objects on heating to redness: Mix 1 part of white soap, 6 parts of
chemically pure boracic acid, and 4 parts of phosphate of soda, after
pulverizing, and make with water into a paste. For use, apply this to
the article before the annealing.
«COLORING STEEL:»
«Black.»—I.—Oil or wax may be employed on hard steel tools; with both
methods the tool loses more or less of its hardness and the blacking
process therefore is suited only for tools which are used for working
wood or at least need not be very hard, at any rate not for tools which
are employed for working steel or cast iron. The handsomest glossy
black color is obtained by first polishing the tool neatly again after
it as been hardened in water, next causing it to assume on a grate or
a hot plate the necessary tempering color, yellow, violet blue, etc.,
then dipping it in molten, not too hot, yellow wax and burning off the
adhering wax, after withdrawal, at a fire, without, however, further
heating the tool. Finally dip the tool again into the wax and repeat
the burning off at the flame until the shade is a nice lustrous black,
whereupon the tool may be cooled off in water. The wax is supposed to
impart greater toughness to the tool. It is advisable for all tools
to have a trough of fat ready, which has been heated to the necessary
tempering degree, and the tools after hardening in water are suspended
in the fat until they have acquired the temperature of the fat bath.
When the parts are taken out and slowly allowed to cool, they will be a
nice, but not lustrous, black.
II.—The following has been suggested for either steel or iron:
Bismuth chloride 1 part
Mercury bichloride 2 parts
Copper chloride 1 part
Hydrochloric acid 6 parts
Alcohol 5 parts
Water sufficient to make 64 parts.
Mix. As in all such processes a great deal depends upon having the
article to be treated absolutely clean and free from grease. Unless
this is the case uniform results are impossible. The liquid may be
applied with a swab, or a brush, but if the object is small enough to
dip into the liquid better results may thus be obtained than in any
other way. The covering thus put on is said to be very lasting, and a
sure protection against oxidation.
«Blue.»—I.—Heat an iron bar to redness and lay it on a receptacle
filled with water. On this bar place the objects to be blued, with the
polished side up. As soon as the article has acquired the desired color
cause it to fall quickly into the water. The pieces to be blued must
always previously be polished with pumice stone or fine emery.
II.—For screws: Take an old watch barrel and drill as many holes into
the head of it as the number of screws to be blued. Fill it about
one-fourth full of brass or iron filings, put in the head, and then fit
a wire long enough to bend over for a handle, into the arbor holes—head
of the barrel upward. Brighten the heads of the screws, set them, point
downward, into the holes already drilled, and expose the bottom of the
barrel to the lamp, until the screws assume the color you wish.
III.—To blue gun-barrels, etc., dissolve 2 parts of crystallized
chloride of iron; 2 parts solid chloride of antimony; 1 part gallic
acid in 4 or 5 parts of water; apply with a small sponge, and let dry
in the air. Repeat this two or three times, then wash with water, and
dry. Rub with boiled linseed oil to deepen the shade. Repeat this until
satisfied with the result.
IV.—The bluing of gun barrels is effected by heating evenly in a muffle
until the desired blue color is raised, the barrel being first made
clean and bright with emery cloth, leaving no marks of grease or dirt
upon the metal when the bluing takes place, and then allow to cool in
the air. It requires considerable experience to obtain an even clear
blue.
«Brown.»—I.—The following recipe for browning is from the United States
Ordnance Manual: Spirits of wine, 1 1/2 {683} ounces; tincture of
iron, 1 1/2 ounces; corrosive sublimate, 1 1/2 ounces; sweet
spirits of niter, 1 1/2 ounces; blue vitriol, 1 ounce; nitric acid,
3/4 ounce. Mix and dissolve in 1 quart of warm water and keep in a
glass jar. Clean the barrel well with caustic soda water to remove
grease or oil. Then clean the surface of all stains and marks with
emery paper or cloth, so as to produce an even, bright surface for the
acid to act upon, and one without finger marks. Stop the bore and vent
with wooden plugs. Then apply the mixture to every part with a sponge
or rag, and expose to the air for 24 hours, when the loose rust should
be rubbed off with a steel scratch brush. Use the mixture and the
scratch brush twice, and more if necessary, and finally wash in boiling
water, dry quickly, and wipe with linseed oil or varnish with shellac.
