Large wheels are frequently both bored and partly turned with one chucking, or, as it is termed, one setting-up, for each wheel. Some sorts of wheels, such as a grooved wheel for a foot-lathe, can be entirely completed with only one fixing, because only the hole and one side of the wheel are operated upon, the other side remaining as it was when cast.

A cog-wheel of two, three, or more feet in diameter, having spokes, is turned and bored as stated, with only one chucking, and is fastened to the chuck with plates across the spokes, and poppets in the spoke-spaces, so that the screw-points shall bite the inner side of the rim. For the fixing of a wheel of this class parallel blocks are put at the proper places on the chuck to suit the size of the wheel, and are usually put into contact with the rim, unless it is specially desirable to turn and bore the wheel square to the arms rather than to the rim.

The holdfast plates employed to hold the wheel should be slot-plates, which allow the screw-bolts to be easily put at any required place along the slot to suit the holes or slots in the discchuck. The paws of the plates are to be put near the inner part of the wheel's rim, upon the junctions of the arms, and this arrangement will allow the front side of the rim to be turned, and also the outer surfaces of all the teeth, the wheel's rim being at the same time firmly held and its tendency to tremble greatly mitigated.

After the wheel is adjusted for placing its rim concentric with the chuck, it is in position for turning. But, previous to commencing, the boss must be supported to keep it steady and afford great resistance to the cutting-tool, and to avoid the risk of breaking the spokes. For this purpose smooth hard wood packing-blocks are pushed in behind the junctions of the arms with

2x2 the boss, and also in contact with the boss itself, if large enough. Both parallel blocks and those that are slightly taper, are used, and are driven in only tight enough to remain in position without distorting the wheel.

The turning and boring can now be safely done, and the cogs will be true with the hole when turned, supposing that the wheel does not shift during the process, or bend in some part, which it is likely to do, especially if it is several feet in diameter. To avoid trouble that may result from such occurrences, it is proper to first roughly bore the hole, and turn the boss to near its finished size, and next turn the rim and teeth. These parts can be now entirely finished, after which the boss is to be smoothly finished, and its hole finally enlarged to the exact diameter by removing very thin slices with a sharp tool.

A circular line can also be marked, if necessary, upon the rim at the intended bottoms of all the teeth-gaps, the line being required as a gauge-line during shaping.

The outer circumference of the wheel and one side of the rim are now completed, also the hole and one end of the boss, all these surfaces being true with each other; consequently the wheel can be next reversed, the side which is not turned being now put outwards, and the turned surfaces of the teeth put against the parallel blocks, in which condition it is again adjusted to execute what little further turning may be requisite.