Tempering Round Dies

: The Working Of Steel

A number of circular dies of carbon tool steel for use in tool

holders of turret lathes were required. No proper tempering oven

was available, so the following method was adopted and proved quite


After the dies had been hardened dead hard in water, they were

cleaned up bright. A pair of ordinary smiths' tongs was made with

jaws of heavy material and to fit nicely all around the outside of

the die, leaving a 3/32-in. space when the jaws were closed around

the die. The dies being all ready, the tongs were heated red hot, and

the dies were picked up and held by the tongs. This tempered them

from the outside in, left the teeth the temper required and the

outside slightly softer. The dies held up the work successfully

and were better than when tempered in the same bath.