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 )