Thread: my build from the start

1. 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!
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??)

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

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

4. Originally Posted by m_c
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. 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. 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.

7. Originally Posted by h4ppy-chris
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.

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

9. Originally Posted by h4ppy-chris
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...

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

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