Lathe IX – Taper Calculations and Machining

The amount a job differs in diameter or height from the large to the small diameter or end is known as the taper.

When cutting tapers you must often use formulas to determine sizes and machine settings. The formula sheet which you have has the formulas which you will need.

Moving the tailstock or offsetting the tailstock is one of the methods used to cut a long taper. Before setting up you must calculate how much to move the tailstock.

Using this information you could then mount a dial indicator with magnetic base on the ways, with the plunger touching the tailstock spindle horizontally, use the two tailstock setscrews to shift the upper half of the tailstock.

Some engine lathes are also equipped with taper turning attachments.

Telescopic taper attachment

When a plain attachment is used, the binding screw which connects the cross-slide to the crossfeed screw nut must be removed. The screw is then used to connect the sliding block and the slide extension of the cross slide. You have to use the compound rest handle to set the depth of cut.

When using a telescopic taper attachment you will only have to tighten the clamping bracket (D) instead of moving the screw. The depth of cut is made using the crossfeed handle, since the cross slide and crossfeed nut are not disengaged.

Settings on the attachment can be in taper per foot graduations or in degrees

Short taper can be cut using the compound rest Short taper can be cut using the compound rest. The amount of travel the compound rest has dictates the length of taper that can be cut.

At this point it would be helpful to go back and review pages 100-101 to help us with taper calculations and how to check a taper using a 5 inch sine bar.