I would be interested to see some pics of your mill.
Have you tried typing zero into the DROs?
Hood

You can't type zero in machine coords DROs.

oh sorry should have read what you were wanting
Hood

Ok you said you press the zero button to put the DRO to zero, what zero button is this?

Hood

I built my own screen set. On it I have buttons utilizing SetMachZero(). You can use (0),(1),(2),(3),(4) which refer to x,y,z,a,b. This function zero's the machine coord for the particular axis. IMO it isn't working as it should. I understand the dilemma with the steps per unit, but disagree with the only solution being to say I need to fins a means of increasing my steps per unit.

Image teaching this software to a new user. You have a button that says "ZERO MACHINE COORDINATE AXIS" and now you need to explain to them that it doesn't really zero because of the steps per unit is not allowing it to achieve the true position of zero cause its inbetween microsteps. They look at you crosseyes like you have 3 heads and they are asking what do you mean steps, what resolution, doesn't the machine just do what I say.

It's like this: where ever my machine is now I want it to be zero now. The machine doesn't need to move or calculate or anything just make my current position machine zero. 
I know you really only need this when you have homing switches so as to reference, which is what I do, but I'd like to use this function and the way I see it it doesn't work. I'm not understanding why that is an issue. Please educate me.

Your button is a custom button? If so I presume it is a VB button? If not what OEM code does it have?
Please educate me why you would need to set machine coords zero at the position you are currently at, I would think most people would just use a work offset but maybe I am not understanding.
Hood

(;-) You cannot SET the "machine coor" except at startup or Home. It is Machs internal place keeping system and it is good to about 10 places or so beyond the decimal point.

Machs "user" coor system is based on the steps per unit resolution as compared to the Machine coor base. SOmetimes at the EXTREME side mach has to resolve the conflict of the position requested is smaller than the smallest step and does so accurately.

Very few people try to run there machine at such EXtreme resolution as you are trying.

You also cannot expect the machine to be able to display the absolute zero without providing the correct Steps per rev to do so.

You are attempting a resolution that most humans cannot even measure (;-)  WHat are the +/- tolerances that you need to work in??

Perhaps you need to set the dros to display a lesser resolution so you will not be able to see mach resolving the steps issue.

(;-) TP

"My machine is mechanically plenty capable of making 0.0013mm moves" - Unless my calculator is broken, that is 0.00005", or 50 *millionths* of an inch.  Perhaps your machine, on paper, has that kind of resolution, but I would be surprised if it has that kind of *accuracy* in the real world, unless you're running in a very tightly temperature-controlled environment.  As you said the microstep precision alone is nowhere near that good.  And, I doubt you have any means of measuring to anywhere near that kind of resolution.  Resolution without accuracy is not good for much other than bragging rights.  Unless I'm missing something, this seems like you're trying to pick fly poop out of pepper.

Regards,
Ray L.

Your calculator is broken Ray either that or your millions are different from the UK ones, regardless however what you are saying is correct and that is why I wish to see pics of this machine as I have never seen one capable of such a degree of accuracy.
Hood

Edit!!!!!!
oops I need to go to here http://www.specsavers.co.uk/index.php?gclid=COzcjZ-W4ZYCFQ_UlAodW1ZCOg  I think, sorry ray never noticed you said 50

Go back and read my last post, I explain how I set the machine coords via oem code. I can zero my work coords with no issues or even type in those DROs and expected machine coords to behave the same and they don't. Apparently no one agrees that it should work that way guess I'll just have to live with it.

According to one of our customers the machine within the area of a few centimeters is repeatable to about 5microns (0.005mm). Me personally when I cut parts I shoot for around +/-0.05mm, my parts are also a little larger in scale. As far as the spec of the machine we don't quote any.
 
You can see the machine at http://www.minitech.com the Mininmill3 pro which is on the homepage.

Brian