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

The Thermo-couple
With the application of the thermo-couple, the measurement of...

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

Piston Pin
The piston pin on an aviation engine must possess maximum res...

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

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

Highly Stressed Parts
The highly stressed parts on the Liberty engine consisted of ...

Hardening High-speed Steels
We will now take up the matter of hardening high-speed steels...

Temperatures To Use
As soon as the temperature of the steel reaches 100 deg.C. (...

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

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

Heat-treating Department
The heat-treating department occupies an L-shaped building. ...

Refining The Grain
This is remedied by reheating the piece to a temperature slig...

A combination of the characteristics of nickel and the charac...

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

The Pyrometer And Its Use
In the heat treatment of steel, it has become absolutely nece...

Pickling The Forgings
The forgings were then pickled in a hot solution of either ni...

Steel Worked In Austenitic State
As a general rule steel should be worked when it is in the a...

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

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

Leeds And Northrup Optical Pyrometer


The principles of this very popular method of measuring temperature
are sketched in Fig. 123.

The instrument is light and portable, and can be sighted as easily
as an opera glass. The telescope, which is held in the hand, weighs
only 25 oz.; and the case containing the battery, rheostat and
milliammeter, which is slung from the shoulder, only 10 lb.

A large surface to sight at is not required. So long as the image
formed by the objective is broader than the lamp filament, the
temperature can be measured accurately.


Distance does not matter, as the brightness of the image formed
by the lens is practically constant, regardless of the distance
of the instrument from the hot object.

The manipulation is simple and rapid, consisting merely in the turning
of a knurled knob. The setting is made with great precision, due to
the rapid change in light intensity with change in temperature and
to the sensitiveness of the eye to differences of light intensity.
In the region of temperatures used for hardening steel, for example,
different observers using the instrument will agree within 3 deg.C.

Only brightness, not color, of light is matched, as light of only
one color reaches the eye. Color blindness, therefore, is no hindrance
to the use of this method. The use of the instrument is shown in
Fig. 127.

Next: Optical System And Electrical Circuit Of The Leeds & Northrup Optical Pyrometer

Previous: Placing The Thermo-couples

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