Ball bearing variability

[zephyr1934]

I'm starting to explore using MR85 for technic axles and I am wondering about the size consistency across manufacturers for these tiny ball bearings. So far I have only bought one set. The ones I got seem to be about 0.1 mm smaller than the specified 8mm x 2.5mm. Which I can totally live with. But I am wondering if that is typical of all manufacturers. I can easily work with "consistently 0.1 mm too small," but it would be an ugly surprise if MR85 from another supplier (or a different lot from the same supplier) might wind up being larger than specified, e.g., 8.1mm in outer diameter.

 

I'm curious what others here have found about ball bearing size consistency, I know many folks are using MR52 for metal train axles and I am particularly interested in your experience.

 

[Toastie]

Germany calling

If you order them from companies like this one: https://www.kugellager-express.de/miniature-deep-groove-ball-bearing-mr52-zz-2x5x2-5-mm then you get the max. tolerances as well. I would rely on these data - and simply ask for replacement, if they go out of specs.

Best,
Thorsten 

[dr_spock]

The Chinese ones I ordered from Ebay all measured 7.93mm. 

[zephyr1934]

Thank you both for sharing your experiences.

I bought 10 ball bearings so far. Not completely sure what I want to do with the the technic axle versions, but they strike me as perfect for non-lego gauge builds (O and G), and of course steam engines. So far I have only modified one of my Maersk mods. Now it actually rolls after you push it (the original that still has the technic axles stops dead as soon as you stop pushing). Definitely not as good as the ball bearing wheel sets with the metal axle using the MR52 bearings. Might not even be as good as the discontinued lego wheel set with the metal axle, but it is probably in the same neighborhood. That is still helpful though for the times when you need a different wheel. The performance difference could be bad bearings, but more likely slop in my build. For example, the inner radius on the MR85 is 5 mm but the technic axles are roughly 4.8 mm so already they have flexibility within the bearings. My mounts are also a little loose. Damn that entropy!