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Carburizing By Gas
The process of carburizing by gas, briefly mentioned on page ...

Application To The Automotive Industry
The information given on the various parts of the Liberty eng...

Quenching The Work
In some operations case-hardened work is quenched from the bo...

Heat Treatment Of Punches And Dies Shears Taps Etc
HEATING.--The degree to which tools of the above classes shou...

Tempering Colors On Carbon Steels
Opinions differ as to the temperature which is indicated by t...

Tensile Properties
Strength of a metal is usually expressed in the number of pou...

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

The Theory Of Tempering
Steel that has been hardened is generally harder and more br...

Robert Mushet
Robert (Forester) Mushet (1811-1891), born in the Forest of D...

Lathe And Planer Tools
TO FORGE.--Gently warm the steel to remove any chill is parti...

Tempering Round Dies
A number of circular dies of carbon tool steel for use in too...

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

Using Illuminating Gas
The choice of a carburizing furnace depends greatly on the fa...

Hardening Carbon Steel For Tools
For years the toolmaker had full sway in regard to make of st...

The Packing Department
In Fig. 56 is shown the packing pots where the work is packe...

Detrimental Elements
Sulphur and phosphorus are two elements known to be detrimen...

Gas Consumption For Carburizing
Although the advantages offered by the gas-fired furnace for ...

William Kelly's Air-boiling Process
An account of Bessemer's address to the British Association w...

Annealing Alloy Steel
The term alloy steel, from the steel maker's point of view, r...

Heat Treatment Of Axles
Parts of this general type should be heat-treated to show the...

Complete Calibration Of Pyrometers


For the complete calibration
of a thermo-couple of unknown electromotive force, the new couple
may be checked against a standard instrument, placing the two bare
couples side by side in a suitable tube and taking frequent readings
over the range of temperatures desired.

If only one instrument, such as a millivoltmeter, is available,
and there is no standard couple at hand, the new couple may be
calibrated over a wide range of temperatures by the use of the following

Water, boiling point 212 deg.F.
Tin, under charcoal, freezing point 450 deg.F.
Lead, under charcoal, freezing point 621 deg.F.
Zinc, under charcoal, freezing point 786 deg.F.
Sulphur, boiling point 832 deg.F.
Aluminum, under charcoal, freezing point 1,216 deg.F.
Sodium chloride (salt), freezing point 1,474 deg.F.
Potassium sulphate, freezing point 1,958 deg.F.

A good practice is to make one pyrometer a standard; calibrate it
frequently by the melting-point-of-salt method, and each morning
check up every pyrometer in the works with the standard, making the
necessary corrections to be used for the day's work. By pursuing
this course systematically, the improved quality of the product
will much more than compensate for the extra work.

The purity of the substance affects its freezing or melting point.
The melting point of common salt is given in one widely used handbook
at 1,421 deg.F., although chemically pure sodium chloride melts at
1,474 deg.F. as shown above. A sufficient quantity for an extended
period should be secured. Test the melting point with a pyrometer
of known accuracy. Knowing this temperature it will be easy to
calibrate other pyrometers.

Next: Placing Of Pyrometers

Previous: Calibration Of Pyrometer With Common Salt

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