I have entered all the motor tuning sections of Mach 3 as per instructions from the internet and information booklet provided. I can't get the axis to be correct with measurements. They are out a lot. Only moving about 40% of DRO movement. The calibration setting does not help. I can make the said changes and it is still very inaccurate. Changing the velocity and acceleration is also changing the distance the axis will travel. I have a Taig micromill 2000 and have set the motor tuning parts in inches to 8000 steps/25 Velocity/5 acceleration/5 step pulse/5 dir pulse. Increasing the steps from 8000 to 16000 is not doubling the distance travelled. I have tried several things and looked up as much as I can, but to no avail. If anyone can help me it would be greatly appreciated.

I have been using MACH 3 with a Taig mill for sometime now and am very pleased with the results I have gotten.  Repeatability and accuracy have been very good whether making small or large pieces that stretch the limits of the bed.   The same has been true when using the 4th axis to engrave rings and other cylindrical objects. 

If you want I can send you the settings I use and you can see if your results are better.

Bob@BobsShop

Try setting the velocity at 5 just to see if it helps.

Mike