Fig. 189.

Fig. 190.

It is possible to adapt one dial-plate to a variety of work by making the holes in the plate slightly larger than the largest sized article to be dealt with, then fixing bushes into each hole of the dial-plate, of suitable shape to receive the articles to be pierced, bent, or cupped, as the case may be. It is, however, much cheaper and less trouble to the operator to have a separate top dial-plate for each size and shaped article to be handled, for since the complete dial-feed motion is already attached to the machine, the only renewals required for dealing with new shaped blanks would be additional dial-plates. If all the blanks passing through the machine are round blanks, and of many different sizes, it may be advisable to use bushes in the dial-plates for the smaller sizes, since bushes for round work can be made considerably cheaper than for irregular shaped articles. It is necessary to have the holes in the dial-plates slightly larger than the diameter of the blank to be pierced, so as to allow for expansion, otherwise the blanks might stick in the holes instead of being drawn out by the punch and cause trouble or breakage of tools. If the holes in dial-plate are made sufficiently large the punch will then lift the blank from the hole in the dial-plate, and it will then be drawn off the punch by means of a releaser or stripper. In this case it is essential for the press to be inclined, to allow the work to fall from between the releaser and dial-plate, the blank dropping into a box at the back of the press. When the dial-leed is used for cupping or re-drawing it is also advisable to make the holes sufficiently large in the dial-plate to allow the blank or cup (as the case may be) to fall freely into position on to the die, ready to receive the cupping or redrawing punch.

Fig. 191.

Fig. 192.

The adjustable double action power press, fig. 192, is fitted with a set of automatic feed-rollers. This machine is largely used in the manufacturing of bedstead knobs and similar light brass work. It is fitted with treadle clutch motion, enabling the operator to stop the machine instantly if required, and, being an adjustable machine, it can be worked on the upright or incline position, which is of considerable advantage. Since the machine can be worked up to 125 strokes per minute, and both cuts out the blank and forms the shell to shape at each descent of the ram, it follows that the output is large and the cost of manufacture reduced to a minimum.

A double-action press of somewhat different design is shown at fig. 193. This machine is designed for the same purpose as the previous one, but is fitted with a double set of automatic feed-rolls for more accurately passing on the sheets and reducing the amount of scrap to a minimum. This method of working the feed-rolls is a substantial one, the arm that actuates the rollers being manipulated by a separate slide from the crank shaft end. For operations which do not entail the necessity of these feed-rollers an arrangement is provided on the bed of the machine by means of which the rollers can be swivelled out of the way of the operator.

A power press of strong design is seen at fig. 194, fitted with feed-rolls for use when cutting out round or irregular shaped blanks from strips of sheet metal drawn automatically through the rolls. The rolls may at any time be readily removed, and the press made available for general cutting out and shallow drawing. The machine is fitted with patent positive stop action or clutch, as desired.

The machine, fig. 195, is an adjustable power-press of simple, strong, and serviceable design, and is used extensively in the manufacture of sheet-metal ware for working the dies in cutting and stamping covers and bottoms of a canister at one operation, and also for cutting body-blanks,[piercing, embossing, and similar purposes. It is fitted with a treadle clutch motion of novel design. An additional attachment known as a finger guard is frequently added to this class of machine, and it is claimed that whilst practically preventing accidents to the operators' fingers, it also serves the purpose of stripping the tin off the top punch. The clutch 14wp motion arrangement can be clearly seen in figs. 196 to 198. We may repeat that the chief cause of the loss of limbs in working a power-press is the unexpected second descent of the ram when it is not intended or expected. Many types of clutch motions are unreliable and accidents will occur with them, even if the greatest care is exercised. The safety-clutch, however, represented in figs. 196 to 198 appears to offer advantages worthy of notice. The following explanation will enable its action to be readily understood: When the treadle-rod is depressed the"knock-off"C, is thrown into an angular position, releasing the clutch and causing the ram to make a down stroke. Before the crank has completed its revolution the small roller A strikes the piston B, releasing the"knock-off"C from the treadle-rod The"knock-off"is then instantly thrown back to its original upright position (by means of a compression spring) in ample time to prevent a second descent of the ram.

Fig. 195.

Fig. 196.

Fig. 197.

Fig. 198.

Referring to fig. 195, it will be noticed that the ram is coupled to the crank shaft in a manner which enables lengthy adjustments to be made. A sectional view is seen at fig. 199, which explains itself. Another useful design of counecting-rod, shown at fig. 200, is suitable for presses in which it is desired to bring the ram as close up to the crank shaft as possible, as is the case with small presses of simple design, the adjusting-rod is coupled to the mm by a ball joint, and when this is carefully fitted, it is a great success and works with very little friction. In some designs the screw instead of having a lock nut as shown, is secured by a set pin screwed into the side of the strap rod against a suitable packing-bit, arranged to firmly hold the screw in position without damaging its thread.

Fig. 199.

Fig. 200.