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Correction For Cold-junction Errors
The voltage generated by a thermo-couple of an electric pyrom...

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

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

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

Rate Of Absorption
According to Guillet, the absorption of carbon is favored by ...

Application Of Liberty Engine Materials To The Automotive Industry
The success of the Liberty engine program was an engineer...

Hardening Operation
Hardening a gear is accomplished as follows: The gear is tak...

Suggestions For Handling High-speed Steels
The following suggestions for handling high-speed steels are ...

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

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

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

It is considered good practice to quench alloy steels from th...

Heat-treating Equipment And Methods For Mass Production
The heat-treating department of the Brown-Lipe-Chapin Company...

Chrome-nickel Steel
Forging heat of chrome-nickel steel depends very largely on ...

Hardness Testing
The word hardness is used to express various properties of me...

Protectors For Thermo-couples
Thermo-couples must be protected from the danger of mechanica...

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

Standard Analysis
The selection of a standard analysis by the manufacturer is t...

Heating Of Manganese Steel
Another form of heat-treating furnace is that which is used ...

Pyrometry And Pyrometers
A knowledge of the fundamental principles of pyrometry, or th...

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.

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