BLANKING DIES.
These are made for cutting out flat blanks from steel, iron, paper, etc. Usually both punch and die are hardened and tempered; sometimes the punch is left soft, and as it gets worn is set out and refitted by being forced or shoved into the die; sometimes it is best to reverse this operation, as in punching paper, playing cards, etc., and harden the punch and leave the die soft.
shear or slightly beveled edge is usually given to the punch or die, determined by the work it has to do; when it is intended to use the blanks, or pieces punched out, the shear should be given to the die, as less distortion is given to the metal by this method, but where the hole is the object sought, as in rivet holes in boiler plates, etc., the shear should be given to the punch.
Cutting or blanking dies are usually held in a shoe or die-holder, or if a large die, it is fastened to the bed of the press direct, but as a rule the fewer pieces interven ing between the press and the die the better re sults will be obtained. Very large blanking dies are usually made in one of two ways: either as rings set in a cast-iron holder, or by welding the rings directly on to a wrought-iron holder or die-plate; the latter method is the best in making plain dies, but cannot be used in com pound dies. The welding of the steel rings to
gether, and then on to the wrought-iron plate, calls for good work on the part of the smith. In the former method the rings are first welded and then turned, hardened and ground true in the universal grinder, then set in a groove turned in the holder and held there by being bolted from the back of the holder.
Hot In making dies for hot work (as the blanking out of nuts and other thick work from red-hot metal) a die made of chilled cast-iron with a good clearance will give good results, as the temper is not affected by the heat of the stock punched, the punch being made of steel and fitting the die loosely (in very thick stock a difference of life" or more in the diameter of the punch and die is not too much), and if a nice job is wanted, the work can be shaved, or repunched, as it is called, by forcing it through a second die that is a trifle smaller than the first, leaving a true and smooth surface.
In the repunching of brass and copper, the use of buttermilk as a lubricant gives a better result than any oil or soap water.