Third: The speed of the work in the lathe.
Fourth: The feed, or the thickness of the cut into the material.
Turning up a Cylinder.—The first and most important work is to turn up a small cylinder to a calipered dimension. When it is roughed down ready for the finish cut, set the tool so it will take off a sufficient amount to prevent the caliper from spanning it, and this will enable you to finish it off with emery paper, or allow another small cut to be taken.
Turning Grooves.—Then follow this up by turning in a variety of annular grooves of different depths and widths; and also V-shaped grooves, the latter to be performed by using both the longitudinal and transverse feeds. This will give you excellent practice in using both hands simultaneously.
The next step would be to turn out a bore and fit a mandrel into it. This will give you the opportunity to use the caliper to good advantage, and will test your capacity to use them for inside as well as for outside work
Discs.—A job that will also afford good exercise is to turn up a disc with a groove in its face, and then chuck and turn another disk with an annular rib on its face to fit into the groove. This requires delicacy of measurement with the inside as well as the outside calipers.
The groove should be cut first, and the measurement taken from that, as it is less difficult to handle and set the tool for the rib than for the groove.
Lathe Speeds.—Do not make the too common mistake of running the mandrel at high speeds in your initial tests. It is far better to use a slow speed, and take a heavy cut. This is good advice at all times, but it is particularly important with beginners