When test fitting the motors none of them will sit flush. They are off about 0.5mm to 1mm resulting in the motor being able to wobble ever so slightly. I’ve verified the coupler is inserted completely but when I try installing it on one of the ball screws there is slight gap such that the motors a…

Beveled the edge a bit more and after putting the coupler back together and test mounting the motor the motor is now fully flush on both the X and Y axis. :partying_face:

@DavidB If you install a motor without the coupler, how much of a gap is there between the shaft and the ball screw? If that gap is inferior to the plastic “spacer” in the coupler, then the motor will never sit flush without some sort of mod. I wonder if the ball screw can move laterally at all.

The motors sit flush without the coupler. I will have to measure the distance between the motor shaft end and ball screw end. Just strange that they don’t fit on the X or Y locations by same amount. The center section of motor does have raised section that does appear to fit into the large hole …

A question for AltMill owners. Is the opposite end of the ball screw shaft adjustable at all? Wondering if it’s possible that the whole shaft is somehow too far towards the motor side. It’s hard for me to tell from looking at OnShape. @DavidB I’m assuming that both sides of the coupler are loose wh…

Yes, I don’t tighten the screws on the coupler so both the motor shaft and the ball screw shaft side can move freely.

@DavidB I measured the spare coupler I had received with my Altmill. The thickness of the red plastic at the centre is 0.06" or 1.5mm. And the shafts should be able to go in by 0.57" (14.5mm) on both ends of the coupler

I’ll ask the obvious question but as I recall the couplers have an orientation and you did get that correct?

Yes, one side is I believe 8mm for motor shaft and other side 10mm for ball screw shaft if that is what you are referring to.

I do feel a little roughness on the face of the end of the ball screw shaft around the outside edge. Not sure if it is enough to keep the motor on the Y axis from sitting flush. I don’t see anything I can do especially on the Y axis since that is all one piece unless the coupler is messed up or so…

Sienci Community Forum

AltMill Motors not flush

Community Support 🛠️ Assembly

DavidB April 10, 2026, 3:32pm 10

Left side Y axis wobble:

Machine Y axis noises