TIght Bearing Issues

Hello everyone,

I am just starting my assembly of the longmill 30X30 and all my bearings are extremely tight.
I was able to use the locking washers on the Z axis to pull the bearings together but I am unable to make it work for the other areas.

Is there any fix, suggestions?

Thank you for all the help, it is appreciated.

  • Scott

@Scooter86 Welcome to the group, Scott.

I assume that you are talking about the flange bearings that fit into the steel plates for the X and Y gantries, yes?? It is likely that there is too much paint in the holes on those plates. The bearings should almost slip in. You may want to try a bit of sandpaper to remove the paint. If it looks like the difference between the OD of the bearings and the ID of the holes is more than paint could be causing, you should email the guys.

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Thank you im excited to get it all up and running.

My issue is actually the screw into the flange bearing, it does not slide in at all.

@Scooter86 Others here have posted about having the same issue, but I think that they all solved it with a bit of gentle persuasion. I did a search here on bearings and that’s all that I could find.

I appreciate the suggestion and will continue to find a work around. I definitely tried the gentle persuasion method but I was worried id damage the motors. These are extremely tight for some reason

@Scooter86 There is no spec that will tell you how hard you can push before you’ve pushed too hard, Scott. I would suggest that you disconnect one of the lead screws from its motor and use it to insert into all the bearings. That way, the motors are not in the picture at all.

Copy that, I appreciate your help.

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I’ve had the same issue. Measuring the bore of the inside race is 8 mm. My ACME screws were almost 8.15 mm. I tried everything I could think of. Sanding with sandpaper, emery, etc. Got the end of the rod in but it immediately became jammed. I tried some more persuasion and only got the bearing jammed onto the rod further.
Contacted Sienci and they sent me bearing and rods with the correct dimensions. Apparently it’s been a problem. Some can make it work and some can’t.
If you can’t make it work, give them a shout.
They are very helpful.
Hope that helps.

Thank you Dewey,
I was able to using some good ole WD-40… i coated the inside of the bearing and then the entire screw itself… it went in smooth but i did have to use the rubber mallet a little but nothing crazy.

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Yikes, I just ordered my Longmill a week ago, this is a bit concerning.

@rogdotcom I wouldn’t dwell on it, Roger. Only a very small number of owners have experienced an issue with this, and it was always dealt with one way or another. I realize that’s easy for me to say, as I did not have the problem. But, I believe that you can be reassured by the fact that Sienci will make it right.

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Some of my bearings were much too tight to fit on the lead screws. I ended up sanding the first 1 and a half inches of the lead screws to make the bearings go on with gentle taps. I used 220 regular sandpaper and sanded gently by hand. Worked fine.

Roger, it was really not that there is always a work around and it was actually a lot of fun to assemble the machine. Also, you have a good community here that is a wealth of knowledge. so far I am extremely happy with the machine and the company.


Just to reiterate, I had some problems but the crew at Sienci made sure I was looked after.
Great customer service.
Now I can’t wait to get making things!