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  1. #11
    Further, drill-rod as barrel, drilled and reamed and a secondary drill-rod as the endcap pressfit would likely cost about 2$/unit qty 3000.
    Advanced lathes run 250$/hr and should put out 240-300 pieces / hr.

    This would be a dead-easy job where lower unit costs are available.

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  3. #12
    To repeat myself because it's the quickest, simplest, cheapest and closest to requirements.
    Tube axle (fully inside the bracket)
    Holes in the bracket the same size as tube bore
    Hammer Drive screws will then fix the tube in place and prevent it rotating, drive screws don't require close tolerances for a good fit, definitely no requirement to ream, just drill.
    You think that's too expensive? You're not a Model Engineer are you? :D

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  5. #13
    I have got a wallpaper seam roller in the garage, I will see how that is done.

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  7. #14
    okay -

    so this seems like a viable solution. however, i would imagine that after pressing in the drive screws - they would probably 'slighting' bulge the inner tube - thus creating friction for the center barrel to rotate smoothly?

    is this correct?

    Click image for larger version. 

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  9. #15
    i should also add that these pieces are quite small - that center hole is 0.4 cm. i would need a ID tube of 0.4 cm with a reasonable wall thickness to prevent bulging?

    is something that small even available?

    Click image for larger version. 

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  11. #16
    It would help if you could give us an idea of what you are trying to achieve. I respect that you may not want to disclose the end use, but some indication of the forces involved may be useful. Also is the axle to be free to rotate in the yoke or must it be definitely fixed? Are you looking to scale up to produce many units, or are you making just one or two? What material is the roller? Will it be wet (aqueous), oily or dry in end use? Do you have a unit cost limit in mind?

    If you wanted a quick bodge you could pop rivet a length of tube into the yoke.

    BTW cm is not a preferred unit in engineering, metric users prefer mm. In the US they use inches a lot (but not excusively). Some of the Model Engineers in UK use imperial measure, while some of the absolute recidivists use Furlongs, Newtons per square fortnight, Firkins and Ducats per gross. Oh! and BA screws.

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  13. #17
    Quote Originally Posted by JEK5019 View Post
    okay -

    so this seems like a viable solution. however, i would imagine that after pressing in the drive screws - they would probably 'slighting' bulge the inner tube - thus creating friction for the center barrel to rotate smoothly?

    is this correct?

    Click image for larger version. 

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    No, it's not.
    Drive screws have a fast outer helix with a relatively high sharp profile, they are designed specifically for blind holes where the relative sizes can be chosen such that material distortion stays local to the hole walls, among other things they are commonly used to fix data plates to castings.
    You could make the holes in the bracket a tighter fit to give a lot of hold and the hole in the tube the right size to prevent rotation and give adequate retention without distortion of the outer.
    It's your job to experiment with drive screw size, tube hole size and wall thickness to get the materials behaviour you require for your application.
    You think that's too expensive? You're not a Model Engineer are you? :D

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  15. #18
    so i am in total agreement with you - and in fact, the attached image i posted yesterday was according to your idea.

    the only question i had - was would the drive screw slightly bulge the tube axle?

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  17. #19
    thanks magicniner. i guess it is a matter of experiment - much appreciated.

    i'm currently using mcmaster as a source for stock items (as it allows me to drop in the actual 3d product into fusion 360 - enabling the design) however, their tube selection seems rather marginal.

    do you have recommendations for manufacturers for smaller sized metal tubes?

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  19. #20
    thanks cropwell.

    so i looked up the wallpaper seam roller you had mentioned - and the design i am working will work just like that, in fact! but unlike many of the designs, i came across - where the roller bracket is on one side only - my design will be built like an axle.

    attached are several of these wallpaper seam rollers that more or less fit my goal and operation.

    in my design goal - i am wanting to avoid any welding/sanding finished. i would prefer fasteners - but with no drives. very clean!

    Click image for larger version. 

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    Click image for larger version. 

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