II.—Apply four coats of the following solution, allowing each several
hours to dry. Brush after each coat if necessary. After the last coat
is dry, rub down hard.
Sulphate of copper 1 ounce
Sweet spirits of niter 1 ounce
Distilled water 1 pint
«Niello.»—This is a brightly polished metal, which is provided with a
black or blue-black foundation by heating, is covered with a design by
the use of a suitable matrix and then treated with hydrochloric acid
in such a manner that only the black ground is attacked, the metal
underneath remaining untouched. Next, the acid is rinsed off and the
reserve is removed with suitable solvents. The parts of the metal bared
by the acid may also be provided with a galvanic coating of silver or
other metal.
Another method is to plunge the articles for a few minutes into a
solution of oxalic acid and to clean them by passing them through
alcohol. In this way the polish can even be brought back without the
use of rouge or diamantine.
«Whitening or Blanching.»—If dissatisfied with the color acquired
in tempering, dip the article into an acid bath, which whitens it,
after which the bluing operation is repeated. This method is of great
service, but it is important to remember always thoroughly to wash
after the use of acid and then allow the object to remain for a few
minutes in alcohol. Sulphuric acid does not whiten well, often leaving
dark shades on the surface. Hydrochloric acid gives better results.
Small pieces of steel are also whitened with a piece of pith moistened
with dilute sulphuric acid, else the fine steel work, such as a watch
hand, is fixed with lacquer on a plate and whitened by means of pith
and polishing rouge, or a small stiff brush is charged with the same
material. It is then detached by heating and cleaned in hot alcohol.
«TEMPERING STEEL.»
The best temperature at which to quench in the tempering of tool steel
is the one just above the transformation point of the steel, and this
temperature may be accurately determined in the following manner,
without the use of a pyrometer. The pieces of steel are introduced
successively at equal intervals of time into a muffle heated to a
temperature a little above the transformation point of the steel. If,
after a certain time, the pieces be taken out in the reverse order they
will at first show progressively increasing degrees of brightness,
these pieces being at the transformation point. When this point is
passed the pieces again rapidly acquire a brightness superior to that
of their neighbors, and should then be immediately quenched.
I.—Heat red hot and dip in an unguent made of mercury and the fat of
bacon. This produces a remarkable degree of hardness and the steel
preserves its tenacity and an elasticity which cannot be obtained by
other means.
II.—Heat to the red white and thrust quickly into a stick of sealing
wax. Leave it a second, and then change it to another place, and
so continue until the metal is too cool to penetrate the wax. To
pierce with drills hardened in this way, moisten them with essence of
turpentine.
«To Temper Small Coil Springs and Tools.»—To temper small coil springs
in a furnace burning wood the springs are exposed to the heat of the
flame and are quenched in a composition of the following preparation:
To a barrel of fish oil, 10 quarts of rosin and 12 quarts of tallow are
added. If the springs tempered in this mixture break, more tallow is
added, but if the break indicates brittleness of the steel rather than
excessive hardness, a ball of yellow beeswax about 6 inches in diameter
is added. The springs are drawn to a reddish purple by being placed on
a frame having horizontally radiating arms like a star which is mounted
on the end of a vertical rod. The springs are laid on the star and are
lowered into a pot of melted lead, being held there for such time as is
required to draw to the desired color.
It is well known that the addition of {684} certain soluble substances
powerfully affects the action of tempering water. This action is
strengthened if the heat-conducting power of the water is raised by
means of these substances; it is retarded if this power is reduced,
or the boiling point substantially lowered. The substance most
frequently used for the purpose of increasing the heat-conducting
power of tempering water is common salt. This is dissolved in varying
proportions of weight, a saturated solution being generally used as a
quenching mixture. The use of this solution is always advisable when
tools of complicated shape, for which a considerable degree of hardness
is necessary, are to be tempered in large quantities or in frequent
succession. In using these cooling fluids, care must be taken that a
sufficient quantity is added to the water to prevent any great rise of
temperature when the tempering process is protracted. For this reason
the largest possible vessels should be used, wide and shallow, rather
than narrow and deep, vessels being selected. Carbonate of soda and
sal ammoniac do not increase the tempering action to the same extent
as common salt, and are therefore not so frequently employed, though
they form excellent additions to tempering water in certain cases.
