate _l_ and parallel to its plane at one extremity
_b_, a plate _p_ is pivoted. The inclination of _p_ to _l_ can be
varied and it is fixed in any required position by the curved arc
passing under the clamping screw _j_.
A small bar _c_ is fixed to _l_ with its edge set accurately at right
angles to the line at _b′_ in which the two planes intersect. An
examination of the figure will suffice to indicate the manner in which
such a tool is used. Having set _p_ so that it makes with _l_ the angle
to be given to the cutting face, the cutter _b_ is held against the
bar _c_, where it may be fixed with a screw _v_, or in any convenient
manner, taking care to leave the portion of the cutter that is to be
removed projecting beyond the face of _p_ as shown at _b′_. Now pass
a piece of smooth oilstone or disc of steel charged with oilstone
dust over the face of _p_ until the projecting portion is removed; if
a polished face is required, this must be succeeded by a bronze or
ground glass disc charged with rouge. If the plate _p_ is of sufficient
dimensions, it will not be distorted, even though only made of hammered
brass; but it would of course be better made of steel, hardened if
possible.
=276.= If the watchmaker will make a rectangular holder to fit in his
tool post, with a square groove planed in its upper side that will fit
some particular size of tool steel, say one-fourth or three-sixteenths
of an inch, he can then buy bar steel of that size and make his cutters
by simply cutting off a piece from the bar and grinding one end to the
desired shapes and angles, thus saving a vast amount of time and labor
in the preparation of his tools, facilitating their rapid interchange
in the tool post, when working, and securing the greatest possible
rigidity of the tool, as the cutting edge projects from the holder only
far enough to allow the holder to clear the work.
GRAVERS AND OTHER HAND-TURNING TOOLS.
=277.= =Hooked gravers.= It is needless to do more than mention the
gravers that some watchmakers are in the habit of making of worn-out
files, of various forms to suit their special requirements; but we
would remind learners that care is essential in fixing the position of
the rest and the inclination that has to be given to the tool so as to
obtain a smooth surface, and at the same time a rapid removal of metal.
The most usual forms of the hooked graver are shown in Fig. 97. A will
serve to hollow out a plate, barrel, etc.; B for turning the bottom of
a barrel without touching the hook; C for forming a barrel-cover groove
after it has been roughed out with an ordinary graver. The bottom of
a barrel can also be turned with a graver of the form D held on the
=T=-rest at right angles to the bottom, and a slide-rest cutter can be
made of this form with advantage.
[Illustration: _Fig. 97._]
Some workmen incline the end cutting face of A slightly backwards from
the perpendicular to _d d_, fearing lest, in sharpening, it should
accidentally be made to incline in the other direction, and so make it
difficult to form internal square corners.
=278.= =Gravers for turning square shoulders, etc.= Very few
watchmakers are able to finish off a square shoulder by using a graver
with the usual point; as a rule, when they are smoothing the surface
of the pivot they allow the point to cut a ring in the shoulder, and
if, instead of being sharp, the point is dull, a rough groove is the
result.
To avoid such a fault it is a common practice to employ gravers with
very short faces, but their inconvenience is evident. It is much better
to retain the long lozenge-shaped face, but with the point modified, as
indicated by B or C, Fig. 98.
The ordinary point, shown at A, can be used for cutting the back
slope of a shoulder, B for forming the square-shouldered pivot, and
C for beveled shoulders. The inclination of the face _e d_ of B may
vary, the angle _e_ being more or less acute, according as more or
less use is required to be made of the point. This form of graver has
the double advantage that a pivot can be turned and smoothed at one
operation, very little polishing being needed. Moreover, the point is
less fragile, and such a graver combines the advantages of those with
pointed and square ends.
[Illustration: _Fig. 98._]
The length of this small face depends on the work required of it, thus
for making a cylinder pivot it may be about a third the length of the
pivot; this is found convenient for ensuring that the pivot shall be of
uniform diameter. The direction to be given to the face is indicated
by the dotted line _e d_, and a lozenge-shaped graver is preferable to
one of square section for this purpose. This direction _e d_ is very
important, and frequent trials should be made so as to ensure its being
always produced. The form C for beveling off a shoulder does not call
for explanation.
Although of less importance than when turning with the slide-rest, the
cutting angle of the graver should correspond with the nature of the
metal operated on. In reference to this question see article =270=.
=279.= =Spherical turning tool.= A very simple and convenient tool for
forming a sphere of metal may be made by taking a hardened steel tube
whose internal diameter is less than that of the sphere to be produced.
This is ground square and flat at one end, and sharpened by rubbing
this flat end on an oilstone. The tool is moved about over the surface
of the ball, previously roughed out, and a perfect sphere will soon be
obtained, the metal being removed by the internal edge of the tube. If
a steel tube is not accessible it will be enough to drill a hole in the
end of a softened worn-out file, subsequently hardening it.
