What is a Bore Gage?
A bore gage is an instrument designed to measure the ID of a round hole. Bore gages come in many styles with different levels of accuracy. A simple round pin would check for a hole being good or bad (functional) a rocking style bore gage usually has more range but must use a mastering system. Self -centering bore gages are variable and best suited for mass production where you need to take the human influence out (skill out of the measurement). Tolerance dictates the best method for the measurement.