> Exactly what I'm doing.  Except no endoder, stepper driven and likely
> needs a bigger motor, and more speed reduction to improve the holding
> power.  Thats a downright puny motor on it now, and I have a 270 oz/in
> currently holding down a stepladder step. 8 wire so slower top speed but
> easy on the psu. In fact I think I'll check and see if its shaft is
> compatible yet today.

I just tried an experiment with my CNC router which is MACH3 driven.  I set up 
a spare input on parallel port 2 to be the Home switch input for the A axis.  
The rotary axis is a small 4" rotary indexer driven by a small stepper.

With the home set not activated I do a ref all home which sends each axis home 
in the following order.  First the router is moved up to the top limit/home 
switch.  Then the Y axis is moved towards me to the limit/home switch.  Then 
the router carriage is moved to the left until it reaches the limit/home 
switch.  Finally the rotary indexer starts turning and stops when I activate 
the switch.  Then it moves back in the other direction until I deactivate the 

That's behaviour as expected.

Now I move the rotary axis away from my 0 position to 60 degrees.  Move all the 
other axis away from their home.  Then do a ref all home again. Like before, Z 
first, then Y and X, finally it wants to move A but it can't.  Instead I get a 
message that the Home switch is already active and that I should move it off 
the switch first.  That completes the homing cycle.

The A axis is still usable.  I can manually set A to 0.0000 by clicking a 
button on the screen.   I can enter in a G0 and then an A5 and see the rotary 
axis move to 5 degrees.

So even if I had a switch for an A axis home, all I get is a warning that the 
switch is activated and fix it.  It doesn't seem to cause any other problems.  
So I can run my CNC router with or without the A axis connected.  As long as 
the switch is open (NC home switch).

I would guess there must be a similar operation for LinuxCNC.  I can't test 
that until I put the big system back together and swap the hard drive for the 
LinuxCNC version.  (Should really make this dual boot but that's a different 

So perhaps play with your switch polarity (NC verses NO for Home Sensing) and 
see if you can make that work.


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