DRILLS.
[Illustration: _Fig. 99._]
=280.= The forms ordinarily adopted for the blades of drills are shows
at A and C, Fig. 99. The form C is best suited for perforating brass
and other metals having a similar degree of hardness. The blade must
not be too thick, as, if it were, there would not be a sufficient
cutting edge. As the hardness of the metal operated on is greater, the
thickness of the blade must proportionately increase, or what amounts
to the same, the two slopes that give the cutting edges must have a
less degree of inclination. If this condition of sufficient thickness
be satisfied by a drill of the form C, it will perforate steel very
well, but its point will rapidly wear. When operating on this metal,
therefore, the form A is preferable, especially when the steel is at
all hard. Such a drill with the corners rounded off and sharpened will
last for a long time, if the cutting angles are not too acute. If the
metal is not hard, more rapid progress may be made by adopting a blade
less flattened than A, that is to say, something intermediate between A
and C.
A drill may be asserted to be good if it satisfies the following
conditions: the point must be in the middle of the blade; it must be
made of good steel that is carefully hardened, without being heated
beyond the proper temperature; lastly, it must be quite true—in other
words, in rotating it must run with sufficient truth throughout its
entire length, so that it withstands the end pressure required to cause
it to bite, and does not bend.
=281.= It must not be forgotten that: (1) if a drill is driven too
rapidly it will heat, and thus become softened as though too much
tempered; it is with a view to prevent this that, when operating upon
iron or steel, many workmen now and then dip the drill into a cold
liquid (turpentine is good for this purpose), dry it, and recommence
drilling, the hole being liberally supplied with oil; (2) when the
blade is left too hard, the cutting edge too acute, or if a feather
edge has been left by the oilstone, small hard particles that are
detached from the drill will embed themselves in the hole, and this
will be especially the case if it is worked too rapidly or with jerks;
such particles render the operation of drilling very slow and difficult.
=282.= =To drill steel of a blue temper.= At first not much difficulty
will be experienced; but when the drill reaches a certain depth and the
metal seems to oppose a gradually increasing resistance, the operation
must at once be stopped. If the blade of the drill be now examined
with a glass, it will be easy to see which points have ceased to cut,
producing instead a series of bright rings at the bottom of the hole
that are very difficult to remove. Exchange the drill for one of a
different form or, without reducing its width, change the form of the
blade; if it was arrow-headed for example, make it a semicircle, or
semi-oval, or chisel-shaped with sloping edges. All that is essential
is that the form be so changed that the bright portions of the surface
shall be gradually removed, and that no attempt be made to act on the
whole bright surface at once. Until this hard portion is removed, the
blade will require frequent sharpening.
Some authorities recommend that the hole be moistened from time to time
with dilute nitric acid, which is then washed off, and renewed when
a shiny surface is produced. Oil can with advantage be replaced by
turpentine as a lubricant for the drill blade.
The formation of hard shining surfaces is attributed to three causes:
(1) to the cutting edge being rounded, rolling as it were and hardening
the surface of the metal against which it continues to move; (2) to the
drill being made of bad steel or imperfectly hardened, so that small
particles break off and are embedded in the metal operated upon; and
(3) to a deficiency in the supply of oil, or an excessive velocity of
rotation of the drill.
These difficulties may usually be avoided by observing the following
precautions:
[Illustration: _Fig. 100._]
=283.= _Blade of the drill._ This should be neither as thin nor as
acute as is used for drilling brass. Its angle should never be less
than 100° and the incline should be at about 45°. The forms generally
employed are shown in Fig. 100, at A, B and C. At first the form A is
used, and, as the operation progresses, it is modified with an oilstone
slip.
=284.= _Drilling slowly with considerable pressure._ If the drill
rotates too rapidly or there is not sufficient oil, the surfaces of
contact will be heated and shining rings will form. It is well to
practice slightly, varying the speed of the wheel, in accordance
with the pressure applied; the speed should be more decided when the
pressure is, for the instant comparatively great. With continuous
rotation, considerable pressure should be applied with moderate
velocity. Constantly remove the drill to sharpen, clean the hole and
have an abundant supply of oil. Whatever liquid is most effective in
maintaining the drill cool will probably be the best; turpentine is
better than oil, since it has the additional advantage of increasing
the “bite” of the drill.
=285.= _The part against which the drill acts should be very rigid._
For example, if a hole is being made for a pivot in a cylinder plug
which is not provided with a shellac backing, and is, therefore,
flexible, the operation will be more tedious than when the cylinder is
filled with shellac. The firmness is usually greater when the object is
centered about the point to which the drill is applied.
=286.= _Making the drill._ The very best steel should be used, and the
precautions indicated in article =87= should be taken in the hardening.
