DIES AND DIE MAKING. In the manu facture of machinery by the modern duplicate system, in which every individual part is so nearly alike that it may be replaced for any other broken or worn part, the art of the die maker has become of great importance. The majority of working parts of machines— prac tically all but the heavy castings — are now made by machine forging, the rough metal stock being fed into presses, and cut and stamped into desired shapes. See MACHINE FORGING.
In order that the forging machine or press may do its work, it must be provided with dies for shaping the stock that is pressed or squeezed between them. Dies are commonly made in pairs, as shown in Fig. 1, the halves being termed male and female. They have to be formed with great accuracy, and require square, sharp, strong cutting or forming edges, and must be tempered as hard as is consistent with toughness. They may be designed in many ways. If it is desired to stamp washers out of thin metal, with a central hole of half inch diameter and one and a half inches over all, one pair of dies could be made to punch out the hole, wasting the half-inch center of metal, and another pair of dies to punch out the washer itself, wasting the spaces between the inch and a half circles. Or gang dies could be made, to punch out say 10 holes at a time, while another pair of gang dies at a following opera tion punched out the 10 washers complete. Or, better still, a progressive gang die could be made that would comprise both rows of half-inch punches and rows of inch and a half punches. This being placed in the press, and a long strip of metal fed in, and advanced at every stroke, so that the row of half-inch holes would be followed on the next stroke with the inch and a half gang, it is apparent that the press would turn out a series of complete washers at every stroke after the first. This outline will
enable the reader to recognize that in die mak ing the designer has to consider how many parts are likely to be made from the dies, and the greater the number the more labor and expense he is justified in putting in on the pair of dies to secure the largest output from the forging or stamping machine.
The first thing to be considered to determine whether a punch and die should be used to pro duce work is the number of pieces wanted. If it is standard work, and the demand is 100 or more per week, it is both desirable and economi cal to have a die for after the die is once made the work can be produced at a very low cost. Oftentimes when a large number of pieces are wanted, and a power feed is used, the cost will not exceed two cents per LOCO blanks.
The power required to blank out a piece of metal depends largely on the shape of the blank and the number of cutting inches in the die, a long narrow blank requiring more power than a round blank of the same area, the shear of the dies being equal. If the work will admit of the face of the punch being slightly round ing, less pressure will be required than with a flat-ended punch.
The making of dies calls for very expert workmanship both in design and execution, and the tempering requires an intimate knowledge of conditions and the consideration of the form and character of the die. A whole series of die shaping, milling and filing machines have been developed for the special use of the die maker.
Following are the more common types of dies used: