No Inch Fractions for Chainmaille – Use Metric

2 09 2013

If you are going to get good at making chainmaille, you will end up doing math. You can do it the hard way by using inches and fractions of inches, or you can do it the easy way by using decimals and millimeters, i.e., metric system.

Note to people who make chainmaille tutorials and provide instructions: Make it easy on people, please! USE METRIC!

If math is not your “thing,” then this post IS probably for you. Sure, it has a lot of numbers and formulas, but I’ll walk you through them and tell you what they mean. If you are not careful, your math skills might actually improve! If you learn anything from this post, learn that chainmaille is easier when you use metric.

Problems with Fractions of Inches

Inches and fractions are hard to use when you’re making chainmaille, especially when you need to calculate aspect ratio. For example, let’s say you read a chainmaille tutorial that tells you to use rings like this:

inside diameter of the ring: 5/16

wire diameter (gauge): 1/32

Now you need to calculate the aspect ratio. Remember that aspect ratio is

Inside diameter / gauge = aspect ratio OR ID / GA = AR

So, using the sample ring details, here’s your formula:

(5/16) / (1/32) = AR

If you like dividing fractions (who does?), you could do this:

(5/16) / (1/32)  = (10/32) / (1 / 32) = (10/32) / (1/32) = 10 / 1 = 10 AR

But why would you want to do that? Even if your math skills are pretty good, like mine, fractions are a nuisance. Why not just divide numbers? This means…

Use metric.

After all, wire is typically sold with gauge in metric units, such as

20 gauge AWG = 0.81 mm

18 gauge AWG = 1.02 mm

See? No fractions. When the ring diameter is in fractions of inches, not only do we need to deal with the fraction but we also need to deal with using 2 different measurement systems!

Typical Problem with Fractions

Now, here’s a typical case I run into. I find a JPL tutorial that says use 20 gauge AWG wire with 3/32 inch inner ring diameter. I want to make the chain larger but keep the same proportions, so I need to figure out the aspect ratio. What’s the aspect ratio of the rings in the tutorial? Here’s the formula:

(3/32 inches) / 0.81 mm = ???

Well, 20 gauge is 0.032 inches in diameter, so maybe I get lucky, and the tutorial says 3/32 inches inner diameter and 0.032 inches wire gauge. At least this stays in one measurement system: inches. But it still has that pesky fraction. Too bad they didn’t…

Use metric.

In metric measurements, the tutorial would say

2.38 ID with 20 gauge (not 3/32 inches ID with 20 gauge)

Ahh. That’s so much easier. Even if I’m using a calculator and not doing it in my head, it’s less complicated to calculate because I don’t have to convert the fractions to decimals first.

Convert to Metric and Make Everything Easier

When you run into tutorials that use fractions, just convert everything to metric. It’s simple to do. Here’s how.

a. Take your fraction

3/16

b. Convert to a decimal

3 / 16 = 0.1875 (3 divided by 16 = 0.1875 of 1 inch)

This is 0.1875 of 1 inch, right. Well 1 inch = 25.4 mm. (Remember this number: 25.4. It’s the most important number of the entire process!) So, if you need 0.1875 of 1 inch, you also need 0.1875 of 25.4 mm, because 1 inch is the same as 25.4 mm.

c. And multiply by 25.4

0.1875 x 25.4 = 4.76 mm

When we condense these steps we get

3 / 16 x 25.4

In words, Divide 3 by 16 and multiply by 25.4.

If the fraction was 5/32, then you would divide 5 by 32 and multiply by 25.4, which gives you 3.97 mm. You can round this to 4 to make the math even easier! This is close enough to 4 that it won’t matter, because 0.03 mm makes almost no difference to chainmaille.

Now, you have the ring inner diameter in millimeters, you have gauge in millimeters, and the math just got a lot simpler!

Let’s go back to that JPL tutorial that used 3/32 ID and 20 GA.

To get the AR, we will convert the ID to millimeters and divide by the GA. Thus…

3 / 32 x 25.4 = 2.38

2.38 / 0.81 = 2.94 AR,

(By the way, 2.94 is quite lovely for JPL!)

In condensed form, we did this:

3 / 32 x 25.4 / 0.81

3 divided by 32 gives us the decimal. Multiplying by 25.4 gives us millimeters for the inner diameter. Dividing the inner diameter by the wire diameter gives us the aspect ratio.

2.38 mm is a lot easier to use, and to visualize, than 3/32 inches. And it’s a lot easier when you need to do the math. Of course, this would all have been much, much simpler if people who write tutorials would just…

Use metric!

Summary of the Formulas

Aspect ratio: Inner diameter divided by wire diameter, using the same measurement system for both measurements: ID / GA

Inch fraction to millimeters: top number divided by bottom number times 25.4: a / b x 25.4

Inch fraction to aspect ratio: top number divided by bottom number times 25.4 divided by wire diameter: a / b x 25.4 / GA

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One response

12 11 2016
Erika Doss

The suppliers I buy from list the AR, and don’t sell rings in metric. Yeah, if you’re making your own rings it would be a nuisance. Not all of us want to make rings though. Most of the suppliers I’ve seen that sell in metric, do not list the AR. This means that metric is much more of a nuisance for me. Since, not all rings marked the same size have the same AR, I would first have to measure and then compute the AR. No thanks, I’ll keep my fractions.

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