D Murphy wrote in
:

wrote in news:1128260520.193820.206700
@g14g2000cwa.googlegroups.com:

I need some guidance on figuring out what the bolt hole co-ordinates
are to build a drive flange. The hub I need to bolt to has three
holes, evenly spaced with a center to center dimension of 3.607. How
do I calculate what the bolt hole x-y co-ordinates are to drill this
when held in the mill vice? thanks in advance, ron


Trigonometry.

Start by drawing a triangle with the center of your three holes as the
corners. Next draw two lines on each side of the triangle in such a
way that the triangle becomes a square. One of those lines is the
amount you need to move the table cross ways (X), the other is how far
you move toward an away from yourself (Y).

To solve for the sides of the right triangle you've just drawn:

Known - The hypoteneuse is 3.607" (side c)

Angle A = 30 degrees (the original triange has 180 degrees divided by
three equals 60 degrees in each corner. Since you made the new
triangle a right angle to the bottom of the original triangle you take
90 degrees minus 60 degrees and you have 30)

So now you know A and c. to solve for a and b:

a=c X sin A

b=c X cos A

a=1.8035

b=3.1238

If I did the math right.



I should add that you need to find the center of you work piece, then
move the table toward you 1.5619 for the first hole. Then move the table
1.8035 to the right and 3.1238 away from you for the second. For the
third move the table to the left 3.607"

But I would wait until someone else comes along and checks the math. I
haven't had enough coffee yet.

--

Dan