Forging: Manual of Practical Instruction in Hand Forging of Wrought Iron ... by John Jernberg

Author:John Jernberg
Language: eng
Format: epub
Publisher: American Technical society
Published: 1919-03-25T05:00:00+00:00

Fig. 123. Typical Views of Cold Chisel

an end of this sort that may be broken off after the tempering is done. When hardening, a chisel should be heated red hot about as far back from the cutting edge as the point A, Fig. 124. Care must be taken to heat slowly enough to keep the part being heated at a

uniform temperature throughout. If the point becomes /^ overheated, it should not be dipped in water to cool

off, but should be allowed to cool in the air to below the hardening heat and then reheated more carefully. When properly heated, the end should be hardened by dipping in cold water to the point B. As soon as the end is cold, the chisel should be withdrawn from the water and the end polished bright by rubbing with a piece of emery paper. The part of the chisel from "A A to B will still be red hot arid the heat from this / H part will gradually reheat the hardened point. As

j J__« thk c °ld P ar t ls reheated, the polished surface will

change color showing at first yellow, then brown, and at last purple. As soon as the purple (almost a blue color) reaches the nick at the end, the chisel should be completely cooled. The waste end may now be snapped He^fi'ng 2 and °^ an ^ *ke 8 ra * n examined. If the grain is too coarse, H ArIas ng the tool should be rehardened at a lower temperature, while if the metal is too soft, and the end bends without breaking, it should be rehardened at a higher temperature. Cape Chisel. This is a chisel used for cutting grooves, key-seats, etc. The end A x Fig. 125* should be wider than the rest of the

FORGING

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blade back to B. The chisel is started by thinning down B with two fullers, or over the horn of the anvil as shown at A, Fig. 126. The

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