1. The inside micrometer consists of a casing with a large range and a measuring rod with a small range. When measuring the inside micrometer, first put the outer sleeve into the hole, and then measure the diameter of the hole by rotating the measuring rod. Three-claw micrometer is a measuring tool with three movable measuring claws, which is used to measure the inner diameter of the workpiece.

2. The internal micrometer is often used to measure the internal diameter of workpieces such as round holes and sleeve holes, and is suitable for a larger internal diameter range. Three-claw internal micrometer is used to clamp the inner wall of the workpiece with three claws and measure the diameter of the hole through the movement of the claws. It is suitable for measuring small holes, thin-walled workpieces and irregular holes. Because the claws of the three-claw internal micrometer can adapt to irregular holes, it is more flexible and accurate in some cases.