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Hardening
The forgings can be hardened by cooling in still air or quen...

The Leeds And Northrup Potentiometer System
The potentiometer pyrometer system is both flexible and subst...

Typical Oil-fired Furnaces
Several types of standard oil-fired furnaces are shown herew...

Short Method Of Treatment
In the new method, the packed pots are run into the case-har...

Placing The Thermo-couples
The following illustrations from the Taylor Instrument Compan...

Instructions For Working High-speed Steel
Owing to the wide variations in the composition of high-speed...

Critical Points
One of the most important means of investigating the properti...

Effect Of Different Carburizing Material
[Illustrations: FIGS. 33 to 37.] Each of these different p...

Furnace Data
In order to give definite information concerning furnaces, fu...

Crucible Steel
Crucible steel is still made by melting material in a clay or...

Annealing Of Rifle Components At Springfield Armory
In general, all forgings of the components of the arms manufa...

Alloying Elements
Commercial steels of even the simplest types are therefore p...

Tungsten
Tungsten, as an alloy in steel, has been known and used for a...

Silicon
SILICON is a very widespread element (symbol Si), being an es...

Cyanide Bath For Tool Steels
All high-carbon tool steels are heated in a cyanide bath. Wi...

Steel Before The 1850's
In spite of a rapid increase in the use of machines and the ...

The Effect Of Tempering On Water-quenched Gages
The following information has been supplied by Automatic and ...

Leeds And Northrup Optical Pyrometer
The principles of this very popular method of measuring tempe...

The Care Of Carburizing Compounds
Of all the opportunities for practicing economy in the heat-t...

S A E Heat Treatments
The Society of Automotive Engineers have adopted certain heat...



The Modern Hardening Room






Category: HARDENING CARBON STEEL FOR TOOLS

A hardening room of today means a very
different place from the dirty, dark smithshop in the corner with
the open coal forge. There, when we wanted to be somewhat particular,
we sometimes shoveled the coal cinders to one side and piled a great
pile of charcoal on the forge. We now have a complete equipment;
a gas- or oil-heating furnace, good running water, several sizes
of lead pots, and an oil tank large enough to hold a barrel of
oil. By running water, we mean a large tank with overflow pipes
giving a constant supply. The ordinary hardening room equipment
should consist of:

Gas or oil muffle furnace for hardening.
Gas or oil forge furnace.
A good size gas or oil furnace for annealing and case-hardening.
A gas or oil furnace to hold lead pots.
Oil tempering tank, gas- or oil-heated.
Pressure blower.
Large oil tank to hold at least a barrel of oil.
Big water tank with screen trays connected with large pipe from bottom
with overflow.
Straightening press.
The furnace should be connected with pyrometers and tempering tank with
a thermometer.

Beside all this you need a good man. It does not make much difference
how completely the hardening department is fitted up, if you expect
good work, a small percentage of loss and to be able to tackle anything
that comes along, you must have a good man, one who understands
the difference between low- and high-carbon steel, who knows when
particular care must be exercised on particular work. In other
words, a man who knows how his work should be done, and has the
intelligence to follow directions on treatments of steel on which
he has had no experience.

Jewelers' tools, especially for silversmith's work, probably have
to stand the greatest punishment of any all-steel tools and to
make a spoon die so hard that it will not sink under a blow from
an 1,800-lb. hammer with a 4-ft. drop, and still not crack, demands
careful treatment.

To harden such dies, first cover the impression on the die with
paste made from bone dust or lampblack and oil. Place face down
in an iron box partly filled with crushed charcoal, leaving back
of die uncovered so that the heat can be seen at all times. Heat
slowly in furnace to a good cherry red. The heat depends on the
quality and the analysis of steel and the recommended actions of
the steel maker should be carefully followed. When withdrawn from
the fire the die should be quenched as shown in Fig. 80 with the
face of die down and the back a short distance out of the water.
When the back is black, immerse all over.



If such a tank is not at hand, it would pay to rig one up at once,
although a barrel of brine may be used, or the back of the die
may be first immersed to a depth of about 1/2 in. When the piece
is immersed, hold die on an angle as in Fig. 81.



This is for the purpose of expelling all steam bubbles as they
form in contact with hot steel. We are aware of the fact that a
great many toolmakers in jewelry shops still cling to the overhead
bath, as in Fig. 82, but more broken pieces and more dies with
soft spots are due to this method than to all the others combined,
as the water strikes one spot in force, contracting the surface
so much faster than the rest of the die that the results are the
same as if an uneven heating had been given the steel.





Next: Take Time For Hardening

Previous: Hardening Carbon Steel For Tools



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