Fig. 124.

These centre holes will afterwards serve to guide the drill for drilling the first sized hole in the bosses previous to their being finally corrected by a second drilling in a suitable jig. Upon the up stroke of the press the rods R, R, which are connected to the slide, would lift H, E, E, and thereby extract the article B from the die; B will now fall from the tools.

A

B

C

Fig. 185.

It will be noticed that the slide is shown in fig. 124 upon the top stroke, and the question may be asked, how can the next blank and pair of small bushes be placed into the die when the pegs E, E project above the top of the die ? The answer to this question will explain the value of the arrangement. As a matter of fact, the rods R, R are shown set in the wrong position, and to set the rods properly for the work now being performed in the press the nuts N, N must be unlocked, and rods R, R unscrewed sufficient to allow H and pegs E, E to fall down into such a position as to bring the tops of pegs E, E a distance below top of die, equal to about one-sixth the length of the bosses on the blank. This will allow the small bosses to be placed in the die, then when the punches come down in their travel they will force the bosses into the die until neither bosses, pegs, or H can be driven further. The punches will then complete their work. From this it will be seen that by lengthening or shortening rods R, R the bar H can be placed in any relative position when the slide is on the top of the stroke, these relative positions being obtained by giving more or less lost motion at the heads T, T of rods R, R during the up stroke. When H falls upon the bottom of slot in K-if the press slide has not completed its down stroke-the heads T, T will leave the steel anvil H. Therefore, whatever distance there is between bottom face of anvil H and the inside shoulders of heads T, T will be lost motion to anvil H upon the return stroke, because heads T, T must necessarily travel some distance before commencing to lift the anvil H. Fig. 126 is a plan and fig. 127 an end elevation of the die and bolster, fig. 128 being an inverted plan of the chuck for holding the punches. This principle of extractor can be greatly modified to accommodate the various requirements in either hand or power presses to suit different classes of work.

Fig. 126.

Fig. 127.

Fig. 128.

The bending of wire and metal strips usually refers to articles which have their surfaces moved into some new and permanent shape without their thickness being materially altered. They may, however, sometimes be slightly thinned at certain points, where the action of the bending tools have stretched them in bending a corner to some sharp curve or angle. When bending wire or strip metals it is sometimes difficult to decide upon the correct shape of tools to give the desired effect, since the metal will frequently spring back from the shape to which the tools have bent it part of the way towards its original shape. This is due to the elasticity of the metal, and varies according to its nature and temper. Lead and copper will give very little trouble in this way, but brass, iron, and steel are not so easy to manage. Fig. 129 represents a pair of tools for bending the steel wire D, D. The punch P, and the die D, would be made to press the wire into the form seen at N1, N1, but the wire, after being removed from the bending tools, would spring at the corner C into the position D, D. From this it will be readily understood that the bending tools must necessarily be made to bend the wire a sufficient distance to allow for its springing back. This frequently necessitates the altering of the curves on the bending tools after they have been tried. In the case of fig. 130 the springing action referred to would take place at both corners, C, C, the tools having been designed to carry the wire down to the shape shown at dotted lines N1, N1. The final outline of the article after the springing has occurred is indicated by D1, D1.

Fig. 131 illustrates the bending of a flat steel spring, S S. When bending curves and angles, similar to those contained in this kind of work, the springing back difficulty must necessarily be overcome by careful experiment. In addition to this, it is often advisable to ease away the tools at certain points. It would appear to a new beginner that the proper way to construct such tools would be to make the face of the bending punch P, and the face of die D, to fit the top and bottom sides of the spring respectively, so that when the bending tools are well up to their work the metal of the steel spring exactly fills the space between the faces of the punch and die. It is, however, found in practice to be much better for the working of the tools if they are eased off at certain points where the action of bending does not actually occur. There are several reasons for this. A little dirt may accumulate in the tools, the metal may not always be of an exact uniform thickness for its whole area, or the peculiar shape of the curves upon the tools may be such as to make it difficult for the toolmaker to ensure the tools fitting accurately the curves on either side of the metal spring, thereby leaving the exact same space between the tools for the whole length of their curves. This is a difficulty that could be overcome by careful toolmaking, but the rough nature of the work will scarcely warrant the expense of such care as would be required to carry this into effect. Particularly is this so by reason of the fact that by easing away the tools as before mentioned enables the bending to be done with very much less power required for the operation. Taking the case of the spring S, S, the punch would need to press hard at A, A, also at the bottom B, but it would be advisable to ease the punch away well at E, E, and it will further be noticed that the die has been eased away at two points a little below E, E, where a clear space is shown between the bottom of the spring and the die.

Fig. 130.

Fig. 131.

It frequently happens that large quantities of short lengths are required to be cut from long wire rods. An instance of this kind would occur in a hinge factory, where joint-wire rods would be required for connecting the two sections of the hinge together. There are also instances when wire rivets and similar wire lengths are required to be absolutely square at their ends when cut, and to be of standard length. Figs. 132 and 133 represent suitable tools for cutting wires of this kind. The casting C forms the bolster, and it is bored to receive the die D. This die is drilled straight through, parallel, to receive the wire W an easy fit. The die D is held firmly in position by set pins, which are screwed into the lugs L, L. The set pins are not shown in the sketch. Another part A, of the bolster C, is drilled and tapped central, and in perfect alignment with the hole in the die D, to receive the set pin S, which is locked in position by lock nut L N. This set pin may be adjusted to form any given distance between the end of set pin and face of die. If cutting rivets 3/4 in. long the distance between end of set pin and face of die will be set at 3/4 in., so that set pin S acts as a stop gauge, to which the wire is pushed by the hands of the operator

Fig. 132.

The punch P, fig. 133, works up and down close against the face of the die, and is slotted for a distance up to pass freely over the wire. The top of this slot is made the form of the wire to be cut so that the action of the punch whilst chopping or shearing, shall not damage the wire The die is made double ended (see fig. 132) so that both ends may be ground and used in their turn; and the fact of the die being a comparatively good length holds the wire sufficiently steady and square, although the wire may be an easy fit. Another example of chopping or shearing a rod is seen at fig. 134. R is a bright drawn steel rod, and would probably usually be supplied from the wire drawn in 12 ft. lengths. These rods, which are fig. 8 in section, will be finally sawn up into short pieces by means of slitting saws operated in a milling machine, but the 12 ft. lengths would be awkward to handle in the machine. They are, therefore, usually chopped or sheared up into, say, 4 ft. lengths, to enable the milling machine operator to handle them easily. The bottom shear blade B, would be about § in thick, and bolted on to a special bolster by bolts passing through holes

Fig. 133.

A, A. The punch P is about 5/8 in. thick at part T, and hollowed out the same as B to fit half section of the steel rod R. These tools may be fitted to either a hand or power press, and the face of P would slide up and down against face of B, in the position as shown in fig. 134, thereby forming an efficient form of chopping or shearing set of tools. Both punch and die may be made perfectly square, no bevel being required upon either.

Fig. 134.