# Bolt Circle Calculator



## rake60 (Aug 5, 2007)

I used the sub-division method of laying out a bolt circle for a long 
time.  It works well using the formula :

B  = D x sin( 360 / 2 x N)
where 
B = distance between bolt holes
D = diameter of bolt circle
N = number of holes in circle

But the Bolt Circle Solver at *Darex* makes it a whole lot easier.
It gives the X and Y coordinates without all the calculator work.

If there's an easier way why not use it?


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## MetalZilla (Aug 22, 2013)

Try using the bolt circle calculator in the Web Machinist software program: http://www.webmachinist.net/boltcirclecalculator.html
Works very well.


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## TNvolute (Jan 19, 2014)

Little machine Shop has a Reference page that has several calculators Including bolt circle, determining a bolt circle diameter from chordal measurements (very handy for odd-numbered bolt circles) and a change gear calculator for several of the mini lathes as well as one you can set up for ANY lathe:

http://littlemachineshop.com/Reference/reference.php


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