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Measurement tools and calibration · Lesson 3 of 4

Measurement tools and calibration: methods and worked application

The daily tool check; zero first; micrometer, caliper and protractor readings worked step by step; metric readings; rounding to 1/16 in; square and level checks; and the field measurement checklist.

You will be able to: Run a documented tool check, read a micrometer, vernier caliper and vernier protractor and record the result with its unit, convert and round the way AFS does, check a square and a level, and measure in the field against AFS's checklist.

13 min · 12 slides · 9 questions

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Slide 1 of 12

The daily tool check

This is a teaching sequence built from the makers' guidance, not an AFS procedure.

Clean the tool and the work, check the zero, then check against a reference.

If the tool is within its limit, use it and record the check.

If not, re-zero and re-check; if it is still out, tag it out and report it.

The daily tool check as a flowA flow from top to bottom: clean the tool and the work, check the zero, check against a reference, then a decision whether the tool is within its limit. Yes leads to use it and record the check. No leads to re-zero then re-check, then a second decision: if the tool is now within its limit, use it and record the check; if it is still out, tag it out and report it, send it for calibration where a certificate gives the value and uncertainty, then back in service with a record kept. A note says re-zeroing is adjustment, not calibration.The daily tool checkClean the tool and workCheck the zeroCheck against a referenceWithin thetool limit?YesUse it.Record thecheckNoRe-zero, then re-checkWithin thelimit now?YesNoStill out? Tag it outand report itSend for calibration:certificate gives valueand uncertaintyBack in service,record keptRe-zeroing isadjustment,not calibration.A teaching sequence, not an AFS procedure.

A flow: clean the tool and work, check the zero, check against a reference, then a decision whether the tool is within its limit. Yes leads to use it and record the check. No leads to re-zero and re-check, then a second decision: if the tool is now within its limit, use it and record the check; if it is still out, tag it out and report it, then calibration with a certificate giving value and uncertainty, then back in service with a record kept.

A teaching sequence built from the makers' guidance and NIST's calibration vocabulary; it is not an AFS procedure.

Sources

Videos for this lesson

What this video shows: Mitutoyo's own demonstration of the steps for reading a standard micrometer or a vernier micrometer. Checked against the video's description.

Video: How To Read A Mitutoyo Inch Vernier Micrometer by Mitutoyo America Corporation, on YouTube. Chosen from the video's published description.

What this video shows: Mitutoyo's own product demonstration of using vernier calipers. Checked against the video's description.

Video: Vernier Caliper Use from Mitutoyo by Mitutoyo America Corporation, on YouTube. Chosen from the video's published description.

Glossary

Parallax
The apparent shift of a reading when a scale is viewed at an angle. Mitutoyo says to look directly at the vernier or fiducial line when reading.
Thimble
The rotating barrel of a micrometer. On an inch micrometer it has 25 divisions of .001 in, and one full turn moves the spindle .025 in (Starrett).
Vernier protractor
A bevel protractor whose vernier has 12 divisions of 5 minutes each, so it reads to 1/12 of a degree (Starrett 359).
Reference length
A length whose true value is known well enough to compare a tape or rule against. Checking against a reference tells you more than comparing two tapes.
Flip test
A check that reverses a square or level and repeats the mark or reading: if the two results differ, the tool is out. Flipping mirrors the error, so by geometry the gap shows twice the error.