Mandrel or Arbor Press.—The best method of inserting an arbor of the solid type in a hole is by using a press, [Fig. 18], designed for that purpose, but if such a press is not available and it is necessary to drive the mandrel in, a “soft” hammer, made of copper, lead or other soft material, should be used to protect the centered end of the arbor. In either case, the arbor should not be forced in too tightly, for if it fits properly, this will not be necessary in order to hold the work securely. On the other hand, the work might easily be broken by attempting to force the arbor in as far and as tightly as possible. In using the arbor press, the work is placed on the base B with the hole in a vertical position, and the arbor (which should be oiled slightly) is forced down into it by ram R, operated by lever L. Slots are provided in the base, as shown, so that the end of the arbor can come through at the bottom of the hole. The lever of this particular press is counter-weighted so that it rises to a vertical position when released. The ram can then be adjusted quickly to any required height by the handwheel seen at the left.
Some shops are equipped with power-driven mandrel or arbor presses. This type is particularly desirable for large work, owing to the greater pressure required for inserting mandrels that are comparatively large in diameter. One well-known type of power press is driven by a belt, and the downward pressure of the ram is controlled by a handwheel. The ram is raised or lowered by turning this handwheel in one direction or the other, and a gage shows how much pressure is being applied. This type of press can also be used for other purposes, such as forcing bushings or pins into or out of holes, bending or straightening parts, or for similar work.
Fig. 19. Steadyrest and Follow-rest for Supporting Flexible Parts
Steadyrest for Supporting Flexible Parts.—Occasionally long slender shafts, rods, etc., which have to be turned, are so flexible that it is necessary to support them at some point between the lathe centers. An attachment for the lathe known as a steadyrest is often used for this purpose. A steadyrest is composed of a frame containing three jaws J ([Fig. 19]), that can be adjusted in or out radially by turning screws S. The frame is hinged at h, thus allowing the upper half to be swung back (as shown by the dotted lines) for inserting or removing the work. The bolt-clamp c holds the hinged part in the closed position. The base of the frame has V-grooves in it that fit the ways of the lathe bed. When the steadyrest is in use, it is secured to the bed by clamp C, and the jaws J are set in against the work, thus supporting or steadying it during the turning operation. The steadyrest must, of course, be located at a point where it will not interfere with the turning tool.
