Micrometer Accessories

A 0-1 inch micrometer can be zeroed by closing the spindle directly onto the anvil since zero falls within its travel. Micrometers with a range starting above zero (1-2 inch, 2-3 inch, etc.) can't close that far, so a setting standard of the correct length is needed to verify the reading at a known point within that micrometer's range.

Frequency depends on usage intensity and the criticality of the measurements being made — instruments in daily precision use in a formal QC program are often checked before each use or shift, while lower-use instruments might follow a monthly or quarterly schedule; check your quality system's documented calibration interval requirement rather than relying on a single universal rule.

Carbide is significantly harder and more wear-resistant than the hardened steel typically used on standard micrometer faces, so carbide-tipped anvils and spindle tips hold their calibrated dimension much longer when repeatedly measuring abrasive materials or hardened parts — extending the interval between needed re-calibration or replacement.

A ratchet stop is a mechanism at the end of the micrometer's thimble that slips (ratchets) once a consistent, calibrated measuring force is reached, preventing the operator from over-tightening and compressing the part being measured. It significantly improves measurement repeatability, particularly across different operators who might otherwise apply inconsistent force with a plain friction thimble.

Gauge block grade should be at least one tolerance grade tighter than the micrometer's own stated accuracy — using a block with tolerance similar to or looser than the instrument being checked doesn't give a meaningful verification. Grade 0 or AS1 blocks are common choices for checking standard shop micrometers; higher-precision instruments need correspondingly higher-grade blocks.