Back or front tool

I have the 160TCL and had the same issue with switching the spindle DC motor direction with M3 & M4. It was easily resolved with a polarity reversing module which I bought from a model railway supplier.

I can have a look at how I did it and send you the .hal example if you are interested?

Thanks Rider and and yes please .
I think I have the kit to actually reverse the polarity . I have been doing it manually with a 2 pole changeover switch and have set up a relay to do the same . I think I just need the hal entries to make a chosen pin operate one of the relays on a small board which in turn will energise my reversing relay,
Still interested to see your setup as well though.

linuxcnc.org/docs/2.8/html/man/man9/moti....html#SPINDLE%20PINS

spindle.0.reverse - TRUE when the spindle should rotate backward

Fine but is that all that i need to add to my hal .
Somehow I suspect not
Please remember Andy that I am a novice here
My Hal was generated by initially by stepconfig and although I have progressively added a number of functions I have not needed to alter the spindle commands so i am floundering here !

Which output pin (if any) is connected to your reversing relay?

Is it safe to reverse with the spindle on?

Was planning for 14 or 16 unless you advise otherwise
Would not be safe to call for M4 if spindle running under M3 and Vice versa .
Was planning to call for a pause but if that can automated then all the better