Thanks so much for you reply. This is very helpful. I have decided to move ahead with the PM-833TV and will order it as soon as my new garage is completed.
I am still perplexed with the choice of steppers/ball screws required for the PM-833TV. The PM-833 is lighter than the PM-940. That guys at Arizona CNC who have built more conversion kits than anyone use a 1700 ounce stepper for the Z-Axis for the PM-940 and claim it has tons of torque for the job. They use either a 25mm or 32mm balls screw for the Z-axis. By contrast the ball screws from Bruce Nelson at Heavy Metals for the PM-833TV are 20mm and they suggest using a 2800 oz. stepper for the Z-axis. I don’t understand the use of a significantly larger stepper and a lighter duty ball screw.
Dr. D said he chose the 2800 oz stepper for added detent torque needed to hold the head stationary when the mill is depowered. However if the 1700 oz. stepper has enough detent torque to hold the PM-940, then I would think it would have no problem with the PM-833. Any thoughts on this?
I also just read a post on this forum from Sean about adding a gas strut to off-load the Z-axis. He noted
“The main reason I wanted to add the gas struts was to take the load off the double ball nut. The Z axis was not sounding smooth while in motion as compared to the X and Y. I was concerned running with that load on the double ball nut was going to lead to premature wear or failure of that mechanism.”
Todd, did you have to add a gas strut to the Z-axis? Did you use a 20mm ball net for the Z-Axis?
Thanks again… Richard