It has been shown that large wheels are turned and bored while attached to disc-chucks, therefore for such wheels no arbor is required.

Whenever the wheels in progress are those having spoke-spaces large enough to admit bolts, the turning of the rims should be done while on the chuck, whether the wheels are small or large, because a chuck affords a firm support for the objects and prevents shaking; whereas a Avheel on an arbor is devoid of all support, except at the boss, where it is least required.

To properly turn a wheel by means of an arbor, the arbor must be carefully turned to fit along the entire length of the truly shaped hole in the wheel-boss, and should be as short as possible, with only length enough to allow room for the lathe-carriage. The shorter the arbor the greater will be the resistance to the cutting-tool, and the less will be the vibration. It is also necessary to rotate the wheel with two drivers in the chuck, one opposite the other. In order to yet further avoid vibration, the wheel is made to fit at one end of the arbor, so that while on the lathe-pivots the wheel is only a few inches from the disc-chuck. The two drivers are caused to bear against two of the wheel-arms, and between each arm and driver some pieces of leather, felt, or india-rubber are fixed, instead of allowing the two metals to be in direct contact.

In the event of a cog-wheel being turned, it is specially requisite to steady it during the turning, to prevent the teeth being suddenly jerked against the tool-edge, and either breaking the tool, roughing the surfaces being turned, or doing other mischief. To obtain the requisite regular onward movement, the drivers are fastened to the wheel-arms, and all backward motion thus prevented. This fastening is effected with poppets, if the arms present enough flat surface for the screw-points ; or with clamp-plates and bolts, if the arms are curved. Drivers are fastened also by tying them to the spokes with cord, and afterwards driving in one or two wedges to tighten the cord.