On Fri, 30 Apr 2010 15:54:19 +0100, 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!

Since you have a Windows machine, you already have a decent calculator
as part of the O/S. Just fire up calc, and if it comes up as a
4-function, switch to "Scientific" from the View menu. The setting
should stick unless you have a Naz^H^H^H control freak IT guy limiting
your permissions.

Many enhanced keyboards even have a handy dedicated key to fire it up,
right over the number pad.

BTW, the Windows 7 calculator is fancier with more modes and is more
eye-candy-like than the old reliable XP/Win2k calculator, but they did
manage to break one useful ability of the older calculator. If you do
some calculations in floating point decimal and then want to convert
it to hex, you can't without re-entering the numbers because it clears
when you change from Scientific to Programmer modes. Best to copy the
old one over if this matters to you.

In this case, you could use sin/cos to calculate the y and x movements
required. sin(45°) = cos(45°) = sqrt(2) ~= 0.7071. So if the PCD was
3", you'd multiply the radius (half of that) * sin(45) to get the
y motion required (about 1.061") and for 45 degrees, the x motion is
the same. Then crank the x back double that (2.123") to drill the
left-hand hole, if I understood your description correctly.