Each micrometer thimble has a constant-force mechanism, so that once the spindle contacts the surface of the measured object, it will stop tightening. This ensures repeatable measurements and prevents over-tightening.

Ratchet-stop thimbles have a speeder knob to reduce the time it takes to open and close the micrometer. When the spindle stops tightening, the thimble stops turning, but the speeder knob will continue turning with a clicking sound.