Many articles that are made or formed into cups from thick metal may be so formed without the use of a pressure plate, whereas the pressure plate would be essentially necessary with the thinner metals. The separate pressure plate of a drawing press would generally be used in the process of making any article having a flanged top.

Fig. 149.

The three seta of combination cutting and cupping tools, figs. 150, 151, and 152, are in the position that they would have reached, after passing their blanks through the die. These and similar tools are worked in a double-action press, as they cut out and cup the blank at one stroke of the press. The sketches give a section through the tools, and they illustrate the construction of three different ways by means of which the punches are attached to their respective rams or slides. In tools of this kind it is essential that the two punches be made and fitted perfectly true and in alignment to each other to enable good work to result.

Fig. 150.

Referring to fig. 150, the cutting punch D P is screwed into the inner ram by means of a steel rod, known as a

"tommy lever,"being placed in the hole L for this purpose, having firmly secured D P to a. The outer or cutting punch C P is now passed over the drawing punch, and brought up to the bottom face of the outer slide 6. The fact of the drawing punch being inside the cutting punch makes the tools practically self-setting, as both punches when they come together, are in.perfect alignment. The punch C P is fixed firmly against the face H of the outer slide b by the hook-headed bolts d, the shank of the bolts passing through the hole 0. The face e of the punch C P cuts out the blank and pushes the blank into hole e1 of the die D1. And since the ram a is a sliding fit in slide b, when this slide b comes to rest, the face e of punch C P holds the blank in position, whilst punch D P forces the blank through the die to form the cup, during which process the blank is drawn or dragged from the face c by the down stroke of the drawing punch D P.

Fig. 151.

Fig. 152.

At the bottom of the cupping die a small bevel is seen at K, this to some extent prevents the chipping that frequently takes place at the bottom edge of the die, and which is the result of the excessive friction due to the action of drawing. This chipping action or breaking away at the bottom edge of the die during the process of heavy drawing due to the excessive pressure often results in the bursting of the die.

Immediately below fig. 150 will be seen an inverted plan of the two punches, H being the face on to which the hook-headed bolts come, e the face of the cutting punch, and D P the end of the cupping punch.

Figs. 151 and 152 do not need full explanation, as the same lettering is used as in the case of fig. 150. In fig. 151 the bolts are dispensed with, as the cutting punch is screwed into the outer slide, and in fig. 152 the cutting punch C P, being turned to just enter the hole in the outer slide, set pins are passed down through the flange of the outer slide, and screwed into collar H of the punch. In this case the cupping punch is pushed up from the bottom of the hole in punch C P. Bring the cupping punch into perfect alignment, ready to be fixed by some form of gartering at I. To prevent the punch D P dropping down, the garter key may be fixed in the ram at W, whilst the slot N allows the gartering to be done without removing the inner ram.

Referring again to the breaking away at the bottom edge of a drawing die, this edge must be a sharp corner, since this corner is practically all that is to prevent the cup from re-entering the die upon the return stroke of the drawing punch. This edge has also to act as an extractor or stripper, to remove the cup from the drawing punch. When drawing cup-shaped articles or re-drawing shells and similar work, llwp after the cup or shell has passed through the die, a slight expansion of the metal article takes place at the top edge; this expansion or springing is the result of the elasticity of the metal, and, as a rule, expands the top of an article sufficient to prevent it being drawn up again through the drawing die upon the return stroke of the punch.

Fig 153.

Fig. 153 gives three different styles of finishing the corner or bottom edge of the die: A is made perfectly square or a right angle; B has been finished by a round-nosed turning tool being brought up against the edge; and C is finished at an angle of 45 degs. with the bottom of the die. This finish C is by far the strongest, and gives better all-round results in working.

Fig. 154 shows the difference between an ordinary cupping die and a re-drawing die. The cupping die is bored or recessed at the top to a depth equal to the thickness of the blank. The blank is dropped into this recess, and held central whilst the cupping punch moves down to its work; or, instead of recessing the cupping die, there may be a guide plate fastened to the top of the bolster. In the case of the re-drawing die, fig. 154, this die is bored out to receive the shell, and is usually recessed to a sufficient depth to hold the shell upright and steady whilst the re-drawing punch enters the shell to begin the work of re-drawing.

When re-drawing or extending long shells of small diameter, it is frequently very difficult to remove the shell from the drawing punch. This is particularly so when the metal is very thin, there being no strength at the top edge of the shell to engage the sharp edge of the die bottom. A good method to overcome this difficulty is seen at fig. 155, where it will be noticed that special slides are fitted to the bottom of the die bolster B, and held in position by a plate, these slides being drawn up to the punch by means of small springs. Beginning at the left-hand side of the sketch. In the first process a punch P is about to begin re-drawing the metal shell S, and pass it through the die D. The second figure gives the position of the tools after the re-drawing has commenced, and the shell has forced the small slides X X out of the way. In the third figure the re-drawing process has been completed, when the small slides X X have been drawn up to the punch under the action of the springs, andi the slides X X have, as it were, clipped over the top of the long shell. The fourth figure shows that the drawing punch has been withdrawn from the die upon the return stroke of the press, and the sharp edges of the little slides X X have clipped over the shell and up to the punch, and prevented the metal shell S from following the punch.

Fig. 155.