I’m in the process of installing the Masso conversion kit on my original Onefinity X35 Woodworker and have run into a potential issue with the stepper motor flexible (Plum-style) shaft couplers. Since the original stepper motors have 6mm shafts and the new Masso motors use 8mm shafts, I first had to order replacement couplers.
However, after receiving them—and as shown in the photo—I noticed the stock couplers use two types of screws:
A Socket Head Cap Screw to clamp the coupler around the shaft.
A small set screw (grub screw) that registers with and tightens against the flat on each shaft.
I’m not entirely sure of the technical term for these couplers—I’ve seen it referred to briefly as a “D-Flat” type coupler—but that name doesn’t seem to appear at any retailer. I’ve searched not only on Amazon but also on more specialized sites like McMaster-Carr and StepperOnline, and I haven’t been able to locate these dual-screw style couplers.
My concern is that without the additional grub screw securing the coupler to the shaft flat, the coupler may slip under heavy load. I’d really appreciate it if anyone could help identify where to buy these dual-screw couplers—or confirm with confidence whether the grub screw is actually necessary.
Does the z and other points have a 6mm shaft as well, so you sound need a 6mm to 8mm coupler?
As you probably thought, the grub screw would allow for an extra bit of security
Yes, all of the stock stepper motors have 6mm shafts.
The Z-axis slider uses an 8mm ball screw shaft end, so I purchased an 8mm-to-8mm coupler.
The X and Y axes both use 10mm ball screw shaft ends, so I bought four 8mm-to-10mm couplers.
That said, after just going out to the machine to double-check these dimensions, I noticed that the ball screw ends where the couplers attach do not have a flat side—it’s only the stepper motor shafts (both stock and new) that do. And considering I’ve been running this setup for the past four years without noticing any slippage, if nobody can find these double-screw couplers, I think I’ll go ahead and install the new parts this weekend and see how it goes.
I wasnt able to find them either in any size, and had success searching set screw and then clamp style but not set screw with clamp style. Makes me think they get it custom made, but the volume requirement for that is probably pretty high.
When you put them on, use a drop or 2 of blue loctite. If you were to experience a problem it would only be under high load or high speed resulting in it not being torqued enough… so i would say “don’t be shy”
