The balance wheel should revolve away from the operator in Bradbury's No. 8 (Fig. 206) and in the Singer Left-hand Cylinder machines (Fig. 219). It should revolve toivards the user in Jones' improved (Fig. 205), Singer's I.M. (Fig. 213), Singer's Right-hand Cylinder, Singer's Buttonhole (Fig. 218), and Wheeler and Wilson's (Fig. 215). The wheel should turn from left to right as the hands of a clock in Thomas' circular head (Fig. 221) and Thomas' leather machine (Fig. 222).

Fig. 212.

The speed of running the machine is dependable upon whether it be a chain or lock-stitch; the kind of shuttle, reciprocating, oscillating, rotary hook, or rotary; and the tension, materials, and friction points. The finer the needle and thread, other things being equal, the higher the speed. The reciprocating shuttle machine may be driven up to 200, while the oscillating may be driven up to 300 per minute.

The average speed for leather work may be said to be from 200 to 350. Some of the special machines may be driven at a very much greater rate of speed.