The particular sphere of the turret lathe, and the use of the various tools and tool-holding devices, can be best explained by illustrating and describing some of the more important operations in the machining of castings of the usual forms.

Some of the practical observations applicable to the handling of the work and the tools are given, and their importance should be fully realized by the novice in attempting turret-lathe work.

Great care should be used to have all tools, tool-holders, attachments, fixtures, etc., securely clamped in place, so that there will be no danger of their working loose, and vibration will be eliminated as far as possible.

The tools should be ground to the correct shape, and the finishing tools should be carefully stoned with a fine-grained oil-stone so that their cutting edges will be smooth and keen. They will then do much smoother work, and the cutting edges will last much longer.

Generally there must be a roughing and a finishing cut, the same as in an ordinary lathe. In the turret lathe the two cuts are made by different tools, so as to avoid constant changes of adjustment.

Stop-gages should be carefully set so that correct dimensions may be produced when the turret slide or cross-slide, as the case may be, is run firmly against the stop, but so that there is no straining or forcing of it. Unless care is used in this respect, correct dimensions cannot be maintained.

Proper speeds must be used, according to the material to be machined and the diameter of the work. The same speeds will be used as for engine lathes. When tapping or threading dies are used, the speed, on the cut, must be very materially reduced.

In chucking comparatively thin cylindrical work, it should be held by the outside, as there is much less danger of breaking it than if it is held by the inside.

In machining heavy-rimmed balance wheels, they are frequently held by the inside of the rim so as to leave the outside and face clear for the tools.

Pulleys and similar light wheels are frequently held by the arms, which rest against suitable supports so as to avoid distortion and to leave the rims and hub free for machining operations.

In boring operations, particularly deep holes, the tool should be made with a long guiding end or pilot, which may enter a bushing in the main spindle of the machine before the tool commences to cut. This will reduce vibration and chatter, insure a true hole, and prolong the life of the tool.

When the piece of work is comparatively long-that is, projects to a considerable distance from the chuck-the outer end should be run in a center rest similar to that on an engine lathe, to hold it true and rigid, and to insure true and accurate work.

Fig. 309. Turret Lathe Arranged to Machine Webbed Balance Wheel.

Fig. 309 is a plan of the chucking arrangement; the turret and its tools; and the cross-slide tool-block of a turret lathe arranged to machine a webbed balance-wheel. It is to be finished all over, and must therefore require two operations.