Tools of very complicated construction, such as fraises, where the
danger of fracture of superficial parts has always to be kept in view,
can with advantage be tempered in a solution of soda or sal ammoniac.
Acids increase the action of tempering water considerably, and to a far
greater extent than common salt. They are added in quantities up to 2
per cent, and frequently in combination with salts. Organic acids (e.
g., acetic or citric) have a milder action than mineral acids (e. g.,
hydrochloric, nitric, or sulphuric). Acidulous water is employed in
tempering tools for which the utmost degree of hardness is necessary,
such as instruments for cutting exceptionally hard objects, or when
a sufficiently hard surface has to be given to a kind of steel not
capable of much hardening. Alcohol lowers the boiling point of water,
and causes so vigorous an evaporation when the water comes in contact
with the red-hot metal, that the tempering is greatly retarded (in
proportion to the amount of alcohol in the mixture). Water containing
a large quantity of alcohol will not temper. Soap and soap suds will
not temper steel; this property is made use of in the rapid cooling
of steel for which a great degree of hardness is not desirable. When
certain parts of completely tempered steel have to be rendered soft,
these parts are heated to a red heat and then cooled in soap suds.
This is done with the tangs of files, knives, swords, saws, etc.
Soluble organic substances retard the tempering process in proportion
to the quantity used, and thus lessen the effect of pure water. Such
substances (e. g., milk, sour beer, etc.) are employed only to a
limited extent.
«To Caseharden Locally.»—In casehardening certain articles it is
sometimes necessary, or desirable, to leave spots or sections in the
original soft uncarbonized condition while the remainder is carbonized
and hardened. This may be effected by first covering the parts to be
hardened with a protecting coat of japan, and allowing it to dry.
Then put the piece in an electroplating bath and deposit a heavy coat
of nickel over the parts not protected by the japan. The piece thus
prepared may be treated in the usual manner in casehardening. The coat
of nickel prevents the metal beneath being carbonized, so it does not
harden when dipped in the bath.
A plating of copper answers the same purpose as nickel and is often
used. A simpler plan, where the shape of the piece permits, is to
protect it from the action of the carbonizing material with an iron
pipe or plate closely fitted or luted with clay. Another scheme is to
machine the parts wanted soft after carbonizing but before hardening.
By this procedure the carbonized material is removed where the metal is
desired soft, and when heated and dipped these parts do not harden.
«To Harden a Hammer.»—To avoid the danger of “checking” a hammer at
the eye, heat the hammer to a good uniform hardening heat and then dip
the small end almost up to the eye and cool as quickly as possible by
moving about in the hardening bath; then dip the large end. To harden a
hammer successfully by this method one must work quickly and cool the
end dipped first enough to harden before the heat is lost on the other
end. Draw the temper from the heat left about the eye. The result is a
hammer hard only where it should be and free from “checks.”
«Hardening Steel Wire.»—Pass the steel wire through a lead bath heated
to a temperature of 1,200° to 1,500° F. after it has previously been
coated with a paste of chalk, so as to prevent the formation {685} of
oxides. The wire is thus heated in a uniform manner and, according to
whether it is desired hard or elastic, it is cooled in water or in oil.
«Hardening of Springs.»—A variety of steel must be chosen which is
suitable for the production of springs, a very tough quality with about
0.8 per cent of carbon being probably the best. Any steel works of
good reputation would no doubt recommend a certain kind of steel. In
shaping a spring, forging and hammering should be avoided if possible.
