Depth micrometers are a variant of traditional micrometers, but structured to detect precisely the depth of a groove or a step.
The structure of depth micrometer is the same of inside micrometer, but it has no frame and no anvil and has a body with grounded surfaces perpendicular to the axis of the rod (bridge).
The operation principle of this device is simple and immediate.
The measuring rod has to be retracted as possible; the surface of the bridge has to be set down on the outer surface of the hole. The operator ensures that the measuring rod is over the edge of the surface, above the hole to be tested; acting on the compass, the user drops the rod near the bottom; acting on the clutch, he puts into contact the prong on the bottom of the hole. Then, lock the rod with the brake and finally make the measurement.