If the steel is burnt in this process, no satisfactory results are to
be expected of it. To avoid such a danger it is often advisable to
leave the blade nearly round and thicker than is required, finishing
with a piece of oilstone. Although somewhat more tedious, this method
has the advantage of ensuring that, after hardening, all the metal
that is most liable to have been burnt is removed.
The drill must be short, the blade being thick and not much reduced at
the shoulder, in order to stand pressure when in use. A drill that has
been several times hardened is rarely good.
=287.= =Finished drills.= We would here draw the attention of
watchmakers to some beautifully made drills that have been introduced
and are known in the trade as “finished” drills, in contra-distinction
to the well known pivot drills that are always sold in the rough. They
are of two forms, corresponding to A and C, Fig. 99, for steel and
brass respectively; they are made of the best steel, carefully hardened
and tempered to the requisite degree; and a principal recommendation
consists in the fact that, while being moderate in price, they are of
definite graduated sizes, extending from 0.1 mm. to 2.5 mm. (0.004 to
0.1 inch), a range which comprises 37 distinct sizes.
=288.= =Semi-cylindrical drills.= These drills give excellent results
when driven by a wheel, and, although they have been long in use by
engineers, they are hardly known to watchmakers.
[Illustration: _Fig. 101._]
The simplest form is a cylindrical rod rounded at its end and then
filed down to a trifle less than half its thickness, as seen at _b d_
and _l i_, Fig. 101.
The length of the point is greater or less according to the nature of
the metal to be operated upon, but under no circumstances must the
point itself be sharp. With the form shown at _b d_, some of the rod
that is left cylindrical must be partially filed away; a better shape
is indicated by the dotted lines, all the metal being removed that
is outside the line _i l_. With such a drill the hole is smoothed
immediately after it is made by one or the other cutting edge of the
portion _i l_. It should be sharpened on the round, not on the flat
surface (or at any rate very slightly), because the thickness would
be rapidly reduced and the blade made smaller. When such a drill does
not turn true the back of the blade can be reduced, starting from the
cutting edge, it being observed that, with the continuous motion of the
wheel, only one edge acts. After a few trials it will be found easy to
use this form of drill.
It possesses this very great advantage: when fixed in a drill-chuck,
it can be turned exactly round, of the required diameter and finished;
so that, whenever replaced in the chuck, one can be certain beforehand
that the hole drilled will be of a definite diameter.
[Illustration: _Fig. 102._]
=289.= Fig. 102, shows, at C and D, another form of semi-cylindrical
drill; the first, C, is a front and the second a side view. The angle
_a_ is formed by a sloping semicircle and the stem of the drill is of
less diameter than the head, as indicated by the shoulder _j_. The
angle _t s r_ and the one between the face D and the plane _b a_ must
not be too acute.
This drill works evenly, but two conditions must be satisfied; it must
be maintained perfectly true by the chuck, and, in commencing, both
sides of the blade must engage against the sides of a conical opening
that forms the beginning of a hole which has to be enlarged.
[Illustration: _Fig. 103._]
=290.= At F and N M, Fig. 103, are seen front and side views of
another form of drill. While acting in a similar manner to the others
described above, it differs from them in that the blade also cuts with
its two sides; the edges, _p_, _i_, _i_, _o_, are sloped off backwards
to form cutting angles. The shape is indicated to the right of M, this
portion being the exact inverse of the side N.
As with the drills previously considered, a few trials must be made to
decide upon the best slopes for the cutting angles, etc., according to
the metal operated upon. They may be retained as left by the lathe, or
very slightly inclined, on the faces _p_ and _i_. All these forms of
drills require to be mounted so as to run very true. The point _o_ must
be accurately central. A hole that has been already drilled small can
be rapidly enlarged by such a drill as this last, the pin _o_, having
the same diameter as the one originally drilled.
[Illustration: _Fig. 104._]
=291.= =The Twist Drill.= The Morse twist drill, shown in Fig. 104, is
rapidly coming into favor with watchmakers for the heavier classes of
work, and is very desirable when drilling deeply, as this form of drill
heats slowly and the particles are carried to the surface of the work.
A large range of sizes in these drills are now carried in stock by the
material dealers.
LATHE ATTACHMENTS.
=292.= =Tailstocks.= Besides the regular tailstock which accompanies
the American lathe there are several other varieties made for use on
special kinds of work. Fig. 105 illustrates the half open tailstock
which is cut away so that the spindles can be laid in, instead of
being passed through the holes. The fixture will be found exceedingly
convenient when several spindles are to be used for drilling,
counterboring and chamfering. Fig. 106 illustrates the screw tailstock,
an attachment which is very convenient for all kinds of heavy drilling,
the spindle being moved by a screw with hand-wheel attached. Fig. 107
illustrates the traverse spindle tailstock, which will be found very
convenient for straight drilling and especially where the watchmaker
has considerable drilling to do.
