How do I change millimeters into degrees?

Question

I have a Flange gasket with a pcd of $833 \ \text{mm}$ and I need to put a slotted hole at $12$ equal places that is $18 \ \text{mm}\times 28 \ \text{mm}$ long with rounded ends. How do I divide the $833 \ \text{mm}\times 360^{\circ}$?

Answer 1

Presumably a pcd is something circle diameter so you want $12$ holes equally spaced on an $833$ mm diameter circle. $MJ=MK=416.5$ mm $\angle JMK=30^\circ\ MNK$ is a right triangle with $\angle NMK=15^\circ$ so $NK=416.5\sin 15^\circ\approx 107.8$mm and the side of the dodecagon is twice this or about $315.6$ mm