Lead screw couplers not securing the lead screw

My X-axis lead screw coupler does not properly secure the lead screw. I‘ve tightened the coupler screw, the lead screw still comes out of the coupler when using the machine.

The coupler design is not sufficient for securing the lead screws. The X-axis coupler is completely bottomed out and I can easily pull the lead screw out.
I’m stopped from any further work on my MK2.

Has anyone tried using CA glue to secure these couplers??

Do you have the 30x30 or the 48x30? I ask because the 48 has a larger lead screw and larger coupler. The 30 has the same size lead screws all around. So I was wondering if maybe you have the 30x30 but got the bigger coupler by mistake.

As far as the super glue I’m not sure if it would work and it would be hard to undo. I have heard of wrapping the rod with sandpaper to make it a bigger so the coupler will have more bite.

I have the 3030. I think that might be the problem. As I said earlier, I’ve bottomed out the coupler screw and it still is not secure.

If you have the wrong coupler I’m pretty sure it’s bigger externally and you could take it off and compare with the others. I hear good things about Sienci’s support so I would contact them if that’s the case.

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@dpalm888 I believe that @_Michael has identified the problem already, David, but I’ve moved your post to the Machine Help topic to help it gets the appropriate level of support.

Thank you!! Would like to get back to work on my MK2.

I used some duct tape on the end of the screw and that works. Problem solved for now

I had the same problem and tried a bunch of suggestions and nothing worked. I finally just mixed together a little 2 part epoxy and put it on the end of the threads, put it in to the coupler and tighten it down, then waited 24 hours. Been working perfectly ever since.

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I ground flats on my leadscrews for the grub screws to tighten onto.

Unfortunately that won’t wont work with a LongMill, at least not with the stock coupler because the couplers don’t have grub screws.

Kudos to you for building your own CNC though. It’s something that I have thought of doing. Either that or a 3D printer but I’m not sure I could pull it off.

How do you fasten the coupler to the lead screw and stepper shaft?

Screenshot 2023-10-30 175652

A picture says it all. It just squeezes the rod.

Mine is similar but also has a grub screw as well


Where did you get the metal coupler???
Inquiring minds want to know!!!

I bought them from my local supplier. I’m in Australia

See 2nd and 4th picture.

This one on Amazon looks pretty similar to the one Lappa has.

Order their new couplers. Bigger

Are there actual matching threads inside the coupler for the lead screw??

@dpalm888 No, they are not threaded.