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  1. #11
    Quote Originally Posted by John S View Post
    The only type of drive that can handle miss-alignment in two axis is the Oldham coupling
    Looking at the specs Oldham couplings tolerate a surprisingly small amount of misalignment, not that that's a reason not to use them since you're doing something wrong if you can't get the shafts close enough...

    Timing belts / pulleys are clearly the best solution for driving ballscrews... numerous reasons, but that's not really relevant here.

    Hank, if you'd like me to make the part and can send me the drawing by tomorrow morning I should be able to fit it in. I've got plenty of aluminium bar, lots of sizes up to 3.5".
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  2. #12
    Quote Originally Posted by Jonathan View Post
    Looking at the specs Oldham couplings tolerate a surprisingly small amount of misalignment, not that that's a reason not to use them since you're doing something wrong if you can't get the shafts close enough...
    Get your head out of theory spec sheets and into real life.

    http://www.youtube.com/watch?v=utEKKox2WHA

    True you should get them bang on, not close enough, 10 thou out is as bad as 100 thou out.
    John S -

  3. #13
    Clearly the allowable misalignment is inversely proportional to the speed...as you said in the previous post misalignment absorbs power from the motor, in this case through friction. Since steppers are, relatively speaking, such low power motors this is obviously bad, even if the coupling does tolerate it in reality. I'm sure the manufacturers are conservative with the ratings. Hmm, I'm stating the obvious now, tend to make my own anyway.

    This is much more interesting:

    http://www.youtube.com/watch?v=G2DU1...ture=endscreen
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  4. #14
    Help, my "can you ID these couplings thread" has morphed into a fledgling technical debate" :-) (there must be something in the air around these parts?!)

    Thanks for all the input...I guess the answer is "no, you can't buy 'em"...so when it comes to it, I'll have to get a better one made than the one I made myself......I'll limp on for now as it does work.

    Thanks for the offers....I'll take one of you up on it when I get past my "make do" phase (which - using past history as a precedent - this phase will last far longer than it ought to)


    Next question....where do you go to get a heap of 1.6mm thick mild steel in small rectangles made? (something like 4mm x 7mm x 1.6mm) ...I've looked in the local rag, but there's no "Small steel rectangle makers" in there!

    Or if you were faced with having to make a few hundred....how would you approach it?
    Last edited by HankMcSpank; 15-04-2012 at 01:23 PM.

  5. #15
    Have them laser cut.
    John S -

  6. #16
    Quote Originally Posted by John S View Post
    Have them laser cut.
    Thanks - Is there a 'goto' laser cutter merchant that folks have used on here & can recommend?

  7. #17
    Quote Originally Posted by HankMcSpank View Post
    Thanks - Is there a 'goto' laser cutter merchant that folks have used on here & can recommend?
    I've used 'True-Cut'. They were cheap at the time (few years ago) and the service was excellent...

    http://www.truecut.co.uk/
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  8. #18
    ecat's Avatar
    Location unknown. Last Activity: 08-02-2014 Has been a member for 6-7 years. Has a total post count of 157. Received thanks 5 times, giving thanks to others 8 times.
    These guys, http://www.cncworkshop.co.uk/ , advertise on this very site (through AdSense at least)... for anyone who doesn't read the advertisements :wink-new:. They only do MDF in house, for metal they use http://www.essexlaser.co.uk/laser.html . The Essex bunch have 100 minimum order, boo, but I think that includes the cost of materials so for a large order they may be worth a try.

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