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Gauge thickness and material weights · Lesson 4 of 4

Gauge thickness and material weights: defects, verification and case study

The common thickness and weight mistakes, how big each one is, a worked case of delivered sheet that is thinner than its tag, and the record a reviewer needs.

You will be able to: Spot a wrong table, a mislabelled or thin sheet, a missing unit or an unstated weight basis, size the error it causes, and record the evidence for a review.

8 min · 10 slides · 6 questions

All lessons in this module
Slide 1 of 10

Defects to look for

Most thickness and weight errors come from one of these:

  • The wrong table for the material
  • Stock thinner or thicker than its tag
  • A gauge number on an aluminum order
  • A thickness with no unit
  • A weight with no stated basis
  • Heavy steel on a profile it cannot take
Correct and incorrect ways to write thickness and weightFive pairs. Write 24 ga galvanized with 0.0276 in, not 24 ga alone. Use 1.156 lb for the galvanized piece weight, not the uncoated 1.000 lb. Order aluminum as 0.040 in, not 24 ga aluminum. Write 0.7 mm with its unit. Take three readings and check each against the band, not one reading.CorrectIncorrect24 ga galvanized,0.0276 in"24 ga" alone15 sq ft x 1.156 lb= 17.34 lb15 sq ft x 1.000 lb= 15.00 lb (wrongcolumn)Aluminum 0.040 in"24 ga aluminum"0.7 mm (0.0276 in)"0.7" with no unitThree readings,mean 0.0270 in,all in bandOne reading,no band

Five pairs. Write 24 ga galvanized with 0.0276 in, not 24 ga alone. Use 1.156 lb for the galvanized piece weight, not the uncoated 1.000 lb. Order aluminum as 0.040 in, not 24 ga aluminum. Write 0.7 mm with its unit. Take three readings and check each against the band, not one reading.

Five habits that stop most thickness and weight errors. The weights use the AFS register for galvanized and the sheet-steel column of a distributor chart for the incorrect case.

Sources

Videos for this lesson

What this video shows: A 34 second product demo from the maker. Its description says a sheet metal micrometer measures the thickness of sheet metal where a deep-throat micrometer is required. Checked against its description only.

Video: Sheet Metal Micrometer Demo - Mitutoyo America by Mitutoyo America Corporation, on YouTube. Chosen from the video's published description.

Glossary

Mislabelled stock
Sheet whose measured thickness does not match the gauge or size on its tag, for example 24 gauge galvanized that measures 0.0220 in against a 0.0236 in minimum.
Under-thickness
A measured thickness below the minimum of the tolerance band for the ordered size, such as under 0.0236 in for 24 gauge galvanized.
Receiving check
Measuring delivered sheet with a micrometer, three readings on flat sheet, and comparing each reading and the average with the tolerance band for the ordered size, as set by the order or mill certificate, before the sheet is formed. The three-reading routine is a teaching convention in this course.
Mill certificate
The maker's document for a coil or sheet lot. Ask the supplier for it when delivered stock does not match its tag, and use it to confirm which table applies.