my build from the start

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Originally Posted by Jonathan

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!

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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))

should be x/cos(whatever), as you're working out the hypotenuse from the adjacent.

fair do's
I've updated by guesswork...

Quote:

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Originally Posted by m_c

should be x/cos(whatever), as you're working out the hypotenuse from the adjacent.

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Yes it is, sorry ... was rushing and missed that :redface:

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

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

and here's how i sorted it :smile: there was play between the bearings so skimmed 0.76mm of the end cap no more play :smile: backlash now down to 0.003
http://www.youtube.com/watch?v=I8_JhbRmj7Y

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


Attachment 3552 Attachment 3551

Quote:

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Originally Posted by h4ppy-chris

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


Attachment 3552 Attachment 3551

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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?

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

Quote:

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Originally Posted by h4ppy-chris

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

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Here's a couple of photos of mine, pretty self explanatory...

cheers mate that's give me some think to think about.