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  1. #61
    Quote Originally Posted by Jonathan View Post
    Ahh just realised. My method can easily be extended to the general case for n bolts. You just need to know half the angle interior angle of the particular polygon. Then do cosine of that to get the factor...

    3 = Triangle, 60/2 = 30, so cos(30)
    4 = Square, 90/2 = 45, so cos(45)
    5 = pentagon, 108/2 = 54, so cos(54) = 0.5878 (!)
    6 = hexagon, 120/2 = 60, so cos(60) = 0.5

    The formula to find the interior angle is 180(n-2)/n.
    So that means, given n bolts with spacing x.

    r=cos(90(n-2)/n)
    PCD = 2*cos(90(n-2)/n)

    enjoy!
    my question is - none of these formulae use x - I'm sure they should somewhere?!?

    r= x/(cos(90(n-2)/n))
    PCD = x/(2*cos(90(n-2)/n))
    Last edited by mmcp42; 02-01-2011 at 04:03 PM. Reason: more correcter formula (mebbe??)
    there are 10 sorts of people in the world
    them as understand binary
    and thems as doesn't

  2. #62
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 4 Hours Ago Has been a member for 9-10 years. Has a total post count of 1,837. Received thanks 192 times, giving thanks to others 5 times.
    should be x/cos(whatever), as you're working out the hypotenuse from the adjacent.

  3. #63
    fair do's
    I've updated by guesswork...
    there are 10 sorts of people in the world
    them as understand binary
    and thems as doesn't

  4. #64
    Quote Originally Posted by m_c View Post
    should be x/cos(whatever), as you're working out the hypotenuse from the adjacent.
    Yes it is, sorry ... was rushing and missed that

  5. #65
    big time backlash on the z axis so time to investigate and here's what i found.



    and here's how i sorted it there was play between the bearings so skimmed 0.76mm of the end cap no more play backlash now down to 0.003

  6. #66
    well my ally turned up so made a start on the z motor plate
    all i could think of when making it was, if the mill was finished i would just be watching it being cut.


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  7. #67
    Quote Originally Posted by h4ppy-chris View Post
    well my ally turned up so made a start on the z motor plate
    all i could think of when making it was, if the mill was finished i would just be watching it being cut.


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    Similar to how I did it except I mounted the motor plate 90 degrees clockwise to yours, and lathed a bit of 3" aluminum bar to act as a spacer and give a bit more surface area for the motor plate to bolt on to. Doing it that way enables me to use the handle for manual drilling without removing the stepper - I think yours would collide?

  8. #68
    good point jonathan, i will wait till it's all working then make a new one.

  9. #69
    Quote Originally Posted by h4ppy-chris View Post
    good point jonathan, i will wait till it's all working then make a new one.
    Here's a couple of photos of mine, pretty self explanatory...
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  10. #70
    cheers mate that's give me some think to think about.

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