Conduit diameter tolerance?

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This topic contains 7 replies, has 3 voices, and was last updated by Profile photo of C C 1 year, 4 months ago.

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  • #9130
    Profile photo of C
    C
    Participant

    My bearings finally arrived to I’m hoping to start building the frame this weekend. I decided to do a quick test fit of some of my parts earlier so I built up one of the rollers to try it for size on the conduit.
    Assembled to the point in the photo below, it’s a bit loose on the conduit. I recall reading about people finding the fit of parts to be very tight so I’m wondering if this is normal?
    Are the bolts through the motor mounts meant to tighten the fit once the nuts are on?

    I’m building the international version for 25mm conduit and my conduit outside diameter measures at about 24.65mm. Is that within tolerance for the build?

    Thanks.

    Roller

    #9139
    Profile photo of Ryan
    Ryan
    Keymaster

    That seems pretty far off from the usual for 25mm. You can tension it a bit with those long bolts. Sadly I think that is a bit too far off. Give it a try though. Loose to you might be okay, some people expect different tolerances.

    #9142
    Profile photo of C
    C
    Participant

    I think you’re right, it seems to be a bit too far off. With no nuts on the bolts there was a gap between the bearings and the conduit.
    I just gave it a try after tightening the bolts, it removed the slop so all three bearings were now touching the conduit but it wasn’t overly tight either. I’ve a feeling that when the coating wears off the conduit then the slop will return.

    I think the best thing to do is just get more conduit. It’s cheap so there’s no point in sacrificing the accuracy of the machine for the sake of tiny extra cost.
    I’ll just measure the conduit at the wholesaler when I’m getting it.

    Should all of the bearings be in contact with the conduit even without the bolts tensioned?

    #9239
    Profile photo of C
    C
    Participant

    Dropped into the wholesaler earlier to measure the diameter of some of the lengths of conduit. I was surprised by how much variation there actually is.
    Some lengths were up around 25.4mm at their widest point and others were down around 24.6. General variation on diameter was then .2-.3mm when rotating the tube in the caliper.

    Which diameter do you recommend picking up? 25mm exactly at the widest point?
    I’m assuming I should stay away from the ones around 25.4mm as that’s basically inch conduit and I read of other people having trouble using that.

    #9240
    Profile photo of Ryan
    Ryan
    Keymaster

    I’d say as close to 25 as you can get. once you get it put together you can always rotate your rails to get a good snug fit. Remember everyone is using basically the same exact product. It’s more forgiving than you’d expect but now you see why 25.4 doesn’t work, if you end up with some that is 25.7mm. That is why I try and step in whenever some says 25.4 works fine, maybe they just got a good batch or even a small batch.

    #9251
    Profile photo of Jason
    Jason
    Participant

    This makes me think… The 2 bearing holes on top (top when it is mounted on a rail) could they be elongated a bit.. then nut trap added to the inside to make them adjustable in situations like this? This would allow the 25mm version to work with 25mm rails and 25.4mm rails with out issue.

    #9253
    Profile photo of Ryan
    Ryan
    Keymaster

    Until you get to the center assembly then it becomes almost impossible to align it “normal to” the work surface.

    #9639
    Profile photo of C
    C
    Participant

    Just in case it helps anyone that comes along and reads this thread later…..
    I got a few more lengths of conduit and they measure between around 25.05mm and 24.7 mm as you rotate them and they’re a much better fit.
    No more slop in the roller assemblies even when they’re not tensioned and they’re a tighter but still smooth fit everywhere else. Would still like slightly more tension on the roller F sections but maybe that’s just me.
    For anyone trying to use inch (25.4mm) conduit, if the variance in diameter is as much as I’m finding in the metric conduit then you should hopefully be able to find a few lengths that are undersized and use those.

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