Lead Screw/Motor Couplers

Hey gang. Need a little help here. I am in the process of reworking my LongMill table and also adjusting certain things. I removed the eccentric nuts and cleaned out the paint so I can adjust the rail wheels better. I am also trying to disconnect the motor to lead screw couplers. My problem is I can’t seem to loosen the set screws in the coupler. They are very very tight. Broke the tip off of my ball nosed allen wrench trying to loosen. I didn’t know I was so strong that I tightened them that much. I didn’t used any type of thread lock. Any ideas on how to loosen them appreciated.

Heyward: Get some penetrating oil into the set screw hole and let it soak through over night. If you can somehow support the coupler, putting the allen wrench into the screw head and tapping it with a hammer often works on boats with seized stainless bolts. Since you can’t really pound on the set screw without damaging things, a small, sharp tap may do it. Maybe you could put a block under the couple to take the shock. Another option will be to get an impact resistant allen bit, chuck it up in a impact driver and vibrate it out.
Ball nose bits are the worst since they are weak at the waist between the ball nose and the shaft of the wrench.

That’s all I’ve got.

1 Like

Thanks Grant. I’ll give that a shot. I know I tightened them pretty good to keep them from slipping but didn’t think I got them that tight. The allen wrench is small and bends before getting super tight. I thought about trying heat but not around all that plastic and bearings. I’ll post back if I am successful.

Good luck, Heyward. In your defence (not that you need one) there may be more going on here than your excess strength. I’m not in sight of my Mill right now, but if I recall correctly, the couplers are aluminum and the set screws are steel. I am far from a scientist, but I believe that there can be a galvanic reaction between those two materials that causes a “rust” of sorts to form on the joint. I know that, on boats, the combination of salt air/water - stainless steel - and aluminum is deadly.

Thanks Grant. I know what you mean about the corrosion. We used to live on the coast in Georgia and of course had a boat. Impossible to prevent it. Especially on the outdrive. I believe that may be part of the issue since my machine is in my unheated garage so it does get a bit extra humidity. I treated the set screws this morning and going to let them soak until this evening and see what happens.

1 Like

Grant, unfortunately the lubricant didn’t help much. The screw moved about a hairs width and then froze again. I ended up stripping the heads and having to drill them out which of course messed up the couplers. They aren’t listed on the store web site so am getting in touch with the Sienci team to see how to order them.

Already tried to heat up the coupler? On car parts this method works like charm, but often causes damage to plastic or gum. Here, maybe you can give it a gently try with a heat gun.

Thanks for the suggestion. Unfortunately too much plastic too close. I ended up drilling out the set screws. Of course that messed up the couplers. Ordering new ones.

That’s a bitch, Heyward. Is there enough material to drill and tap them for bigger set screws? Being an impatient type, I would not be pleased at having to wait for replacements. :slightly_smiling_face:

Watching Chris’ video, it looks like the V2 couplers are a different design, though. So maybe waiting would be a bonus.

I don’t think there’s enough material left. When I drilled them the screw heads popped off and left the screw shaft still in the coupler. I’m not sure if I have the tools to drill and tap the rest of it. Also I don’t know how much of a shoulder is left in the outer hole. It’s funny but I was looking on Amazon for replacements and found the exact same coupler but there was a statement in the part description that made me laugh. It said “Not Easy To Remove”. I emailed Sienci and Andy said the were out of V1 couplers and the V2’s are different and I would probably have to drill out some rubber. Not me. He said to get solid ones. I ordered from Amazon yesterday and should be here next Thursday. Thanks for trying to help though.

Heyward: I’m seeing all kinds on amazon. Can you pls post a link to the one that will ours? I’m too lazy to measure the bores on ours. I know that they are different on each end.

Grant, this is what Andy sent me for size: 6.35mm to 8mm couplers and solid ones. My old ones are 25mm in length and 20mm in diameter. I can find many with the correct hole sizes and 25mm in length. But the diameter varies. The ones I ordered are 14mm in diameter but solid so I’m hoping solid enough. I looked at the ones on Amazon like the V2 versions but they seem to have a rubber cushion of some sort. I don’t see how they would be any better as they will flex. I like the solid ones as they seem to have bigger set screws with 4 screws per coupler. I ended up ordering off of Ebay because the shipping times for Amazon were way out. Like late April, May and even June. I ordered from a US supplier last night and they are already shipped and due April 2. The were $8/pair (USD) so had to order quantity 2. Will have one extra if needed. Here is link - https://www.ebay.com/itm/2-pcs-Aluminum-Blue-Shaft-Coupling-Rigid-Coupler-Motor-Connector-CNC-DIY/353020805184?ssPageName=STRK%3AMEBIDX%3AIT&var=622229448895&_trksid=p2060353.m2749.l2649
Oh! And free shipping.

Good to know. I’m fine so far, but it’s always good to have a list of sources. I have metric drill bits and am thinking that if I can find some 20mm aluminum rod, I can make some. Boring it would be simple. Drilling and tapping for the set screws would be a bigger challenge.

I’m sure there’s 20mm rod out there. Just make sure it’s hard enough to take the stress. I have the drill press and bits but not the taps. And I have never done that before so not really willing to try yet. That’s pretty much why I just ordered. Good luck if you try it.

I put a steel machine screw into aluminum and it locked up halfway in. The threads were clean, never could get it out. Never again will I put a steel screw into aluminum without anti-seize.

1 Like