Cold Saw/Measure Flat Calc
The swivel plate's hole is 56mm from the front edge and 100mm from the side edge, approximately.
Using pythagorean theorem, distance between swivel hole's center and one of the front corners is 115mm, approximately.
For minimum cutting angle of 90 degrees (45 deg in both directions), the minimum measure flat length is the arc between 2 points of a circle.
Those 2 points are 90 degrees apart; 360 deg is full circle angle; hence 90 / 360 = 1/4 as fraction of circumference required.
Circle circumference is diameter x pi.
Minimum measure flat length = (115mm x 2 x 3.14) / 4 = 180mm, approximately