Amateur Machinists' Tools, Techniques and Materials

Archive for February, 2014

Taking pleasure in measure

Posted by hammerscale on February 13, 2014

Some measuring credos and observations on machining tolerances.

1: Measure with a micrometer, not a caliper.

2: The machining feed and speed should be the same. (in other words, dont take a measurement off a roughing cut.)

3: Make sure the micrometer is zeroed correctly. Use a known standard, or for a 0 to 1 inch micrometer, bring the anvil to a close.

4: Use the same feel and pressure when taking a measurement. It’s your fingers, get a consistent feel for how the mic closes.

5: Make sure both work piece and micrometer anvils are clean. Use your finger tips to feel for grit, contrary to pop opinion (a.k.a. old man foolishness) you do not need to clean the micro with a folded hundred dollar bill or any other nonsense, your finger tips are fine. The human finger can detect inconsistencies smaller than 1/10,000 of an inch.

6: Take multiple readings. With round work travel slowly across the diameter of the work piece. Gently wiggle the micrometer as you take a reading to fight any tendency of the anvil faces to skew instead of lay flat


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