The thickness of steel piece B determines the centres of the punches, since the holes for receiving them are drilled at the point where the faces of A, B, and C come together. After the punch holes have been drilled in steel pieces A, B, and C a little would be filed off the faces F 1, F 2, F 3, F 4 (see fig. 99). This would enable the pieces A, B, and C to firmly grip together the punches, when the set screws shown at fig. 95 are screwed up firmly. A plan and inverted plan of the punch holder is seen at fig, 97. The clearance holes C, H are to allow the punch holder to come down close to the stripper plate, and in doing so to clear the nuts of the stripper holts N, fig. 101. Unless these holes were drilled in the punch holder it would he necessary to let the piercing punches stand out further, probably causing them to spring during working. The guide plate V 1, fig. 98, guides the blank and holds it in position whilst it is being pierced. P 2 is a packing plate, and P 3 is another plate, which has a slot in it to receive a small tongue piece and spring, and is known as the knock-out or flipper, their office being to extract and throw the blank from the tools after it has been pierced. The plate P 4 serves the double purpose of guiding the piercing punches and stripping the blank from the punches after it has been pierced. The four plates PI, P 2, P 3, and P 4 are all bolted to the top of the die holder in the order of their numbers, thereby forming a complete set for holding, piercing, stripping, and extracting the blank from the tools. The author's object in giving the chain link as an example of cutting and piercing, is that he considers it to be a class of work requiring exceedingly accurate workmanship. It therefore forms a good specimen for the student to investigate, and on several of the sketches are given the actual working dimensions, thereby enabling the student to use them as a guide in designing similar tools to be applied for other purposes than the chain link blank.

Fig. 95.

Flo. 96.

Fig. 87.

Fig. 98.

Fig 99.

Fig. 100.

Fig. 101.

A complete set of tools for cutting out a chain link are shown in figs. 102 to 106. The combined die holder B receives the die D, which is keyed in position by K, the strip of metal from which the blanks are cut being fed into the tools by the feed rolls R, R. The making of these punches and dies has been explained in reference to figs. 90 and 94. The combined metal guide and stripper, figs. 104 and 105, is fixed upon the bolster by the double-screwed pins, one of which is seen at fig. 104. The short end of these pins is screwed into the holes A, A of the die holder B (see fig. 103), and the stripper plate can be raised or lowered at will over the top of the die D by means of the two lock nuts (see fig. 8\vp

Fig. 102.

Fig. 103.

104). G, G are the guides shown on the inverted plan. Reference to this useful type of combined guide and stripper arrangement will be made in a subsequent chapter on tool setting.

Fig. 104.

Another interesting example of the use of steel bushes for accurate production is the drilling of a small chain block of figure 8 section. The tools for this operation are seen in detail, figs. 106 to 110. The centres of the holes to be drilled in the block are .4 in., and these centres are obtained by means of the small steel bushes. The centres may be reduced or increased by a method which will be explained in another chapter. Referring to fig. 106, a plan C, a side elevation B, and an inverted plan A of the complete jig are seen. The block to be drilled is held firmly by the thrust from the end of slide S, which is screwed up by the handle H. At fig. 107 the jig is seen in position upon the table T of a vertical sensitive drilling machine, ready to receive the drill through the jig bushes. The drill is held in the drill chuck D C by a very simple and reliable means. It may here be mentioned that in the case of the ordinary and well-known types of self-centreing chucks, as used by tool makers and machinists, two and sometimes three jaws are brought together by small screws. Although these are very useful and reliable when in the hands of skilled mechanics, they may become a source of trouble and expense when in the hands of unskilled labour. There are instances where unskilled labour have the setting of their own drills, and where the required rate of cutting makes it very essential that the drill be gripped very firmly on account of the rapid-cutting action of the drill, tending to cause the drill to rotate in its own chuck. This necessitates a strong, cheap, and reliable chuck being placed into the hands of the operator. Such a chuck is seen at fig. 108, where the drill is received into a long bush B, having one side cut awayafter it has been drilled-to receive a separate piece K. The set-pin for gripping up the drill is brought against the back of K, there being a flat filed upon K to receive the thrust from the end of the pin. This form of chuck will stand a great amount of rough usage without getting out of order. Fig. 109 is the guide-thrust plate, used for setting the block into position. The plate is first drilled, as shown, afterwards being shaped away to fit the shape of the block (see F, fig. 109). The thrust slide S of this drilling jig is shown at fig. 110, there being three views: a side elevation S 1, an inverted plan or view of bottom 1 P, and a plan or top view P.

Fig. 105.

Fig. 106.

Fig. 107.

Fig. 108.

Fig. 100.

An example of wire-working tools, as showing the application of the punch and die for such work, is seen in fig. 111. The complete set of punches and dies are shown for automatically flattening, double piercing, and cropping or cutting off an umbrella stretcher. The wire at the top of the drawing gives the four stages A, B, C, D in the progress of the work. The wire is fed through the machine by means of a grip-feed, which is worked by a crank and connecting rod. The stroke of this crank can be varied at will, and the length of stroke given by the crank will determine the length of the finished stretcher. The blocks or castings carrying the tool slides, into which the various tools, punches, and dies are fixed, are necessarily set a certain distance apart, suitable packing pieces being used to give the required distance. To deal with each length of stretcher that is being made on the machine the plate-iron packing pieces are dropped between each set of slide blocks. The four sets of slides are worked by levers and rollers; they are connected to act at the bottom of the slides, and are actuated by means of cams and cam shaft working under the bed of the machine. Beginning at the right hand side of the drawing, fig. 111, the flattening punches are seen at A. They are ground upon their ends to produce the flattened shape seen on either side of the wire. The second and third set of tools are the two sets of piercing tools. Each die is backed up by a long set pin, which is used for setting up the dies, a hole being drilled through the centre of the pin, through which the piercing bits pass and drop into an iron box. The fourth and last set are the cropping tools. The cropping punch is shaped upon the end to the exact shape necessary to remove the bit of scrap to form the two ends of the stretcher. The cropping die is of peculiar and novel construction. It is formed or built up by placing two pieces of round steel at a certain angle so that when they are moved forward by the set pins at their back ends the distance between their cutting ends will be reduced. This may sometimes be necessary, should it be desired to make the punch and die a better fit. The cropping punch, when being made, can first be roughed out, then put into the machine, and carefully worked up against the cropping die so that the two pieces of round steel which form the die would gradually cut away the end of the punch into the required shape.

Fig. 110.

Upon the extreme left of the drawing, fig. 111, the end views of the four sets of tools are seen. A very neat arrangement is here shown for fixing and adjusting the small piercing punches. A taper hole is bored in one end of the slide, and in the other end a larger hole is drilled and tappet! to receive the punch-holder. The holder is bored for a portion of its length to receive the piercing punch. A clearance hole is then put in for the remainder of its length to receive a long thrust rod, and finally the back end of the holder is tapped to receive the backing-up set pin S P, after which the punch holder is sawn along one side of its taper end, as seen in the end view. From this it will be readily understood that if P H be unscrewed, say half a revolution, this liberates the piercing punch. The lock nut L N can now be loosened, and the punch advanced as required to enter the die by means of the backing-up pin S P, after which LP can be locked again, and finally the punch holder P H can be screwed into position, thereby forcing the taper end of the punch holder into the taper hole of the slide, and closing the ends of the punch holders firmly upon their respective punches. All four sets of tools ran readily be adjusted whilst the machine is in operation.

Fig. 111.