Spindle Orientation

I'm Japanese and I'm not good at English. Posts use Google Translate, so please forgive me if it's hard to read.

Please tell me about the spindle orientation of the 3-axis milling machine.

With LinuxCNC + EtherCAT, XYZ uses a torque controlled servo amplifier.
The analog voltage is output by PID.
The main axis is a speed-controlled servo amplifier. use.
The speed from the Spindle is converted to analog voltage and output.
The spindle and servomotor are connected 1: 1 and the encoder of the motor is fed back to perform rigid tapping.

I want to orient the spindle, but I don't understand how to configure HAL. I also read a manual that uses orient to control with pid, but I think that the main axis cannot be used as it is for speed control.

I have a huge question. In the experience of old FANUC etc., there is no setting of the speed to rotate the spindle for orientation. In other words, even the speed setting for positioning is unknown.

Please give me some advice. Is there anything that needs to be done with torque control on the spindle?
Articles and materials with references are also fine.

Thank you very much.

Thank you, andypugh.

I rewrote the HAL with reference to the figure and executed it.
Spindle orientation is now working.
There are problems such as slow operation, but the result is satisfactory for the time being.

Since the servo amplifier of the spindle is used in the speed control mode, it does not seem to move smoothly, so I would like to consider how to handle it in torque control. It is an issue to consider because it needs to be changed from the wiring.

Thank you very much.