It is evident on the component below that several tools will be needed to machine the B-axis features. On most machines a move to toolchange cancels the index position, resetting the datum to the turn origin. Therefore after calling up the next tool the index position has to be reapplied.
Using the Maintain Index option on the tool change command dialog forces an index move back to the previous index position. This saves you having to perform a separate command to index back to the CPL after each toolchange.
The Maintain Index check box only appears on the tool change dialog after an index command has been previously performed.
Upon selecting a turning tool or any static cutter the datum is automatically reset to the turn datum.
If Maintain Index is specified following a rotary rotate the C-axis is repositioned back to the C orientation of the original CPL.