I tried searching to no avail. I even tried going through google with the (site:forums.reprap yadda yadda) command. Anyway...on to the question.


I am in the process of building my Prusa I3 Box frame. I have just about everything together to begin the build next weekend. However After trying the fit of the linear bearings (Yeah, I got them on Ebay) on the smooth rods I am very worried they are too tight. At first when I tried a few of them they would hardly move. I tried others and they slid right on and ran great. So after a whole bunch of reading I decided to clean my bearings out. I used Dawn and warm water in a spray bottle. Then let them soak in it for 45 minutes and another spray for each bearing. TONS of junk came out. Not the bearings, but bits of dirt/debris etc... So I them used sewing machine oil and re-lubed all of them. Now most 10 out of 12 run well enough. 2 are still very tight.

So my question, how tight is too tight? Should they all slide around on their own or should the stay in place if I hold the rod vertically until I toch them and move them?

I am sorry for the long post, but I am kinda wondering if I should order a whole second set of bearings.

Edited 1 time(s). Last edit at 10/03/2014 10:58PM by windcalmer.

The linear bearing moves along the length of the rod (obviously) and should feel smooth and almost friction free. They won't turn very well around the shaft, i.e. as if you were turning them with a spanner. That might be obvious, but I think it's worth mentioning.

They can sound scratchy, but the important thing is they move freely along the length, so if you've got bearings that are stiff, that's not good. It will put additional strain on your stepper motor making it run hotter, won't move as fast, and the whole thing will make a lot of unpleasant noise.

I'd be tempted to get new bearings now, it's a pain replacing the Y axis ones, the Z axis is a bit of a pain, and the X is quite easy. The Z axis is under the least stress as it moves slowly and infrequently, the Y axis ones (under the bed) are under a fair bit of load, but it is well spread across the bearings and generally feels easy to move. The X axis is under considerable load and you get a twisting effect from the carriage which stresses the bearings even more.

Thank you for the reply. So I guess I need to grab a second set of bearings and go from there.