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  1. Just out of curiosity, is there a rule-of-thumb for whether and when to use 5mm or 10mm pitch ballscrew when constructing an XYZ table (for routing mainly hardwoods)?

  2. #22
    Quote Originally Posted by Karl View Post
    Just out of curiosity, is there a rule-of-thumb for whether and when to use 5mm or 10mm pitch ballscrew when constructing an XYZ table (for routing mainly hardwoods)?
    It depends on numerous factors. 10mm pitch gets you much better speed and acceleration, but unless you use pulleys (which you really should...) you clearly have half the resolution of a 5mm pitch screw. If the axis is quite long you'll certainly want a 10mm pitch screw, since because the screw pitch is greater the rpm for a given feedrate is less so the screw will not whip until twice the feedrate it would with 5mm pitch. For a short axis, like Z, whipping isn't a problem so 5mm is fine. In most cases on a 'reasonable size' router 10mm pitch with pulleys is the way to go for X and Y and choose the pulley ratio depending on what your're cutting (to favour resolution for speed).

    However clearly there will always be exceptions and each case is different, so you need to read up on it, decide and calculate for yourself.

  3. #23
    Quote Originally Posted by Jonathan View Post
    7 days from ordering - not bad at all.
    Not if the bastards are wrong.!!!!!!!!!!!

  4. #24
    Jonathan the screws are correct and I owe a big apology to Chai. . . . Just spotted it's twin start thread.
    In my defence it's the first time he's sent me twin startscrew. . . . Better send him an email quick. .:whistling:

  5. #25
    Hope the ball nuts are double start as well:heehee:

    Peter

  6. #26
    Has Chai given you any load ratings or datasheet for these twin start screws? Would be interesting to see how they compare to the single start. Do the ball-nuts have two or four rows of balls and are they the same dimensions as the single start nuts?

  7. #27
    Quote Originally Posted by Jonathan View Post
    Has Chai given you any load ratings or datasheet for these twin start screws? Would be interesting to see how they compare to the single start. Do the ball-nuts have two or four rows of balls and are they the same dimensions as the single start nuts?
    Spot the difference.!!! . . . . Can You see know how I didn't spot It was 10mm pitch straight away.!! . . .The nut length gave it away.
    3 circuits (rows) 6 plugs. 3 circuits is a typical for 16mm dia, 4X usually on 20mm and above.!
    As you can see quite a bit longer body and obviously ever so slightly more resistance due to extra set of balls.


    No didn't get any Datasheet, I didn't even know he was sending me twin start so didn't ask. I will email him to see if he as any specs.

    Will be a couple of weeks before I have them on the machines and working so will let you know how they perform.?????
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  8. Quote Originally Posted by Jonathan View Post
    ... but unless you use pulleys (which you really should...) ...
    So what's the rationale for using pulleys to drive a ballscrew rather than connecting the stepper motor directly inline via a flexible coupling?

  9. #29
    Quote Originally Posted by Karl View Post
    So what's the rationale for using pulleys to drive a ballscrew rather than connecting the stepper motor directly inline via a flexible coupling?
    Couple reasons really.
    Easy to gear for extra speed or resolution/torque. It also helps reduce resonance that affects the motors.

  10. Quote Originally Posted by JAZZCNC View Post
    Couple reasons really.
    Easy to gear for extra speed or resolution/torque. It also helps reduce resonance that affects the motors.
    Many thanks - I hadn't considered the potential flexibility offered by interchangeable gearing.

    That raises the question: What brand/source of pulleys/belts are currently in fashion/recommended?

    {Presumably, belt manufacturers/suppliers provide tensioning guidance?}


    Thanks

    Karl

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