Testing Parallelism of Spindle Axis and Bed

Testing Parallelism of Spindle Axis and Bed

Testing Parallelism of Spindle Axis and Bed -

Checking Whether Spindle Axis is Parallel to the Bed

The dial gauge (G) is attached to the carriage (C) of the lathe and the mandrel (M) is fitted into the headstock spindle. The dial gauge plunger touches the surface of the mandrel near the end. To eliminate the effect of any out of truth of the mandrel, the spindle should be rotated slowly until the mean position is found.

After noting the dial gauge reading, the carriage is moved along towards the headstock (H) and the reading is taken at the other end of the mandrel (dial gauge shown dotted). These observations are made in both, the vertical and horizontal planes.

If the mandrel used is long, it may sag due to its own weight and may cause an error when testing in the vertical plane. To reduce this amount of sag, a hollow mandrel may be used. For a 300 mm swing lathe, the permissible inclination of the spindle axis relative to the bed should be less than 0.02 mm per 300 mm.