The depth caliper is the only one with perfect accuracy. The digital caliper is not as reliable as I'd hoped, as the prongs can get stuck in a groove in the tread pattern. I will list my measuring methods and results.:
Gel Game 3
Bar Clamp method - 3.15 cm
Depth Caliper - 2.95 cm
Paper - 3 cm
Digital Outside Caliper - 3.25 cm
Last edited by newyorkstadium; 02-07-2014 at 12:04 PM.