Gauge thickness and material weights · Lesson 1 of 4

Gauge thickness and material weights: principles and terminology

What "24 ga", ".040", "16 oz" and "0.7 mm" each mean, why gauge runs backwards, where the gauge system came from, and why a decimal thickness belongs on every order.

You will be able to: Explain why a gauge number is not a thickness until a table is named, define gauge, weight gauge, nominal and decimal thickness, and name the four units AFS uses for sheet.

9 min · 10 slides · 7 questions

All lessons in this module

Slide 1 of 10

Why thickness matters

Thickness sets the weight of every piece and the bend rules AFS applies to it.

At AFS, steel at 18 gauge and heavier is bent once only, with no hems.

This module teaches how to read a thickness off an order, work out a weight and check the stock that arrives.

Sources

AFS fabrication limits - materials, thicknesses, bend rules and sizes the shop can make - Architectural Flashing Supply

Videos for this lesson

What this video shows: A Sheffield Metals Q&A episode. Its description says steel, aluminum, zinc and copper are measured in different units and lists chapters on gauges, thickness against gauge and aluminum. Checked against its description only; its numbers are not used in this module.

Video: How Is Metal Roofing Thickness Measured? Gauges, Inches, Ounces by The Metal Roofing Channel, on YouTube. Chosen from the video's published description.

Glossary

Gauge: A number that stands for a sheet thickness in one named table. A higher number is thinner steel, and the same number is a different thickness in different tables.
Weight gauge: A gauge defined by the weight of a square foot of sheet. The 1893 U.S. Standard Gauge is one: No. 24 is 16 oz per square foot.
Nominal thickness: The table or ordered thickness, such as 0.0276 in for 24 gauge galvanized. Real sheet varies a little either side within its tolerance.
Decimal thickness: A thickness written in inches, such as 0.040 in, instead of by a gauge number. AFS sells aluminum this way, and the decimal is the size.
Ounce weight: How copper sheet is named at AFS: 16 oz means a square foot weighs 16 oz, which is 1 lb.