454 



Popular Science Monthly 



^ DRILL- 

 \ 



[HB E 



The die face, in this particular case, is 

 treated differently, as it is considerably 

 higher near the center than at the outside. 

 This gives a shearing cut on the stock, 

 doing the work with far 

 less power than if the die 

 face were perfectly flat. 

 The die must also have 

 clearance as shown by the 

 dotted lines. The hole is 

 straight for a short distance 

 ■ — about 1/32 in. — then it 

 becomes larger on a con- 

 stant taper, the amount 

 of taper being the same as 

 for the punch. This pro- 

 vides a clearance for the 

 punchings and permits 

 them to fall through easily. 

 The shallow hole in the 

 side of the die is for the re- 

 taining set screw shown 

 more clearly in Fig. 1, 



The die and punch 

 shown in Fig. 9 is for 

 making a five pointed star 

 in saucer shape. As this 

 product is in the punching 

 it must be formed in one operation. To 

 do this the die face is made flat an^ the 

 punch to shear, as shown. The amount of 



n 



3, 



I REO. 

 _^'ll\'i.\.QNt.R 



STRIPPER BASE -MACM.ST. 



STRIPPER plate: - MACH ST 



FIG. 6. 



16-T 



2REQ-7ALLCVER' 



SUPPORT CLIP ' MACH. ST. 



FIG. 7 



Details of the stripper 

 base and plate; also jaw 

 clips to hold the parts 



BLAIJKINC PUNCH 



FIG.6. 



rORMINC PUNCH 

 &Dlt 



FIC.9. 



CURLING PUNCH 

 ft DIE. 

 FIG. 10. 



Three kinds of dies and punches showing 

 their construction; also sample of work 



shear given to the punch face governs the 

 amount of bend in the i)ro(luf'1, and, in 

 special cases, it must be found by trial. 

 With this punch it will be seen that the 



points of the star are pierced first and are 

 forced through as the punch enters the 

 die, the punch continuing to shear the 

 stock and to bend it into the desired 

 shape. 



The concave to the 

 punch face is produced by 

 grinding. In the case of 

 very small punches, the 

 concave may be given by 

 drilling before the punch is 

 hardened, then, after the 

 hardening, lapped with a 

 piece of wood, oil an.d 

 emery. The flutes may 

 be chipped and filed, if 

 there is no means of mill- 

 ing them with a formed 

 cutter. 



The die is marked out 

 and drilled with a small 

 drill so that it does not 

 quite touch the outline or 

 cut into the next drilled 

 hole. To prevent the holes 

 breaking into one another, 

 fill the last drilled hole 

 with a metal plug. 

 Another metal part in which the punch- 

 ing is the product is shown in Fig. 10. 

 It is a complete ring. As in the other case, 

 the die face is left flat and the shear to the 

 punch face is all to one side as shown. The 

 angle of shear determines the diameter of 

 the finished ring. This also must be de- 

 termined by trial. 



If the face of the punch is made straight 

 on an angle it will require considerable 

 grinding throughout the cutting and 

 will have a very short life. To obviate 

 this wear, a short portion at the heel 

 should be made equal to about one-half 

 the thickness of the stock to be punched. 

 At the terminal of the ring there will ap- 

 pear a straight, flat part, equal to the 

 amount of the flat part on the punch. 

 This can be finished by grinding or ham- 

 mering. 



These holding devices are not expensive 

 to make, and" where there is a good-sized 

 vise at hand, small, round and square 

 punches and dies may be used to advan- 

 tage in punching holes in sheet metal for 

 ordinary riveting or for tapped holes in 

 fastening parts together with machine 

 screws. The punches and dies for these 

 operations are easily made. — J. B. Murphy. 



