Pm-728vt conversion

[Toolmaker335xi]

Well I picked up the conversion kit last Monday and overall happy with the kit. I do have some minor complaints about it.

Everything bolted up and fit as it should. I wasn’t disappointed with the cast iron bearing blocks and motor mounts and they justified the 8 month wait for this kit.

I ended up getting some cheap Nema 23 570oz dual shaft steppers instead of trying to fit the 34’s I already had. I made some adapters for the shafts to work since they were 1/4” also I could still use the hand wheels. That’s when I noticed something was off.

The Y axis ballscrew is the same hand thread as the X axis! Therefore the Y axis moves in the opposite direction as it normally would. This was disappointing, I took the extra effort to still have hand cranks but can’t really use them.

The other thing that wasn’t so great was I have approximately .001” backlash in X and .003 in Y. Not sure if it’s on the ballnut or if it on the shaft coupler. I welcome any suggestions on remedying this. I can’t pickup any axial play on the shaft.

Other than those two things, I’m happy with the kit. I haven’t installed the Z axis yet. I wanted to have it somewhat of a manual mill with contouring capabilities for now.

I’ll post some pictures of the adapters I made when I get a chance. Also when I get my limit switches mounted. I printed up some brackets and need to test fit before I make them out of aluminum.

Also printed a little wrench to snug up the lock nuts.

 

[Toolmaker335xi]

Can anyone tell me how much torque should be on the lock nuts?

I only snugged them lightly till I had about .0002” axial play when going back an forth with the hand crank. But if I lightly tighten the table stop, only enough that there a slight resistance. I get about .0015” axial play on the end of the ballscrew.

I don’t want to over tighten and damage the bearings. Is the amount of axial play I have normal?

 

[Loftfan]

Can anyone tell me how much torque should be on the lock nuts?

I only snugged them lightly till I had about .0002” axial play when going back an forth with the hand crank. But if I lightly tighten the table stop, only enough that there a slight resistance. I get about .0015” axial play on the end of the ballscrew.

I don’t want to over tighten and damage the bearings. Is the amount of axial play I have normal?

How nice that your kit included a spanner wrench! Mine came with no such tool.

I'd like this answer as well. It makes sense to me that the bearing preload should be some percentage higher than the maximum ballscrew force so that the bearings are always loaded. I would have liked the engineers who put this kit together to have put the torque spec in the instructions.