“Gauge” is a relative measurement, specific for each item. Some items measure relative thickness (roofing sheets, steel sheets), relative diameter (wire, pipes) etc etc. For example, gauge-24 roofing-sheets are pretty thick (and inflexible/stiff), gauge-30 are much, much thinner than the 24, and gauge-32 get thinner and very flexible. It is not an exact measurement “unit” per-se.
Some units of measurement are standardized–for example the SI or ‘metric’ units which are all based on a physical standard–and other units are not standardized, but instead are used because of tradition or industry standards.
Gauges as used in firearms and wire gauges are units that originate in tradition and have become more standardized by industry. American Wire Gauge numbers, for example, were originally based on the number of times a wire had to be pulled through smaller and smaller sized die holes to achieve a certain thickness (ergo, a very small wire has a high ‘gauge’ because it had to be processed a higher number of times to make it small).
Needle sizes are based on the size of the hole in the tip of the needle while the ‘gauge’ of the needle can vary from manufacturer to manufacturer based on which needle gauge system they are using–because unfortunately there is more than one.
To make things even more difficult, now some types of ‘gauge’ are a logarithmic unit which basically just means you are numbering certain intervals of a mathematical curve or exponential change.
There have been attempts to standardize units of measurement, but it is almost always resisted by industry as it necessitates some cost in changing from one measurement to another for ‘no reason’ as the money hungry capitalist overlord pigs would describe it anyway.
Gauge means different things in different context.
Shotgun gauges – and less commonly rifle bores – are simple, as they tell you what weight of lead ball you could theoretically load it with. 1/x lb ball, where x is the gauge/bore number. E.g. a 12 gauge shotgun has a barrel wide enough to fit a 1/12 lb lead ball, and a 4 bore rifle can be loaded with a 1/4 lead ball. Such measurements are useful if the projectile being fired is a lead ball, but are less useful nowadays as few people use muskets.
Needle gauges are based off of wire gauges, which were determined by convenience. Needle gauges, like shotghn gauges, tell you how wide the opening is, and all three mentioned this far, decrease over diameter as gauge number increases.
Railway gauge measures distance between tracks. Unlike the three other gauges mentionedthis far, larger numbers do not mean greater track seperation. Rather, railway gauge is simply expressed as the distance between tracks, whether that be metric or imperial. Standard gauge is commonly held to be 1435mm or 4ft 8.5inches.
Y’all are really going into the weeds on shotgun gauges. Shotgun gauge is hillbilly math.
Shotgun gauge is determined by how many lead balls of that barrel diameter would equal one pound. A lead ball with the diameter of a 12 gauge shotgun barrel would weigh 1/12 of a pound.
This is why shotguns with smaller barrels have a high gauge. A 20 gauge shotgun would require 20 lead balls to equal one pound, while a 10 gauge shotgun would only require 10 lead balls to equal one pound (because the barrel is roughly twice the diameter of the 20 gauge).
Gauge is funky because it’s like an inverse measurement. The larger the value, the smaller the item. As /u/TheJeeronian stated, for shotguns, it’s “how many of X would you need for Y”. If you needed 12, then those are going to be larger than if you needed 18, but smaller than if you only needed 8.
This applies to holes and diameter of wiring fitting into holes. The higher the value of the wire, the thinner it is…because you’d need more wires to fit into X fixed amount of space.
Therefore, 12 gauge of one thing is different than 12 gauge of another, because the fixed measurement (1 pound of lead, 1 inch, etc) changes per application of the measurement.
Latest Answers