When programming the spindle indexing of a CNC lathe, we can use G code and M code to control the rotation of the spindle. The following is a simple example of spindle indexing programming:

1. Assume that we want the spindle to rotate 6 workpiece angles, each workpiece angle is 60 degrees.

2. First, we need to set the CNC system to rotary spindle mode. We can use M codes to achieve this. At the beginning of the program, add a programming code: M3 S1000 (start the spindle and set the speed to 1000rpm).

3. Next, we need to program the spindle indexing. Assume that the current X-axis and Z-axis positions are both zero. We can use G code and M code to complete this process. In the middle of the program, add the following programming code:

- G1 X0 Z0 (move the tool to the starting position of the workpiece)

- M0 (stop the spindle)

- G91 G1 X0 Z-60 (Move the tool 60 degrees in the X and Z directions in relative coordinate mode)

- M3 (restart the spindle)

- G4 P5 (pause for 5 seconds, waiting for the spindle to rotate into place)

- M0 (stop the spindle)

4. Repeat step 3 until all parts are completed. Please note that each time we move the tool, we need to stop the spindle and restart it after rotating it into position.

5. Finally, at the end of the program, add a programming code: M5 (stop the spindle).

This is a simple example of CNC lathe spindle indexing programming, for reference only. The specific programming method may vary depending on the lathe model, control system type and operation requirements. In actual operation, please make appropriate adjustments according to your own equipment and needs.