Fig. 1234.
An excellent method of chucking a pulley, and one that with care avoids the disadvantages mentioned in the foregoing methods, is shown in [Figs. 1232] and [1233]. It consists of a clamping dog, [Fig. 1234], that fastens to the lathe face plate, and secures the pulley by its arms, while supporting the rim and preventing it from chattering, if it is weak or slight.
This dog is bolted to the face plate by the two studs a and b. At c is a set screw for clamping the pulley arms against the screw d, and at f is a screw that steadies the pulley rim between the arms.
Cutting Screws in the Lathe with Slide Rest Tools.—In order to cut a thread in the lathe with a slide rest tool, it is necessary that the gear-wheels which transmit motion from the cone spindle to the feed screw shall be of the proportions necessary to give to the lathe carriage and slide rest sufficient lateral movement or traverse for lathe revolution to cut a thread of the desired pitch.
Suppose now that the feed screw makes a revolution in the same time that the cone spindle does, and it is evident that the thread cut by the slide rest tool will be of the same pitch as is the pitch of the lathe feed screw. If the feed screw gear-wheels of the lathe are what is called single geared (which means that no one stud in the change gearing carries more than one gear-wheel), it does not matter what are the sizes or how many teeth there are in the wheels used to convey or transmit motion from the cone spindle to the feed screw, for so long as the number of teeth on the cone spindle gear and that on the feed screw are equal, the feed screw will make one revolution in the same time as the cone spindle makes a revolution, and the cutting tool will travel a lateral distance equal to the pitch of the lead screw.
Fig. 1235.