In forging, an uneven treatment can scarcely be avoided; one portion
is worked more than the other, causing tensions which, especially in
springs, must be guarded against. It is most advantageous if a material
of the thickness and shape of the spring can be obtained, which, by
bending and pressing through, is shaped into the desired spring. Since
this also entails slight tension, a careful annealing is advisable, so
as to prevent cracking or distorting in hardening. The annealing is
best conducted with exclusion of the air, by placing the springs in a
sheet-iron box provided with a cover, smearing all the joints well up
with loam. The heating may be done in a muffled furnace; the box, with
contents, is, not too slowly, heated to cherry red and then allowed
to cool gradually, together with the stove. The springs must only be
taken out when they have cooled off enough that they will give off no
hissing sound when touched by water. In order to uniformly heat the
springs for hardening, a muffle furnace is likewise employed, wherein
they are heated to cherry-red heat. For cooling liquid, a mixture of
oil, tallow, and petroleum is employed. A mass consisting of fish oil,
tallow, and wax also renders good service, but one should see to it
that there is a sufficient quantity of these cooling liquids, so that
the springs may be moved about, same as when cooled in water, without
causing an appreciable increase in the temperature of the liquid.
In most cases too small a quantity of the liquid is responsible for
the many failures in hardening. When the springs have cooled in the
hardening liquid, they are taken out, dried off superficially, and the
oil still adhering is burned off over a charcoal fire. This enables one
to moderate the temper according to the duration of the burning off
and to produce the desired elasticity. An even heating being of great
importance in hardening springs, the electric current has of late been
successfully employed for this purpose.
«To Temper a Tap.»—After the tap has been cut and finished heat it in
a pair of tongs to a blood-red heat over a charcoal fire or the blue
flame of a Bunsen burner or blow pipe, turning it around so that one
point does not get heated before another. Have ready a pail of clean,
cold water, into which a handful of common salt has been put. Stir the
water in the pail so that a whirlpool is set up. Then plunge the tap,
point first and vertically, into the vortex to cool. The turning of
the tap during heating, as well as the swirl of the quenching water,
prevents distortion. In tempering, the temper of the tap requires to
be drawn to a light straw color, and this may be done as follows: Get
a piece of cast-iron tube about 3 inches in diameter and heat it to a
dull-red heat for about 4 inches of its length. Then hold the tap, with
the tongs, up the center of the tube, meanwhile turning the tap around
until the straw color appears all over it. Then dip the tap in the
water, when it will be found perfectly hard. The depth of the color,
whether light or dark straw, must be determined by the nature of the
cast steel being used, which can be gained only from experience of the
steel.
«Scissors Hardening.»—The united legs of the scissors are uniformly
heated to a dark cherry red, extending from the point to the screw or
rivet hole. This may be done in the naked fire, a feeble current of
air being admitted until the steel commences to glow. Then the fire is
left to itself and the scissor parts are drawn to and fro in the fire,
until all the parts to be hardened show a uniform dark cherry red. The
two legs are hardened together in water and then tempered purple red to
violet.
The simultaneous heating, hardening, and tempering of the parts
belonging together is necessary, so that the degree of heat is the same
and the harder part does not cut the softer one.
In accordance with well-known rules, the immersion in the hardening
bath should be done with the point first, slowly and vertically up to
above the riveting hole.
«Hardening without Scaling.»—Articles made of tool steel and polished
may be hardened without raising a scale, thereby destroying the polish,
by the following method: Prepare equal parts in bulk of common salt
and (fine) corn meal, well mixed. Dip the article to be hardened first
into water, then into the mixture and place it carefully into the fire.
When hot enough to melt the mixture, take from {686} the fire and dip
or roll in the salt and meal, replace in the fire and bring to the
required heat for hardening. Watch the piece closely and if any part
of it shows signs of getting dry, sprinkle some of the mixture on it.
The mixture, when exposed to heat, forms a flux over the surface of the
steel which excludes the air and prevents oxidation, and when cooled in
water or oil comes off easily, leaving the surface as smooth as before
heating. Borax would possibly give the same result, but is sometimes
difficult to remove when cold.
«Hardening with Glycerine.»—I.—The glycerine employed must be of the
density of 1.08 to 1.26 taken at the temperature of 302° F. Its weight
must be equal to about 6 times the weight of the pieces to be tempered.
