The advantage of the double-ended type of geared press, fig. 171, is that two presses are fixed and worked, occupying much less space than would be the case if two single presses were-used; further, they come out at much less cost in making. When there is a great quantity of repetition work, and not much tool changing required, then double-ended presses are, in point of first cost and working space required for them, a great advantage. The eccentrics are opposite each other, the cranks for working the slides being at 180 degrees, so that the strain of doing the work never comes on both together. The stop motion being in the slide is also a great advantage, and the slides being under independent control each can be stopped and started without interfering with the opposite end. Expert tool setters have been known to change the tools in one end of the press whilst the other end has been working. This has been frequently done in a similar press to the illustration, fig. 171, and by which means will be explained hereafter.

Fig. 171.

Fig. 172.

In presses of this kind for heavy work the slides are made of best crucible cast steel. This prevents breakage. In the case of fig. 171 there is a very ingenious and simple addition made to the packing plate adjustment. A top compensating screw allows any intermediate thickness of plate to be readily inserted, giving a convenience almost equal to a screw adjustment, so useful when using tools of variable length, and in the case of compressing or bending work. At the same time it reserves all the strength and solidity of the packing plate form of adjustment This is certainly the strongest known method of adjustment, but it is sometimes so constructed by some makers as to be incapable of fine adjustment. In the example referred to, fig. 171, the arrangement gives all the convenience that is desired. Further, the screw can be run back and will allow the slide to descend the top tool, entering into the bottom tool without fear of damage, because if the upper tool should catch in the lower tool it only rests there, indicating the movement needed to set the bed. The slides in these presses are so adjusted that their own weight causes them to descend as the screw is unscrewed, and the friction lever [_ is just tightened so that the slide is safely retained at any point of the stroke.