HEIDENHAIN TNC 640 (34059x-02) ISO programming - Manual (Page 453)

Spindle speed S, feed rate F and miscellaneous function M 15.3
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TNC 640 | User's Manual for DIN/ISO Programming | 5/2013
453
Adjusting spindle speed and feed rate
With the override knobs you can vary the spindle speed S and feed
rate F from 0% to 150% of the set value.
The override knob for spindle speed is only functional
on machines with infinitely variable spindle drive.
Activating feed-rate limitation
The feed-rate limit depends on the machine.
Refer to your machine manual.
When the F LIMITED soft key is set to ON, the TNC limits the
maximum permissible axis speed to the safely limited speed
specified by the machine manufacturer.
Select the Manual Operation mode
Scroll to the last soft-key row
Switch on/off feed rate limit