On Fri, 30 Apr 2010 14:26:44 -0700 (PDT), rangerssuck
wrote:

On Apr 30, 10:54*am, Chris Wilson wrote:
My maths is appalling, I am sorry to say. Yesterday I wanted to work out
the X and Y axis movement on a milling machine to drill two holes opposite
one another skewed 45 degrees from the vertical at a known PCD . I had the
machine zeroed on the centre of the hole around which these drillings were
needed. Took me ages as I have forgotten most of my Trig and I couldn't
find a suitable calculator Is there any easy to use engineering software
for this sort of thing? It's at times like this a CNC machine seems
wonderful Ta!

You want a bolt circle calculator. Here's a simple online one (nothing
to load into your computer):
http://www.selectsmart.com/darex/bolt_cir.cgi

Here's its solution to your problem:
2 holes in pattern
Bolt Circle Diameter: 3
Centered at: (0,0)
Starting angle: 45° (45° 0' 0" )
Ending angle: 45° (45° 0' 0" )

( 1.0607 , 1.0607 )
( 1.0607 , 1.0607 )

Hmm.. that's two holes in the same location.

You need to start from here, for some reason they didn't put a link
back to the form page that I can see.
http://www.selectsmart.com/darex/bolt_cir.html

I did this (assuming the holes are +/- 45 degrees relative
to 12 o'clock). The program take the x-axis (3 o'clock) as 0 degrees
and CCW angles as positive from what I can see.

2 holes in pattern
Bolt Circle Diameter: 3
Centered at: (0,0)
Starting angle: 45° (45° 0' 0" )
Ending angle: 135° (135° 0' 0" )


( 1.0607 , 1.0607 )
( -1.0607 , 1.0607 )