Calculate the angle between two holes on the curved face of a cylinder. For this equation to work, the center of the holes must be co-planar perpendicular to the curved face. The value x is the shortest distance between two holes, that can be measured with a caliper using the external jaws.
*If chamfers are around the holes, this equation will fail on angles above 90°. You can measure up to 180° with no chamfers as long as the cylinder fits inside the caliper jaws.