Inside Micrometer, 3 Point, 25~30 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: Difference Between Inside Micrometer and Outside Micrometer

The inside micrometer is used to measure the diameter of the inner hole, and the outside micrometer is used to measure the diameter of the outer circle, and it can also measure the thickness.

The inside micrometer is used for precise measurement of inner dimensions. When measuring and using the inside micrometer, it must be connected with the micrometer head with the largest size rod and connected to the measuring contacts in sequence. When measuring the hole with the inside ruler, the measuring surface of the measuring contact should be supported on the surface to be measured, adjust the micrometer cylinder so that the measuring surface on one side of the micrometer cylinder swings in the radial section of the hole, find out the minimum size, then tighten the fixing screw to take it out and read it, or it can be read directly without tightening the screw.

The structure of the outer micrometer is composed of a fixed ruler frame, an anvil, a micrometer screw, a fixed sleeve, a micrometer cylinder, a force measuring device, and a locking structure. The reading of the measuring cylinder is basically the same as that of the inside micrometer. Therefore, the difference between the inside micrometer and the outside micrometer is the difference in the measurement method and measurement position.

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