I was looking at a Harbor Freight catalog for a shear and was wondering what gauge (thickness) meant. I looked up gauge in Wikipedia and noticed that the same gauge (for example 22 gauge) is different for various types of metal.
This seems really stupid. Who thought up of this inane system?
gauge thickness is a relative term to metal and others.
Example - my son, who’s diabetic has a 32 gauge thickness needle. I want something smaller for him since he’s still so little. So I ask my med privider for a 34g needle.
Seems counter-intuitive, but the higher the gauge, the smaller the width and diameter. Hope this helps.
That relationship also applies to craft wire. Checking my own supplies, 20ga is substantially thicker than 28ga.
I doubt the system was designed, it just sort of happened. Different crafts came up with scales for different metals as it was needed for them. There is no single, unified system.
Right, but that’s not the OP’s question. I presume he knows that larger number gauge is actually thinner. (I believe that stems from early wire and sheet metal manufacturing, where thinner materials were produced by more passes through a die. More passes = thinner = bigger gauge number).
Rather, why is there difference between material types? 10 gauge sheet metal is 3.42 mm thick for steel, 2.59 mm for aluminum, and 0.51 mm for zinc (from the OP’s wiki link).
Like the OP, my reaction is “WTF?”. Why not have comparable measurements between materials?
My guess, until someone who knows comes along, is that softer metals compress more each time through the roller, and the gauges would be farther apart for softer metals. Another factor could be that some metals allow more compression each roll without harming the atomic structure.
Either way, the process is going to be dependent on the properties of the different metals, which of course vary a lot. Working to achieve a single set of standard thicknesses would be more difficult, and could be less efficient.
it’s based on the weight of the material
Via some links in the wiki article I found a email address to a professor at University of North Carolina. I emailed the question to him with a link to this thread.
Cross your fingers.
I saw that but I don’t know if the difference in thickness between steel and aluminum of the same gauge is enough to account for the difference in weight.
Electric wire varies a lot. Lamp cord is 18 gauge. Very cheap extension cords are 18 gauge. Better quality ones are 16 gauge.
House wiring is 14 gauge for switches and 12 gauge for wall receptacles. A kitchen range has a *huge *8 gauge wire.
The whole purpose of the system is to enable you to easily calculate the weight of material, and thus cost, for your project. It says so in the linked wiki article.
If the thickness were the same for each metal, you’d also have to have a multiplier for each metal before you could find the weight. This system saves that step, and a need for a list of multipliers for different metals.
Sheet aluminum is heavier than sheet steel per mm of thickness?
As a person who works with sheet metals (copper and pewter) i am heartily confused by sheet metal gauges, there are American gauges and UK gauges, with the addition of wire gauges. I usually plead ignorance and say the ones that very nearly 1mm thick.
Wire gauges such as syringe needles might be is different again, its based on how many of the wires can fit through a certain sized hole hence they go up as they are thinner…
Question, about gauges, but not sheet metal ones.
Since the gauge of a shotgun is based on how many lead balls of the same diameter as the shotgun barrel would be required to weigh a pound (except of course for a .410), what term do the Europeans use to describe the size of a shotgun? For instance, what would they call a 20 gauge shotgun?
Yeah, that’s what I meant. You would think there would have been some sort of brilliant engineer who they could have named a linear measurement unit like Wolfgang Millimeter or Leonardo da Vinci and called the measurement a Davinci or a Lict or something like that.
Also, is it spelled gage in the UK?
OK, Cheshire Human’s comment makes sense, in a ridiculous kind of way. I suppose the various tiny fractions of inch would be pretty cumbersome to use. I guess since plastic is a fairly recent invention, someone came up with the brilliant idea of using mils for thickness.
And I guess since metal is standardly manufactured in integral gauge sizes, there’s too much infrastructure to change. I remember that the Tupolev TU-4 was copied from the B-29 and it was a real bitch because of the difference between Russian and American sheet metal thickness.
Though from the linked Wiki article (and other Google hits) zinc is on a different scale with thickness increasing with gauge. 
:smack:
20 Bore
How does it do this?
Look at 10 gauge: Stainless is 3.57 mm thick, and Aluminum is 2.59 mm thick. Is Stainless 28% lighter than Aluminum? In 18 gauge, stainless is 1.27 mm thick and Aluminum is 1.02 mm thick. Is stainless now only 20% lighter than Aluminum? In 20 gauge, stainless is 0.95 mm thick and Aluminum is 0.81 mm thick. Stainless now 15% lighter than Aluminum?
There’s no simple correspondence like you’re thinking. If you’re using gauge number to get weight, you need a list of multipliers for each metal and gauge.
So they are still using a measurement based on the Imperial system. Some things are still right in the world.
1" = 1g = 1.000 in.
1/16" = 16g = .0625 in.
It drops up and down about a 0.5 millimeter or a .015" per scale…roughly.
But, anything over 1/8 =.125 becomes plate, then you ask for 1/8" plate steel or aluminum.
Also, If you buy 0.040" aluminum…its 0.040" measuring with a micrometer. Which is about the same as 1 MM = 0.0397.