The B22 cap is held by two pins that travel down a slot and then sideways into a locking detent. Unlike a screw cap, the insertion path is not symmetric, so the angular position of the pins is a functional dimension rather than a cosmetic one. Get the angle wrong and the lamp will enter but not lock, or will lock only when forced.
Pin diameter is checked with a plate gauge at both material conditions, as with any pin cap. Pin height above the cap face is checked separately, because a pin that is too high holds the cap off the holder and a pin that is too low fails to reach the detent. Both are simple go/no-go features but they need two different gauge faces.
The gauge that matters most is the functional one: a reference holder in which the cap must insert with light pressure, rotate through the specified angle, and lock without excessive force. This single check catches angle errors, pin height errors and shell diameter errors together, and it is the closest thing to the experience of the customer that a lab can reproduce.
A reference holder whose springs have softened will pass caps that a new holder rejects. Treat the reference holder as a measuring instrument: record its spring force at each calibration and replace the springs when the force falls outside the specified band. A holder that has been in daily use for years is usually the least trustworthy item in the room.
