Table V.-Example In Drawing Metal Cartridge Shell„

importance to be remembered is that, even when a comparatively sharp corner is required on the work, it is not advisable to make the drawing corner of a punch too sharp, or it will tend to cut and tear the metal.

Fig. 143.

A set of successive piercing and blank cutting tools are shown at fig. 143. The wrought-iron holder B is bored out at H to receive the piercing punch P, and the cutting-out punch P1. The distance between these two punches centre to centre, is equal to the diameter of the washer blank plus the amount of scrap or waste metal necessary between each pair of blanks. The metal M is passed along to cover the die, when punch P1 cuts out the small blank P B, this makes the hole in the washer and may therefore be called the piercing bit P B of the washer.

Fig. 144.

The motion of the press next moves the slide carrying the punches up to the top of the stroke, whilst the operator or feed rolls, as the case may be, move the metal M forward. On the next down stroke, the guide peg G finds the hole in the centre of the washer which has been pierced on the preceding down stroke, and the punch P cuts out the actual washer blank W, at the same time the smaller punch P1 makes a hole in the part of the metal from which the next washer blank will be cut. At fig. 144, M, the scrap metal is seen as it would appear after the press has made two down strokes. A

Fig. 145.

Fig 146.

Complete washer ready holed has been cut from W and the piercing bit of another washer has been cut from P1 B1 in the metal scrap. The washer W is seen in plan at tig. 145. The stamp die, fig. 146, seen in part section S D, is used for stamping the bevel upon the outer edge of the washer and rounding the edge of the hole in the washer. This is a point of importance as it ensures the washer bedding up well under the head of any bolt upon which it may be used, thereby preventing the trouble which might be caused if a sharp edge was left on the hole of a washer; for should a bolt happen to be a tight fit, it might be necessary to ease the hole by filing. This may seem to some mechanics a small point, but it is of importance to remove the frase from the hole in the same stamp die that does the beveling on account of the cheapness of the method as compared to filing the frase from each washer separately.

Fig. 147.

The set of tools fig. 147 would be used to produce a similar washer; but these tools would cut and hole the washer at one blow. P is the punch, having a shank A to fit the hole in the slide. The punch P works over the die D and forms cutting edges both inside and outside the die,

Fig. 148.

E1 and E2 being the cutting edge for the outside diameter of the washer blank, the hole being pierced by the cutting edges E3and E4 At the centre part of the punch a ring R, R', shown in section, is provided with a spring, acting behind it. This is to force the washer out from the punch. Another ring, R1, R1, shown upon the die, is backed up by another spring, so as to raise the scrap metal from the die. These extractor rings are sometimes backed up by means of an indiarubber ring or washer, which acts as the backing-up spring. One form of combination tools is seen at fig. 148. These tools are used for cutting out a blank and raising it into a thin metal cap E. The edges E1 and E2 on the punch P cuts out the blank. The punch, in its travel on the down stroke, forces the blank down between the walls E3 and E4 of the die D. Inside the die is an anvil or raising peg A, and the tools are set in such a position that when the punch reaches the bottom of its stroke the face F of the punch just brings sufficient pressure upon the top of the anvil, or forming peg, to form the metal cap E. During the operation the punch and blank, in the down stroke, will have forced down the ring R, R, thereby causing the rubber backing-up ring to be compressed. Upon the return stroke of the punch this extractor ring R, R will again return to the position shown in fig. 148, enabling the cap E to be lifted out of the die. The same cap E may be made in a different set of tools, fig. 149. In this case the tools are made for a double-action press. The lower die D is fastened to the bed of a power press, and the combined cutting or blanking punch, and blank holder B P, is worked by the outer slide, and moves slightly in advance of the drawing punch D P, which is actuated by the inner slide. The outer slide of the double-action press is so arranged that, after making its stroke to cut out the blank, it stops during about one quarter of the revolution of the crank-shaft. The blank having been cut from the sheet metal by the cutting edges C, C1, it is now passed down and held between the face a, a1 of the punch and the face e, e of the inside of the die, during the down dwell of the outer slide, whilst the blank is held here by a pressure which can be regulated according to the requirements of each particular case. The drawing punch D P, which is connected to a second or inner slide, continues its downward movement, thereby drawing the metal from between the pressing surfaces a, a1 and e, e into the required shape. It will be readily understood that in this manner the metal is prevented from wrinkling or puckering during the drawing or raising process. In this set of tools, fig. 149, the face a, a1 of the blanking punch acts as the pressure plate-instead of using a special pressure plate-to prevent the wrinkling or puckering of the metal, besides doing the cutting out. The puckering of the metal is more likely to occur when drawing thin blanks than with thick ones.