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  • threaded axle for removable roller?

    Discussion in 'The main mechanical design forum' started by yadnom1973, Jul 29, 2017.

    1. yadnom1973

      yadnom1973 Active Member

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      We have a small assembly that we have been working on and There is a roller that has to be changed every now and again for different ones. I was trying to think of a way to go about this and landed on the idea of threading the hub and threading the axel so the hub would be screwed onto the axle flush up against a shoulder in the shaft then a split threaded shaft collar would be screwed on and tightened up to fix it all in place.

      The axle is steel; the hub is aluminium and the collar steel. The hub, axle and collar are all M14 thread.

      It seems like a god idea to me but I can’t find any examples of this anywhere so I’m beginning to think that there must be something wrong with it. The only problem I can think of is that the whole lot would work undone but those shaft collars tighten down pretty solidly, that’s an M5 bolt in it.

      Any advise on why this is a bad idea would be appreciated and any alternative ideas welcome.

      P.S. I forgot to mention a pretty vital fact, I guess thought it was apparent from the drawing and description but maybe I'd better clarify that the rollers/gears are fixed to the shaft, the shaft sits in bearings.
       
      Last edited: Jul 30, 2017
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    3. yadnom1973

      yadnom1973 Active Member

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      Threaded hub question.JPG

      Here's the set up in SW, thread not represented but you can see where it would be.
       
    4. DEBANG ALUMINUM CASTING

      DEBANG ALUMINUM CASTING Member

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    5. PWASS

      PWASS Well-Known Member

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    6. yadnom1973

      yadnom1973 Active Member

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      One of the problems here and one of the reasons for the threaded shaft idea is how little space there is. The shaft is 14mm though I could push it slightly below if I had too and the hub is 25mm with Polyurethane bonded tread. So I couldn’t go above 19mm diameter bore. . So if I pushed to 13mm that’s 3mm clearance between the hub and the shaft to slot a keyless locking device into. I was going to say they don't make them that small but a quick check shows that a few companies do make micro ones for smaller shafts but whether 3mm clearance would work, I don’t know.

      I could have one that fits over the top if there was a boss on the roller but it makes problems for folk moulding the polyurethane.

      I think they are great little things but I do also have some concern about the end user having to take it on and off, I don't know how forgiving they are but the documentation is very specific about the torque required to fix one in place. They are also very expensive last time I checked but again that was the larger models maybe the smaller ones are more reasonable.

      Thanks for posting PWASS, it’s an idea, I’ll do a bit more research.

      Do you think the threaded hub and threaded locking collar is not a workable solution? Or were you just suggesting other options? I’ve still not had any luck finding any examples of things fixed to a shaft in this manner.
       
    7. s.weinberg

      s.weinberg Well-Known Member EngineeringClicks Expert

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      I can't see anything obviously wrong with the idea, other than that you'll probably get a bit of wiggle in the system, as it looks like you're just sliding the locking collar into place before tightening.
      How are you making the threads? If they're smaller than the shaft OD, then the manufacturing method is a bit more limited. If they're bigger, it will prevent the collar from entering the threaded portion, though you can just have the threads end a bit earlier.

      My main question is what you are aiming to achieve? Why not fix rotation with a standard method, like a key, spline, D-cut, set, screw, or whatever, and then have a retaining ring, collar, set screw, or some other standard way of preventing axial movement?
       

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