ACME nut locks stripped

anyone else find that the m3 thread in the ACME nut lock is completely stripped and the set screw does not lock onto the thread just spins i will try to re-tape the thread to see if that fixes it will post back and see. also i found that the ACME thread for the Z axis was oversized from factory making it almost impossible to slide into the bearings and the nuts were extremely tight could barley get on by hand. This is a V2 longmill 30x30

Sounds like an odd manufacturing defect, were all the locking nuts like this?

Just the 1 nut the m3 was stripped i called and requested another to be shipped in the mean time i tapped it m4 and modifed a set screw. Got everything together just going to run some tests tomorrow.

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Great to hear Tristan, also thanks for the patience while we updated the instruction on the coupler assembly. Can’t wait to see your final machine setup! :ok_hand:

I had an issue with one of mine, although I may have bent the set screw or done something to it. I don’t think so. It appeared to be slightly bend because as the Y axis it was on spun it would rub and ring a bit at times. When I ordered a bunch of spare parts I ordered a few of the acme nuts and I’ve since replaced it. However, when I went to replace it I had a hell of a time getting the new unit to thread on. In the end I had to lock the motors powered on briefly and use a wrench, so there was something slightly amiss with the threaded on my lead screw. Whether it was the screw that affected the original nut or the nut was maybe slightly cross threaded on the screw or otherwise was out of spec I don’t know, but I figured I’d mention it in case you get any more reports similar to Tristan’s.


@jwoody18 Jeff. I read somewhere on the Sienci site, either the home site or this forum, that the set screws in the acme nuts enter at an angle. The nuts are to be threaded on that so that the set screw angles outwards. This makes it easier to tighten and also ensures that it does not hit the bearing on the end of the acme rod. I think that it’s likely that your set screws were not bent. They just looked that way since they were on an angle to the nut.

As i am from the manufacturing world i believe sienci labs needs to invest in some quality control for there outsourced parts. Quick checks that there customers will greatly appreciate. Like checking the thread sizes on lead screws. Checking ACME nuts for damage and the set screw threads. And if this is already being done in house. Maybe up the percent checked. It would be unfortunate for someone living further away to receive a machine with a bad part and then be stuck waiting for a replacement. Before they can fire up there lovely long mill. Just a suggestion. I did just tap mine with an m4 tap till my replacements came.

Grant, this is good to know. I went down the video assembly route rather than the (now very impressively documented and graphically annotated) written instructions. Chris was great in the five part videos but either I missed some of those points or perhaps the little details didn’t all make it in to the video. I should really go back and read the detailed instructions and make sure I haven’t missed anything, thanks for highlighting that!


@chrismakesstuff @jwoody18 Jeff: I looked last night and could not find it in the written instructions. I have a feeling that it was simply a comment in one of the discussions here.

Chris: Can you confirm if the set screws in the acme nuts do enter at an angle? I could just be making this up. :slightly_smiling_face:

The set screws should be going in straight. There is an issue you’ll run into then of the M5 bolt head hitting the leadscrew once the nut has worn out too much and this is one of the other advantages of using the smaller provided set screws (though, normally once it’s been worn out that far you should start to consider replacing the but altogether :slightly_smiling_face: )

@chrismakesstuff Tks, Chris

@jwoody18 Jeff: Sorry about the bad info. I’ll go away now. :grinning:

We’ve updated QA process for the next batch and package will include extras just in case anything slips through. The ACME locking nuts will also have a larger body as well to make sure that the M3 head cannot contact the face of the bearing even with some variance of where the location of the drilled and tapped hole is. (y)

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