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  • Metal Thickness vs Gauge

    The thread on metric reminded me of another pet peeve.
    Is there a logical explanation for the various 'gauge' names for metal sheet.
    One reference shows 16 gauge = 0.0598 for uncoated steel sheet, 0.0635 for galvanize coated [but how thick is the galv coating -- in the steel mill it's speced in grams per square meter separately for each side of the steel?] and 0.0508 for aluminum.
    We won't even look at copper, brass sheet or electrical wire sizes for now.
    I worked for 40 years in a steel mill on the xray gauges that were the 'feedback' on rolling mills that controlled the final thickness of the sheets & plates.
    In all that time I NEVER saw a thickness gauge, manual or computer, set up by a gauge number, only in DECIMAL thickness.
    Guess that's why I have a bookshelf of Machinery's Handbooks and supplier catalogs!

    John in NW Indiana
    Last edited by JohnHarbeck; 05-01-2013, 11:56 AM.

  • #2
    Originally posted by JohnHarbeck View Post
    One reference shows 16 gauge = 0.0598 for uncoated steel sheet, 0.0635 for galvanize coated [but how thick is the galv coatring?] and 0.0508 for aluminum.
    John in NW Indiana
    I don't know myself, But that has always buged me too. I can almost understand the extra size for galvanized because its weaker surface coating and you would want '16ga of steel', but why the heck is aluminum thinner??
    Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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    • #3
      Interesting question John, looking to see the responses to this question.

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      • #4
        Up through the early 20th century, every industry had its own gauge system. And they were usually different for different metals - 20 gauge brass was a different thickness than 20 gauge iron, for example.

        Most of them originated in Britain at the dawn of the Industrial Revolution, when "standard" meant "whatever Nigel has been doing lately."

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        • #5
          Basically, each company invented their own standards. Thus you have the Washburn & Moen wire gauge, the Stubbs wire gauge, etc. Likewise, the Morse Twist Drill Company invented Morse tapers, Brown & Sharpe invented B&S tapers, and so on. Industry-wide standards hadn't been conceived of yet. Eventually, smaller companies dropped out, or chose to adopt the standards used by the dominant companies in the various industries, so today we are left with the survivors, and virtually none of the gauges make any logical sense. They are just what various companies came up with back in 1875, or whenever it might have been.
          ----------
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          • #6
            The gauge for aluminum is it's actual thickness. It was at Kaiser anyways.
            Gene

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            • #7
              The only thing 'gauge' does for me is test my memory- see if I can remember how thick that is in thou-

              I wonder how they talk about it in sheet metal shops- somebody says 'hey, help me with this sheet of 16 gauge', or do they say 'help me with this sheet of oh five nine'
              I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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              • #8
                Originally posted by darryl View Post
                The only thing 'gauge' does for me is test my memory- see if I can remember how thick that is in thou-

                I wonder how they talk about it in sheet metal shops- somebody says 'hey, help me with this sheet of 16 gauge', or do they say 'help me with this sheet of oh five nine'
                The metal shop I went to had it in decimal till about 0.041" iirc? And then went to gauge (for 8 to 14ga or so, then went to fractional inches)
                Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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                • #9
                  This thread brings up a pertinent thing to a project at school. The material in
                  question is hot rolled steel. Dwg. calls 1/8" but the only things I can find in
                  the stock measures either 0.130 or a bit over 0.100" (varies from about .105
                  to .115 ) So what gauge are they? Making something out of this plays the
                  vary devil with trying to maintain tolerances on other parts. :-(
                  ...lew...

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                  • #10
                    Here are a few pieces of the answer:

                    The legal definition of Sheet Steel Gauges is from 15 USC § 206 - Standard gauge for sheet and plate iron and steel.

                    Some history of how we got to the current gauge sizes and thicknesses can be read from Steel Market Update Manufacturers Standard Gauge History.

                    A list of the Manufactures Standard Gauge thicknesses can be viewed HERE

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                    • #11
                      And if you really want to do something easily, just use decimals and ditch the gauges (applies to all gauge systems).
                      Amount of experience is in direct proportion to the value of broken equipment.

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                      • #12
                        In all the metal shops I worked steel went by gauge , aluminum by thickness .025 .032 .040 and so on and copper by oz. per sq. ft. with 16oz. the most common. At the time it never seemed odd.

                        Stu

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                        • #13
                          Originally posted by JohnHarbeck View Post
                          The thread on metric reminded me of another pet peeve.
                          Is there a logical explanation for the various 'gauge' names for metal sheet.
                          One reference shows 16 gauge = 0.0598 for uncoated steel sheet, 0.0635 for galvanize coated [but how thick is the galv coating -- in the steel mill it's speced in grams per square meter separately for each side of the steel?] and 0.0508 for aluminum.
                          We won't even look at copper, brass sheet or electrical wire sizes for now.
                          I worked for 40 years in a steel mill on the xray gauges that were the 'feedback' on rolling mills that controlled the final thickness of the sheets & plates.
                          In all that time I NEVER saw a thickness gauge, manual or computer, set up by a gauge number, only in DECIMAL thickness.
                          Guess that's why I have a bookshelf of Machinery's Handbooks and supplier catalogs!

                          John in NW Indiana
                          John - let's see what the defenders of the good old imperial system system have to say on this.
                          So let's hear from you and how you defend the use of all these gauges. After all it is rooted in our industry for generations. How much superior is this to calling for a 3mm sheet of plastic, steel, copper etc. etc..

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                          • #14
                            My understanding is that in the early days gauge was defined by the number of passes through the mill that it took to produce it. Thus the more passes the larger the gauge number and the thinner the steel. Of course the setup of the mill would influence this and it would be different from one manufacturer to another.

                            This gauge number is now probably maintained just to confuse people and to execise apprentices.



                            Ken

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                            • #15
                              Originally posted by TriHonu View Post
                              Here are a few pieces of the answer:

                              The legal definition of Sheet Steel Gauges is from 15 USC § 206 - Standard gauge for sheet and plate iron and steel.
                              A whole lot of good that does without tolerances. :-( So my 0.130" is "Probably " 1/8" but sure is more than a bit oversize. You'd think the bean counters would insist the tolerances would be on the thin side. :-)
                              ...lew...

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