When the small anvil and micrometer screw are brought together, the zero point of the movable scale does not coincide with the zero point of the fixed scale, and zero error will occur, which should be corrected, that is, the value of zero error should be removed from the final length measurement reading.

The structural feature of a pointed external diameter micrometer is a pointed head with two measuring surfaces of 45 ° vertebral body shape. It is suitable for measuring the groove diameter of small grooves, such as drill bits, vertical milling cutters, even groove taps, and the diameter of the tooth root circle of clock gears.