Now, supposing two such chucks and their rollers to be mounted on the lathe and rotated at a high speed, if the rivet B, fig. 118, be held perfectly central and firmly between the two chucks, and the chucks pressed up against the ends of the rivet B, the result will be that the rollers L, L will rotate in opposite directions, and a very light pressure will cause the rollers to spin over the ends of the rivet, thereby forming the heads H, H (see rivet A, fig. 118) where the rivet has been headed. This arrangement has been used extensively and successfully in connection with the manufacture of driving chains, in preference to riveting by means of either a hand hammer or power hammer.

Fig. 119.

Another example of spinning (see fig. 119) further illustrates what actually takes place during the operation of spinning sheet-metal articles by means of rollers in a lathe. A chuck M is mounted upon the spindle of a vertical drilling machine, and a pin P is driven through the chuck to carry the rollers R, R1. A steel cup C B, which has been previously drawn and pierced, is placed in the holder K, fig. 120, afterwards the holder and cup receives a cylindrical plug. The holder K is held by being fixed between the vice jaws

Fig. 120.

(see fig. 120). The cup C B has a curved end, and is exactly the shape that it would be when it leaves the cupping tools (see fig. 121).

Now, having secured the cup C B, the plug and the holder K all in the vice, so that the centre of the cup C B stands directly under the centre of rolls R, R1, if the spindle and chuck are rotated, and the rolls R, R brought down upon the end of the cup, they will roll in opposite directions, and roll or spin the end of the cup perfectly flat, as seen at CA, fig. 119. The cylindrical plug A forms the anvil, and the curve on the end of this plug governs the inside shape of the cup. 9wp

Fig. 122 is a useful and cheap form of chuck, which may be made of either cast or wrought iron, and used for chucking cups of this kind to enable them to be operated upon by turning tools in a lathe. A section of the chuck is given, from which its form will readily be seen. After being screw-cut at N to fit any lathe spindle, it is bored out at L to receive the cup CA; it is also counter-bored as large as possible (consistent with strength) in the centre of its length to ensure of the chuck springing at T when under pressure of the pin collar C of the pin P. A hole V is drilled at right angles to the pin hole, a slot S being afterwards sawn from the front of the chuck into the hole V. The fact of the metal chuck being comparatively thin at T, assisted by the hole being drilled at V, ensures sufficient springing of the chuck under the pressure of the pin P to firmly grip the cup C A. Chucks of this type may be quickly altered by re-boring to accommodate a new size of cup, or they may be completely faced off at the front end when worn down and be again re-bored to suit a smaller-sized article.

Fig. l21.

The process of building up a roller-chain link having separate bosses will serve as an example to show how the extracting mechanism may be actuated by the slide of a power press; at the same time the usefulness of the power press, as a means of reducing the cost of production, may be seen from this operation.

Fig. 122.

Fig. 123.

Referring to fig. 123, it is required that the blank A shall have the metal so cut away from one side as to form two small bosses. To do this the blank is first pierced, it is then fixed upon two pegs in a lathe, whilst a special milling cutter is brought up against one of its sides to remove the metal from the centre (see fig. 123 at B). Finally, another smaller milling cutter forms the two bosses separately, to complete the bosses as seen at C. From this it will be evident that to make large quantities of similar plates would, in addition to being a great waste of metal in forming the bosses, necessitate a large number of small milling lathes being employed for the operations, besides using up quantities of cutters. It was to overcome these difficulties and to make the production cheaper that the tools seen at fig. 124 were introduced. Passing to fig. 125, another blank A is seen, this time cut from metal of suitable thickness as required for the finished article. The blank has two holes pierced in it, equal in diameter to the outside diameter of the required bosses. Two pieces of cylindrical steel E, E are cut off a bright rod, and forced into the blank A. The next operation will be to use the tools as seen at fig. 124 to 127. These tools are fitted in a heavy double sided power press. The construction of the punch holder, die and die holder, or the methods of holding the punches and dies needs no explanation, these having been previously described in chapter 8.

Referring to fig. 124, a slot is planed straight across the bolster K, to receive the square piece of steel H, and when H is allowed to fall so as to reach the bottom of the slot the two steel pegs E, E are pushed down the holes of the dies. These steel pegs E, E are of such length that when one end rests upon the top of H the other end stands below the top of the die. The correct distance that E stands below the top of die is a little less than the length of the boss E on the blank B, fig. 125. From this it will be evident, by referring to figs. 124, 126, and 127 that when H, E, E are in their lowest position the two bosses E, E could be dropped into the holes of the die, leaving the blank on the top just clear of the die. The press is next moved through one revolution of its crank shaft, during which time one down stroke and one up stroke are made: on the down stroke centre punches P, P will punch the centre holes 0, 0 of the blank B, fig 125. The process of punching these centre holes will expand the small bushes E, E, fixing; them very firmly in their respective holes in the blank.