Triple Action.— Triple-action dies are in tended to punch, draw and stamp the work at the same stroke of the press. The con struction is the same as the double-action, ex cept that the die block is cut away to allow the stamping die to be set in place, and the shell is carved down to the stamping die and °struck up)) between that and the matrix formed on the end of the drawing punch; as the punch rises, the work is stripped from the punch by the °pull off,* and is removed from the dies by the use of an inclined press, or by a swinging arm attached to, and operated by the press, that catches the work as it falls from the punch.
This style of die is largely used on black ing-box covers, lard-pail lids, or other work where a stamped or embossed cover is wanted. A die of this class should always be used in an arched press, as the strain of the stamping process is very severe on the aopen back') style press, and is apt to crack the body of the press. In making a drawing die, use a steel that is high in carbon, and if it shrinks a little in hardening so much the better. There is on the market at least one grade of steel which will stand three success ive hardenings, and will shrink each time so that the die as it wears out can be °shrunk up° and then ground out to sift again.
Various modifications of a drawing die are necessary in order to successfully draw up the different metals. Zinc works better when the soap suds, or whatever lubricant may be employed, is used hot as possible, as that metal works much better at a heat of 125 degrees.
After a cup, basin, etc., has been drawn, to reduce its diameter still more and make it deeper, redrawing dies are used.
Thick In drawing very thick work the drawing die can be made bell-mouthed, as the thickness of the metal will reduce the tendency to crimp or pucker. The same method of making the die is followed when it is desired to draw a shell that is very short in proportion to its diamater.
The possibilities of what can be done by this method of forming up sheet metal are almost unlimited; trunks, wheelbarrows, sinks, and the copper boiler for hot-water service are every day productions at the present time.
The great secret of drawing up work is to have good metal, and to properly adjust the blank-holder, so as to hold the metal just hard enough to prevent it from puckering. In drawing up metal It should be borne in mind that it will flow where it can go the easiest.