[chevytrucking]

Every design known to man, every shaft size combo at your fingertips. Cheap too.
stepper couplers | eBay

How right you are. Just found the couplings I need on ebay for $2.50 each. From China, but so is the mill, so hey it works.

[Fastest1]

Sometimes the stuff arrives almost instantly other times weeks. It's weird. I might be a little suspicious of 2.50 coupler ;-)


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[chevytrucking]

I was little shocked at the price, don't know how they do it unless its just some kind of overstock or something. Here's they are, got 2 for 5$.
Attachment 319490

[Fastest1]

It is amazing just how inexpensive some things are, even including shipping.

[vegipete]

I would stick with the solid motor coupling to start. You appear to only have thrust bearings on the ball screw, and no radial bearing. At 13:13 of video 6, you can see the end of the ball screw floating around as you touch it. The solid coupling will allow the motor bearings to hold the radial alignment of the screw. A solid coupling is bad if different radial bearings end up fighting each other, which is not the case here. Now whether the motor bearings can survive the somewhat higher loads is another matter but my first guess is it should be OK.

[phomann]

Solid couplers are never a good thing for motors. If the screw and motor are not perfectly aligned eventually the stepper motor shaft will fatigue.

Also, flexible couplers help absorb the effects of mid-band resonance. Without them you increase the chance of stalling the axis in the 2-6rps motor speed range.

Cheers,

Peter