The advisability of using high-speed steel for punch-press blanking, bending, forming, and other dies, depends in a large measure on the facilities in the individual shop, for hardening tools made from this steel. If conditions are favorable, there is no doubt that many dies made from highspeed steel will produce several times the amount of work which the same die made from carbon steel will produce. This is especially true of forming, bending, and drawing dies, where there is crushing strain and a tendency to wear from abrasion.
Fig. 381. View of Dies of Sub-Press.
In making a die, as in making many other forms of tools, the principal item of expense is the labor; the difference in the cost of steel is insignificant when the life of the tool and the increased amount of work it will turn out are considered.
Dies made from high-speed steel should be pre-heated to a low red in some form of pre-heating furnace; then placed in a high-speed furnace and raised to a uniform temperature of from 1750° F. to 2100° F., after which they should be removed and immediately plunged into a bath of oil. Dies that are not to be subjected to great strain or extreme shock may be heated to the higher temperature mentioned, while those that are to be subjected to strains should receive lower heats. Different makes of steel require different temperatures on account of the varying percentages of alloys. As a result, exact temperatures cannot be definitely stated.
Fig. 382. A Pattern of Sub-Press.
After hardening, the temper should be drawn from 460° F. to 530° F., depending on the strain the tool is to receive. If the strains are excessive, the higher temperature must be given.