NOCTI Maintenance Practice Test

Which part of a micrometer provides 0.001 inch increments for measurement?

Thimble Sleeve Dial Ratchet

Correct Answer:

Thimble

Explanation:

The precise 0.001 inch increments come from the rotating thimble. The sleeve provides the coarse baseline in larger steps (the fixed scale on the body), while the thimble’s fine graduations give the thousandths of an inch as you rotate it. Each division on the thimble corresponds to 0.001 inch, so reading the thimble against the sleeve lets you determine measurements to thousandths. The ratchet knob isn’t a measuring scale; it just ensures consistent pressure to avoid over-tightening. If a dial is present, it’s usually another way to read the same thimble movement, but the actual 0.001 inch increments come from the thimble.

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