Sorry out of my depth but have a look at this
http://www.cnczone.com/forums/stepper_motors_drives/112753-wiring_two_stepper_motors_single_controller.html

Jim

Hi Gary,

Assuming I understood your description correctly this is how I arrived at the figures…

Your steppers are 200 steps per revolution – that is 1.8 degrees per step.

When you set 1/8 micro-stepping (8 micro-steps per 1.8 degree step) this increases the steps per revolution to 1600.

You have a gear reduction of 20 tooth to 60 tooth which equates to reduction of 3:1

You have a 20 tooth pinion running on a 1.5mm pitch rack so one revolution of the pinion moves it 30mm along the rack. This makes the equivalent lead-screw pitch 30mm.

Tweakie.

Hi Gary,

Slaving the X and A axes.

As said, I am not an expert at this because I have never had occasion to actually do it but…

In Motor Tuning make the settings exactly the same for both the X and A axes and save the settings for each.
In General Config uncheck the A-Axis so it makes the A axis Linear.
In Slave Axis select X to A then restart Mach3.

You should now have both these axes slaved.

Tweakie.

Hi Tweakie
You're bloody wonderful! You sure as heck cleared the mud from my eyes.
I got to grips with the 200 steps (360/1.
I was battling with the micro stepping, in other words..... how to translate one eighth into a an understandable figure. If my understanding is correct: 1=full step; 1/2=2microsteps/1.8deg step, 1/8=8 microsteps/1.8deg.step, 1/16 =16 micro steps/ 1.8deg step.
The gear ratio, I understood, but you certainly put me o track with the leadscrew pitch.
Can I interpret the 1/2"-10, 5 start  acme screw's lead screw pitch (mcmaster-carr says 1/2" travel per turn) into metric format namely 12.7mm per turn.

To get back to the subject of slaving one axis to another.
direct quote from another source:
"In Mach, go to config->ports and pins->motor outputs.  Change the check mark or x in the "Dir LowActive" column so it is opposite between X and the slaved A axis.  This will cause the motors to be slaved together, but to rotate in opposite directions, which is required since they are mirrored in position to one another."

I would appreciate a comment on this before trying it out.
Regards
Gary

bloody smiley popped into my text should read 360/1.8deg

To get back to the subject of slaving one axis to another.
direct quote from another source:
"In Mach, go to config->ports and pins->motor outputs.  Change the check mark or x in the "Dir LowActive" column so it is opposite between X and the slaved A axis.  This will cause the motors to be slaved together, but to rotate in opposite directions, which is required since they are mirrored in position to one another."

If the motors are indeed 'mirrored in position', (which is likely for a rack and pinion setup) then 'yes'.

Can I interpret the 1/2"-10, 5 start  acme screw's lead screw pitch (mcmaster-carr says 1/2" travel per turn) into metric format namely 12.7mm per turn.

Yes.

Tweakie.

Hi Tweakie
Seem to have my problems sorted for now. The motors turn and get decent movement on all axis. The cable seems to have been the cause of all my woes.
Once the pin to pin wiring was sorted on the cable I had made up,its length seemed to be an issue (3m cable made up). Having switched back to the cable I had loaned I was able to tune the motors to get them to run relatively decently. I still have some minor parts to make and install on the table (cable trays,spindle mount and the likes). I am now busy with fine tuning and calibrating the axis while the parts are being  laser cut.
The main issue with these boards, seem to be the poor instructions/manual that is supplied, together with the different variations available.
I have found that I did not have to "oppose" the dir low active setting (motor outputs) for the 2nd side of the slaved axis to get it to run in the same direction (A slaved to X).
All that seems to determined is the test of time, regarding the longevity of the board.
Regards
Gary
 

I am pleased you are getting it sorted Gary and that it is all starting to take shape. 

Tweakie.