For hard temper add to the glycerine 1/4 to 4 per cent of sulphate
of potash or of manganese, and for soft temper 1 to 10 per cent of
chloride of manganese, or 1 to 4 per cent of chloride of potassium. The
temperature of the tempering bath is varied according to the results
desired.
II.—Glycerine, 8,000 parts, by weight; cooking salt, 500 parts, by
weight; sal ammoniac, 100 parts, by weight; concentrated hydrochloric
acid, 50 parts; and water, 10,000 parts, by weight. Into this liquid
the steel, heated, for example, to a cherry red, is dipped. A reheating
of the steel is not necessary.
«To Remove Burnt Oil from Hardened Steel.»—To remove excess oil
from parts that have been hardened in oil, place the articles in a
small tank of gasoline, which, when exposed to the air, will dry off
immediately, allowing the part to be polished and tempered without the
confusing and unsightly marks of burnt oil.
«VARIOUS RECIPES:»
«To Put an Edge on Steel Tools.»—Aluminum will put an edge on fine
cutting instruments such as surgical knives, razors, etc. It acts
exactly like a razor-hone of the finest quality. When steel is rubbed
on the aluminum, as, for instance, in honing a knife blade, the metal
disintegrates, forming an infinitely minute powder of a greasy unctuous
quality that clings to steel with great tenacity and thus assists in
cutting away the surface of the harder metal. So fine is the edge
produced that it can in no wise be made finer by the strop, which used
in the ordinary way merely tends to round the edge.
«To Restore Burnt Steel.»—To restore burnt cast steel heat the piece to
a red heat and sprinkle over it a mixture of 8 parts red chromate of
potassium; 4 parts saltpeter; 1/8 part aloes; 1/8 part gum arabic;
and 1/4 part rosin.
«To Remove Strains in Metal by Heating.»—In making springs of piano
wire, or, in fact, any wire, if the metal is heated to a moderate
degree the spring will be improved. Piano or any steel wire should be
heated to a blue, brass wire to a degree sufficient to cause tallow to
smoke. Heating makes the metal homogeneous; before heating, it is full
of strains.
If a piece of metal of any kind is straightened cold and then put
into a lathe and a chip turned off, it will be far from true. Before
turning, it was held true by the strain of the particles on the
outside, they having changed position, while the particles near the
axis are only sprung. The outside particles being removed by the lathe
tool, the sprung particles at the center return to their old positions.
If, after straightening, the metal is heated to a temperature of
400° F., the particles settle together and the strains are removed.
This is the case in the manufacture of saws. The saw is first hardened
and tempered and then straightened on an anvil by means of a hammer.
After it is hammered true, it is ground and polished a little, then
blued to stiffen it and then is subjected to the grinding process.
Before bluing, the metal is full of strains; these are entirely removed
by the heat required to produce the blue color. Often a piano-wire
spring will not stand long wear if used without heating, while if
heated it will last for years.
«To Render Fine Cracks in Tools Visible.»—It is often of importance to
recognize small cracks which appear in the metal of the tools. For
this purpose it is recommended to moisten the fissured surface with
petroleum; next rub and dry with a rag and rub again, but this time
with chalk. The petroleum which has entered the cracks soon comes out
again and the trace is plainly shown by the chalk.
«To Utilize Drill Chips.»—There is one modern machining process that
produces a shaving that has more value than that of mere scrap, and
that is drilling rifle barrels with the oil-tube drill. The cutting
edge of this drill is broken up into steps and the chips produced
are literally shavings, being long hair-like threads of steel. These
shavings are considerably used in woodworking factories for smoothing
purposes. {687}
«To Remove Fragments of Steel from Other Metals.»—The removal of broken
spiral drills and taps is an operation which even the most skillful
machinist has to perform at times. A practical process for removing
such broken steel pieces consists in preparing in a suitable kettle
(not iron) a solution of 1 part, by weight, of commercial alum in 4 to
5 parts, by weight, of water and boiling the object in this solution
until the piece which is stuck works itself out. Care must be taken to
place the piece in such a position that the evolving gas bubbles may
rise and not adhere to the steel to protect it from the action of the
alum solution.