Try measuring across existing features - For example
Measure the distance from the outside edge of the flange to the outside edge of the screw,
then finding the radius of the screw and of the flange. Using the above I get
Screw to flange side - 23.86 mm
Flange radius 8.86 mm
Screw radius 1.90
23.86 - 8.86 - 1.90 gives a bolt hole radius of 13.1 mm
Jim Korman
Jim Korman