Inside Micrometer, 3 Point, 16~20 mm Range

Q1: What is an inside micrometer?
A1: An inside micrometer is a device designed to precisely measure things such as the inner diameter of holes. They look like fountain pens with a rotating thimble in the middle. Every time the thimble is turned, the micrometer expands. The thimble expands until the end of each tool touches the inside of the pipe, then a numbering system is used to find the measurement on the thimble.

Q2: How does an inside micrometer work?
A2: The picture below shows a 3-point inside micrometer with a measuring range of 11~14mm. When the force measuring device 6 is rotated clockwise, it will drive the micrometer screw 3 to rotate and make it move along the helical direction of the threaded sleeve 4, so the square conical thread at the end of the micrometer screw will push the three measuring jaws 1 For radial movement. The elastic force of the torsion spring 2 makes the measuring claw fit tightly on the square conical thread, and expands and contracts with the advance and retreat of the micrometer screw. The radial pitch of the square conical thread of the 3-point internal diameter micrometer is 0.25mm. When the force-measuring device rotates clockwise for one revolution, the measuring jaw 1 will move outward (radially) by 0.25 mm, and the diameter of the circle formed by the three measuring jaws will increase by 0.5 mm. When the microtube rotates once, the measurement diameter increases by 0.5mm and 100 equal divisions are engraved on the circumference of the microtube, so its reading value is 0.5mm÷100=0.005mm. This is how an inside micrometer works.

Tips: Errors of the Inside Micrometer

The direct measurement error of the inside micrometer includes the force deformation error, temperature error and indication error of general measurement, reading aiming error, contact error and zero alignment error of the length measuring machine. The main factors affecting the measurement error of the inside micrometers are force deformation error and temperature error.

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