Micrometers Inside
Micrometers Inside
A caliper reaches inside a bore just far enough to be wrong about it. Inside micrometers measure that diameter properly, in two styles: small-range jaw-style micrometers for holes under about 2.2", available mechanical or IP54 electronic, and extension-rod micrometers with interchangeable rods for bores up to 12" or larger.
Fowler 0.2-1.2" Electronic IP54 Inside Micrometer
$277.00
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How to choose
Small vs. large bores
Jaw style vs. extension-rod style
Jaw-style inside micrometers work like a small caliper turned inward, reading directly for bores up to about 2.2". Extension-rod micrometers instead use a single micrometer head with swappable rods of different lengths, covering a much wider range, 2" to 12" or beyond, from one tool instead of a shelf of dedicated gages.
Reading method
Mechanical vs. electronic IP54
The small-range jaw-style inside micrometers come in a standard mechanical version and an IP54 electronic version with an LCD display. The electronic version costs more but reads faster and holds up better against light splash near a machine.
Sets
Why buy a set instead of a single tool
An inside micrometer set bundles the micrometer head with several extension rods of different lengths, covering a bore-diameter range that a single fixed-length tool can't. It's the more economical route if the shop measures bores across a range of sizes rather than one fixed diameter.
Common questions
Fowler's extension-rod inside micrometers extend from 2" up to 12" or more using interchangeable rods. For bores larger than that, a different tool such as a bore gage is usually a better fit.
Jaw-style inside micrometers work well in blind holes since they read directly at the bottom of the reach. Extension-rod styles need enough depth to seat both contact points, so check the rod length against the hole depth first.
Not inherently. Both are built to the same accuracy grade. The electronic version adds an LCD display and IP54 protection for faster reading and better resistance to shop-floor conditions, not a different accuracy tier.