[Illustration: _Fig. 105._]
[Illustration: _Fig. 106._]
[Illustration: _Fig. 107._]
[Illustration: _Fig. 108._]
=293.= =Jeweling Caliper Rest.= Although this tool was invented and
manufactured for the purpose of cutting jewel settings it may be used
to great advantage in countersinking for screw heads, opening wheels
for pinions or bushings, etc. The sliding jaws of the calipers should
be so adjusted that when the swinging part is brought back snugly
against them, the front cutting edge of the cutter in the sliding
spindle will exactly line with the center of the lathe spindle. Then
if the calipers are at the right height, when a jewel or jewel setting
is placed in the jaws of the caliper it will move the edge of the
cutter outward from the lathe center just half the diameter of the
jewel then in the caliper and the cutting made at that distance from
the center will exactly coincide with the size of the jewel to be set.
If however, when set and worked as above, it is found that the hole
cut is too large for the jewel, it will indicate that the calipers are
too low down and should be raised, provision for which is made in the
construction of the tool. Upon the other hand, if the cutting is found
too small to fit, it will indicate the calipers should be lowered. The
final cutting for the jewel seat should be made by running the center
straight inward from the face of the plate; the adjustable stop screw
on the back end of the sliding spindle, serving to gauge the depth of
the cutting.
[Illustration: _Fig. 109._]
[Illustration: _Fig. 110._]
[Illustration: _Fig. 111._]
[Illustration: _Fig. 112._]
=294.= =Pivot Polishers.= The pivot polisher is used for grinding
and polishing conical and straight pivots and shoulders. It is also
used for drilling, polishing or snailing steel wheels, milling out
odd places in plate or bridge, where only a part of a circle is to be
removed, etc. In the style shown in Fig. 109, the American Watch Tool
Co.’s polisher, and Fig. 110, the Moseley pattern, the circular base
is graduated to degrees and the fixture can be set at any angle. The
spindle has a taper hole for drill chucks, which makes the fixture very
useful for drilling either in the center or eccentric and by using the
graduations on the pulley of the headstock an accurately spaced circle
of holes may be drilled. Fig. 111 illustrates the polisher made by the
Faneuil Watch Tool Company, and is intended to be mounted on the slide
rest. Fig. 112 illustrates the Johanson pivot polisher and in general
principle is like the others. This style is made both for use on the
slide rest and also for the hand rest. When used in the latter, a
stud, shown in Fig. 113, is screwed into the base plate and supports
the tool in the hand rest, so as to be readily adjustable in any
direction. When used in the slide rest, this stud is removed and the
plate clamped between two hollow cylindrical supports by a stud which
is slipped into the groove of the slide rest and fasted by a nut at the
top, the whole forming a turret-like mount of great strength and upon
which the machine can be readily swiveled in any direction. In general,
polishers are used as follows: After the pivot is turned to proper
shape, put on your polisher, with the lap back of the pivot, usually
the cast iron lap first. A square-cornered lap for square shoulders and
a round-cornered lap for conical pivots. The laps for conical pivots
can be readily cornered with a fine file, and cross-ground with fine
oilstone to remove any lines made by graver or files. Lines on the end
can be removed the same way, or by means of the fingers often rubbing
them on a piece of ground glass which has on it a paste of oilstone
powder and oil, well mixed. Oilstone powder and oil used on the lap,
or No. 1 crocus will rough out the work well. When roughed out to your
liking, wipe off the oilstone powder or crocus and with a little oil
touch the pivot gently; repeat the second time. Then change lap for one
of boxwood or brass and use crocus No. 4, very fine, and ground down
to a paste. Proceed as with the first lap, being careful at all times
to keep the lap properly oiled and not pressed too hard against the
work, particularly in the last operation. Be sparing of your grinding
and polishing material as a little will accomplish as much work as a
large quantity and do it better. Bring the lap up carefully against the
work until spread all the way around, then proceed, bearing in mind
that grinding is not polishing, and that to polish nicely the work
and lap must be very nearly the same shape. Fig. 114 illustrates the
Hardinge pivot polisher, which is a hand polisher and much more simple
in construction and use than those mentioned above. It is attached to
the lathe bed the same as the T or hand rest. Polishing and grinding
slips are furnished with this attachment, as with the others.
[Illustration: _Fig. 113._]
[Illustration: _Fig. 114._]
=295.= =Centering Attachments or Back Rests.= These attachments are
very useful in rapidly bringing work to an accurate center, when
pivoting, staffing, etc., and particularly where a large number of
pieces have to be centered successively. Fig. 115 illustrates the
Potter patent self-centering lathe attachment which is made to fit any
pattern of American lathe.
[Illustration: _Fig. 115._]