A two-foot bar of
steel will be 1/4 inch longer when red hot than when cold.
The temperatures of iron correspond to the following colors:
Dullest red seen in the dark... 878
Dullest red seen in daylight... 887
Dull red....................... 1100
Full red....................... 1370
Light red...................... 1550
Orange......................... 1650
Light orange................... 1725
Yellow......................... 1825
Light yellow................... 1950
_Bending Pipes and Tubes._--It is difficult to make bends or curves in
pipes and tubing without leaving a noticeable bulge at some point of the
work. Seamless steel tubing may be handled without very great danger of
this trouble if care is used, but iron pipe, having a seam running
lengthwise, must be given special attention to avoid opening the seam.
Bends may be made without kinking if the tube or pipe is brought to a full
red heat all the way around its circumference and at the place where the
bend is desired. Hold the cool portion solidly in a vise and, by taking
hold of the free end, bend very slowly and with a steady pull. The pipe
must be kept at full red heat with the flames from one or more torches and
must not be hammered to produce the bend. If a sufficient purchase cannot
be secured on the free end by the hand, insert a piece of rod or a smaller
pipe into the opening.
While making the bend, should small bulges appear, they may be hammered
back into shape before proceeding with the work.
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