The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

The New Hotness

  • Miniature Ball Bearing Sizes

    Having had to look up ball bearing sizes far too often, here’s the table…

    Bearing ID OD Thick
    603 3 9 5
    623 3 10 4
    633 3 13 5
    683 3 7 3
    693 3 8 4
    605 5 14 5
    625 5 16 5
    635 5 19 6
    606 6 17 6
    626 6 19 6
    608 8 22 7
    629 9 26 8

    The first digit is something like the bearing type; I think 6xx = miniature bearings.

    The second digit has something to do with the overall size, but is a code rather than an actual dimension.

    The last digit is, hal-lay-loo-ya, the actual bore diameter.

    [Update: Shows what I know; an excellent explanation of the numbers lives there. The short summary:

    • First digit: bearing type, 6 = single row deep groove
    • Second digit: series, 0 = extra light, 2 = light, 3 = medium duty, 8 & 9 = thinner
    • If three digits, third digit = ID in mm
    • If four digits, last two = ID/5, except 00-03 = 10/12/15/17

    Moral: always verify everything you read on the InterTubes!]

    Of course, a randomly chosen eBay listing will list the bearing size as:

    • ID x thickness x OD
    • OD x thickness x ID
    • ID x OD x thickness
    • and be wrong in at least one dimension

    Of most interest to Thing-O-Matic hackers: a 635 bearing ought to fit a NEMA 17 stepper shaft (pay attention if you’re buying surplus: not all are 5 mm) and slip into the same hole as a 626 bearing.

    Alas, there seems to be no 5 mm ID bearing equivalent to the 606 bearing in the MK5 extruder head, but a 0.5 mm = 20 mil shim around the outside would adapt a 625 to that hole. Might take some careful forming, though.

    Buy ’em in bulk and save…