The special stop motion used on these heavy presses is of a form particularly suitable for heavy work. It consists of a sliding block, reduced in the extent of its required motion by its surface being split up into divisions and corresponding projections, as shown by the following illustrations, figs. 172, 173, and 174. On referring to fig. 172 it will be noticed that when the block is at one end of its stroke the spaces 4, 5, and 6 in the lower block C are open to receive the projections 1, 2, and 3 on the upper box J, and the latter moves up and down without giving its motion to the slide (see figs. 172 and 173). But when the lower block is pushed in the direction of the arrow A, or right hand side of the slide, see fig. 174, then the projections on the box come on to those of the block, and the slide is thereby caused to descend. It will be understood that the more divisions there are in each block the less distance the block has to travel. This is important, since it reduces the time required to advance the block to a minimum, and in accord with the brief space of time allowed for it to properly engage. The projections are preferably made V-shape as shown by fig.

Fig. 173.

175. This greatly increases their sectional area to resist crushing and bending, and allows of a greater number of divisions, and therefore a less travel to be given to the block. This is a very great improvement, since it makes this kind of stop motion applicable not only to geared or slow-working press slides, but also to the slides of quick action presses, for the very important reason that in all high-speed presses it is desirable that when a stop motion is suddenly thrown into action it should be so arranged in relation to the moving parts that the motion be given to the least possible mass. This avoids the destructive effect of repeated blows on the parts composing the stop motion, and preserves a silence in the working of the press, which is a very desirable point when a large number of presses are working in one shop.

Fig. 174.

Fig 175.

Fig. 176.

In the case of a press having the stop motion in the flywheel, the latter going at 120 revolutions per minute, each time the stop motion engages into the crank shaft there is an unpleasant shock caused by the mass of the crank shaft, connecting rod, slide, and tools, having all to be thrown into instantaneous motion. An example of this type of stop motion is seen at fig. 176, where a sliding key is withdrawn by the extracting mechanism, operating upon the head of the key, as the flywheel is rotating. As the inertia of these parts is very great in heavy single-acting presses, it is obvious that the proper place to apply the stop motion in single-acting presses-especially in the medium and larger sizes-is in the slide of the press, rather than in the flywheel. Another patent form of stop motion more suitable for a single-acting press is the one shown at fig. 177. In this example the block is preferably circular, and a slight movement of the lever D is sufficient to start and stop the press. This motion may be arranged to be effected either by hand or treadle. The author has known a great deal of trouble to be caused by the continual hammering and knocking of the various types and shapes of claw clutches, often resulting in a very heavy cost for repairs in the case of quick running presses, besides frequently resulting in an operator loosing a finger, due to the sudden starting of a press slide. One form of stop motion referred to as being a dangerous method of stopping and starting, is that type seen at figs. 43 and 44, where a cast-iron clutch W C engages another claw clutch C, sliding along the crank shaft. A stop motion such as that described and illustrated, figs. 175 and 177-if either one or the other were introduced into the design of the four large power presses, figs. 46, 47, and 48-would allow of each press being worked separately with perfect success, and the tools could be set in any one press whilst the remaining three presses were at work. Such a stop motion has the following commendable advantages, viz.: It is positive in action; is in no way tricky or problematical, being easily understood; and it reduces the possibility of an unexpected descent of the slide to a minimum. The slide is of such small weight as to be readily balanced, thereby removing the liability of the crank and slide to suddenly descend in case it gets carried just over the crank shaft dead centre, as frequently occurs after the stop-motion key has disengaged in many of the American presses. In the case of small and medium size presses, the slide guide may be set up against the slide itself, sufficiently tight to prevent the slide from falling, when the stop motion is thrown out of gear, since the friction between the slide and slide guides would hold the slide at the top of the stroke, as seen in figs. 172 and 173. But for heavy slides it is much preferable to use balance weights, thereby removing any necessity of setting up the slide guides. In fact, it is safer, and much better practice, to work with a balanced slide even with the smaller presses. The Ryder forging machine, fig. 178, is used extensively for making bolts, joint pins, hurdle and fencing ends, and analogous work that require reducing or swaging quickly. This machine is made in a somewhat similar form as a power press, and may correctly be called a forging press. The speed is usually about 700 blows per minute, and the multiple slides allow a succession of tools to be used, each pair doing their part of the work. The back and front crossbars are used for fixing guides and gauges. The anvil of each hammer has a wedge adjustment that is used to determine the finished size of the article that is being forged; adjustment can also be made by the screw and hand wheels whilst the machine is in motion, and sometimes they are connected to a treadle, which can be operated by the workman's foot. This mode of working is to be preferred when the required reduction of the bar is considerable. A set of shearing tools are in the slide on the extreme right of the machine. A forging machine of this type is very useful for forging large quantities of press tools of any particular shape or dimensions. This is readily carried out by fixing suitable swaging and forging tools into the various slides of the machine. The metal shearing attachment, fig. 179, consists of a pair of 12 in. shear blades mounted in a light cast-iron holder, having the necessary adjusting gauges affixed. These may be readily added to any power press, thereby transforming the press into a cross-blade shearing machine. This fixture is very handy when material has to be cut up occasionally, and it may be made in all sizes to correspond with each size or type of power press.

Fig. 177.

Fig. 178.

The single-acting guillotine shears, fig. 180, are specially suitable for quickly catting iron or sheet metal into squares or strips; the stop-motion automatically disengages with the top blade, open ready for the insertion of the sheet. Its cutting speed is about ninety cuts per minute, if the treadle is held down continuously. The machine, as illustrated;at fig. 180, would cut sheets 48 in. wide by 1/8 in. thick. In the front table graduated rules are set for indicating the position 13wp of the front parallel gauge to cut any given size of sheet, andi the hack gauge has a parallel motion, also a taper adjustment for cutting off taper strips, if required. The connecting rods for working the upper blade arm are coupled to the blade by being engaged into recesses near the top of the upper blade arm, the other end of the connecting rods are attached to the crank shaft. This method of coupling to the top blade arm allows a much longer rod to be used than is usually seen on this kind of machine, and also avoids the tension coming upon a narrow section of cast iron, which is very liable to break, as is often the case when the connecting rods are coupled near the bottom of the blade arm.

Fig. 179.

Fig. 180.

Fig.181.

Fig. 181 represents a set of flattening or plate bending rolls, for dealing with large safe or bank doors, and similar work. After the plate has passed between the rolls, the motion of the top roll serves to carry it back ready to be put through again. The plate is first bent one way then the other. This process removes all indents, surface distortions, and unequal tensions, and by the adjustment of the parallel motion the plate can be either bent or flattened as required. The parallel motion for providing a uniform adjustment is very essential if good and expeditious work is required.

A set of circular cutting shears, used for shearing or cutting large blanks, are shown at fig. 182. In this example the cutters are started by a clutch motion, operated by foot. This allows the cutters to remain at rest whilst the sheet is adjusted, without any risk either to the operator or of spoiling the blank. The cutters are made with double cutting edges, and are accurately ground and hardened so that when one pair of edges have become dulled by continual wear, they can be reversed, the unused edges being brought into action. The lever grip for gripping the metal sheet acts instantaneously, and this method is preferable to the old screw type of adjustment. A graduated steel rule is fitted in the bed, so that the diameter of the blank to be cut can be readily determined, the adjustment of the rule being needed from time to time as the cutters are re-ground and the plane of either cutting edges are removed in relation to the zero on the graduated rule. The horseshoe grip is readily moved along the bed by rack and pinion motion, and the cutting head gauges so useful for metal splitting operations, can be affixed when desired.

Fig. 182.