Substitute ball for roller bearing?
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  1. #1
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    Default Substitute ball for roller bearing?

    I'm finding it hard / expensive to find replacement roller bearings for my lathe's QCGB, can find ball bearings the right size for a fifth the cost and wondering whether it'll make a difference that matters!

    The original spec' is Hoffmann RLS10LL, 1" ID, 2.250" OD, 0.625" width roller bearings with unflanged (demountable) outer races to allow ease of assembly - axial location is taken care of by pairs of opposed taper rollers. the RLS10LL allows some axial movement for thermal expansion also.
    Essential question, is replacing the rollers with available ball bearings going to affect the performance of the QCGB?

    LJ1 / RLS8 ball bearings are the right sizes (and relatively affordable), BUT aren't demountable (as far as I can tell), any recommendations for a demountable bearing with the right dimensions if it's impossible to reassemble the QCGB with built-up bearings? Less costly demountable rollers?

    Thanks in advance for any suggestions / yes do it / bad idea!

    Dave H. (the other one)

  2. #2
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    LRJ 1 are what you are looking for.

    LRJA as an alternative, which has a single flange on the outer race.

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    Quote Originally Posted by Hopefuldave View Post
    I'm finding it hard / expensive to find replacement roller bearings for my lathe's QCGB, can find ball bearings the right size for a fifth the cost and wondering whether it'll make a difference that matters!

    The original spec' is Hoffmann RLS10LL, 1" ID, 2.250" OD, 0.625" width roller bearings with unflanged (demountable) outer races to allow ease of assembly - axial location is taken care of by pairs of opposed taper rollers. the RLS10LL allows some axial movement for thermal expansion also.
    Essential question, is replacing the rollers with available ball bearings going to affect the performance of the QCGB?

    LJ1 / RLS8 ball bearings are the right sizes (and relatively affordable), BUT aren't demountable (as far as I can tell), any recommendations for a demountable bearing with the right dimensions if it's impossible to reassemble the QCGB with built-up bearings? Less costly demountable rollers?

    Thanks in advance for any suggestions / yes do it / bad idea!

    Dave H. (the other one)
    .
    Roller bearings can take more load or ball bearings are not heavy duty

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  6. #4
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    Thanks gents,

    I'm not too worried about load, they're outriggers supporting the imperial/metric selection gears on the end of 1" shafts carrying the cone of gears and the long gear the idler engages, the shafts are carried in big (1985/1986-1922) Timken taper rollers which carry the majority of the load - a bit overbuilt for a threads and feeds gearbox!

    It has been working pretty well but the bearings are rough and noisy, a previous owner had left out the seal on the (fully-enclosed oil-bath) cover and flooded the QCGB with coolant and there was a lot of corrosion on the races and rollers, damn gearbox is costing me almost what I paid for the lathe to put right(er)!

    My worry is that the box may be difficult-to-impossible to reassemble without the demountable bearings - only one way to find out, so I've ordered a trio of LJ1 ball bearings to play with! The taper rollers are the Unobtainium (for less than an arm and both legs) flanged versions (1922B outer race) for about 1000USD each (6 of 'em...) but I've found the flanged outer races at sensible prices, will do a bit of selective assembly with marker blue and base-model 1985 / 1986 bearings stripped of their outer races, here goes...

    Dave H. (the other one)

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    Might matter. Might not. I guess I'd first ask 'why did they use rollers' to begin with?

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    Just bear in mind....
    If you start changing press fits to slip fits
    things could wear out quick.
    There are engineering reasons for press fits.
    Just a cautionary note.

    -Doozer


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