Leon, In case your NC mill does not have bolt circle
program instructions here is a conversion program
from bolt circle to x y coordinates.

Paul Lamar
 
The AirCraft Rotary Engine NewsLetter.              Powered by Linux.

http://home.earthlink.net/~rotaryeng/            http://www.linux.org

CLS
radius = 5.875 / 2
OPEN "psruhole.dat" FOR OUTPUT AS #1

PRINT #1, "angle            x             y"

FOR angle1 = 15 TO 345 STEP 30

radian1 = angle1 / 57.295
PRINT #1, angle1,
PRINT #1, USING "###.###"; radius * SIN(radian1);
PRINT #1, USING "#######.###"; radius * COS(radian1)
NEXT

SHELL "more < psruhole.dat"

angle            x             y
 15             0.760      2.837
 45             2.077      2.077
 75             2.837      0.760
 105            2.837     -0.760
 135            2.077     -2.077
 165            0.760     -2.837
 195           -0.760     -2.837
 225           -2.077     -2.077
 255           -2.837     -0.760
 285           -2.837      0.760
 315           -2.077      2.077
 345           -0.760      2.837