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# Sheet metal gauge calculation

## Sheet metal gauge calculation

#1
05-04-22, 03:38 AM
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Sheet metal gauge calculation

I needed 24 gauge or thicker sheet metal for a rodent barrier and used two sheets of 30-gauge. The exercise I went through to figure out if doubling 30-gauge sheet metal would work involved converting 24 gauge to mm (.701 for galvanized), then finding the gauge needed to reach it - at least 31 gauge, doubled.

This got me wondering if there's a formula for comparing gauge without having to convert it to something else. Any help would be appreciated.

05-04-22, 12:08 PM
Norm201
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Yes! Metric!

#2
05-04-22, 04:50 AM
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Why use a formula? Just look at any of the MANY charts available online and in books.

cwbuff voted this post useful.
#3
05-04-22, 05:51 AM
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Dane, I don't disagree as that's what I did. But I assume there should be a formula. I doubt if gauge is arbitrary.

#4
05-04-22, 06:49 AM
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Actually I think it is. A quick glance did not seem to show any mathematical ratio or type of relation between the thicknesses. However there is a formula that explains how a gauge is determined in terms of weight vs thickness as can be shown at this web site:
How to Calculate Steel Gauge to Inches (sciencing.com)

But I don't see any relation between thickness. But the numbers, though may be arbitrary, they are set in stone. In other words a 29 gauge sheet of metal is not determined by the thickness of the preceding gauge of 28.
I might be wrong!

#5
05-04-22, 08:56 AM
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One story I've heard is that "gauge" came about at the beginning of the industrial revolution. Wire was one of the first forms/shapes of steel. Ordering by weight was easy but how do you specify what diameter wire you want. So they term "gauge" came about from the number of times they drew/stretched the wire. The more stretches/gauges the smaller/thinner the wire became. Then later in they started flattening wire into sheets and the term gauge stuck. That's why larger numbers are thinner (opposite of what you'd expect). Why there isn't a direct formula or ratio between gauges. And why gauge thickness varies depending on the material. Makes you want to adopt the metric system doesn't it.

CircuitBreaker voted this post useful.
#6
05-04-22, 12:08 PM
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Yes! Metric!

Marq1 voted this post useful.
#7
05-05-22, 03:12 AM
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This turns out to be more interesting (to me) than I expected. Dane, based on your post I did some research on the history of gauge. I came across an article from the Association of Anaesthetists. It seemed like an unusual place but apparently gauge is used in needle specs.

Gauge goes back at least to 1200 in Germany. It seems gauge related to the draw of wire through a hole to narrow it. Each draw would narrow the wire, which is why gauge is higher for smaller diameters. While this article addresses gauge for wire, it doesn't fully address sheet metal which, I think has a different history related to weight.

For anyone interested in gauge as much as I was, here's the article.
https://associationofanaesthetists-p...4.1999.00895.x

#8
05-05-22, 04:32 AM
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​​​​​
Yes! Metric!
As I have stated before, English units are used by the thee super powers of the world, The United States of America, Myanmar, and Liberia.

What kills me, at work we make a lot of prototype parts to support the engineering organization. Everything is designed in metric and engineers are shocked when they cant get their parts fabricated to the material thickness as designed and have no idea that sheet metal is only available in standard gauge thicknesses.

​​​​​​​And these are degreed engineers!