The aspect ratio (or AR) is a way of describing how thick/thin a ring is. This is desperately important to chainmaillers because not all weaves use the same size rings. Let me repeat that, since it’s really important… Not all weaves use the same size rings. Here are a couple weave examples to show you why that statement is quite so important. I’ll use Full Persian and Birdcage for these examples because Full Persian likes a very thin ring and Birdcage likes a very thick ring.
Our two rings. On the left is a “hula-hoop” ring. Its inner diameter is large compared to its wire thickness. On the right is a “chunky-monkey” ring. Its roughly the same overall size, but much sturdier.
Full Persian weave made with both rings. It works really nicely with the hula-hoops, but we run out of room almost immediately with the chunky-monkeys. Full Persian requires each ring to pass through six other rings, and the path that they follow is pretty complex. Hula-hoops are great for that sort of weave, but chunky-monkeys are too crowded.
Birdcage (AKA Byzantine) weave made with both rings. While it is possible to make the weave with both types of ring, the chunky-monkeys look a lot better. Birdcage prefers rings that will take up enough space to make the pattern hold steady. Chunky-monkeys are great for that sort of weave, but hula-hoops look messy.
Now that I’ve convinced you that each weave has its own idea of “perfect” ring size, we need a way to say whether a particular ring is like a hula-hoop, like a chunky-monkey, or somewhere in between. The aspect ratio (AR) of a ring is a single number that describes the thickness/thinness of that ring size.
aspect ratio = inner diameter ÷ wire diameter
For the example rings that I used, the AR of the hula-hoop is 5.17 and the AR of the chunky-monkey is 3.41. The higher the AR, the thinner the ring. It doesn’t matter what the overall size of the ring is, what’s important is the comparison of ring diameter to wire diameter. The AR will be the same for a perfect Birdcage ring no matter whether that ring is a couple millimeters wide or a couple inches wide.
You can use that relationship to figure out any of the pieces if you know the other two. You can dust off your high school algebra, or you can just use this “cheat triangle.” If you stick your thumb over the thing you need to know, whatever is left visible tells you how to find it. (My thanks to Jim for this wonderful adaptation of the Ohm’s Law Triangle. The idea is entirely his.)
So what does all this mean to you? Since each chainmail weave has an ideal AR, you can now take some of the guesswork out of what size rings to make/buy. Let’s look at a few examples…
You know the weave and the wire size, but you don’t know the inner diameter.
ID = WD x AR
You’re making Birdcage (ideal AR of 3.5) and you’re using 18ga wire (0.040″). You don’t know what would be the best inner diameter for your rings. Multiply the wire diameter by the aspect ratio. 0.040″ x 3.5 = 0.14″ which is very close to 9/64″.
You know the weave and the inner diameter, but you don’t know the wire size.
WD = ID ÷ AR
You’re making Full Persian (AR of 5.25) and you want the rings to be 3/16″ (which equals 0.1875″). Divide the inner diameter by the aspect ratio. 0.1875″ ÷ 5.25 = 0.0357″ which is 19ga (or really, really close anyway).
You just found some mystery rings. What should you make with them?
AR = ID ÷ WD
When you measure your rings, you find that the wire is 1.3mm thick and the outer diameter is 7mm. Subtract two wire thicknesses to determine that the inner diameter of these mystery rings is 4.4mm. (Yes, you can measure the inner diameter directly, but I find it easier and more accurate to do a little subtraction.) Divide the inner diameter by the wire diameter. 4.4mm ÷ 1.3mm = 3.38, which is a reasonable size for Birdcage, European 4-in-1, and Turkish Round.
Aspect ratio is a profoundly useful concept. There are so many weaves out there (more every day!) and being able to figure out for yourself what rings to use is really helpful.
If you browse the family portraits for various weaves, you can see the aspect ratio in action. All the sample chains are made with rings of the same AR, even though the overall size of the chain varies dramatically with gauge.
If you’d like some hands-on experimenting, I recommend one of the AR samplers – 22ga through 10ga rings with the same aspect ratio.
And finally, the lazy method! I encourage you to calculate at least a few aspect ratio manually, to help the concept stick in your memory, but after that… I use an Excel spreadsheet to answer Aspect Ratio questions. (Life is too short for repeated trips to the calculator!) Please download a copy for your own use and amusement: spiderchain_AR.xlsx (last updated October 23, 2015)
If you want a quick reference, you can tap/click for a larger version of the picture on the right. It’s just a screenshot of the “proper” spreadsheet, complete with color flagged European 4-in-1 sizes. This grid will be miserable to browse on a phone, but it’s better than nothing at all! *grin*
The aspect ratio is a wonderfully useful concept. I hope this explanation helps you understand how to use it!
I have a commission to make some jewelry from medical implants harvested from the cremains of my customer’s partner. I have several pieces of ~16g wire – the customer saw a box chain bracelet I made and wants me to make the wires into jump rings and then make a box chain bracelet.
While you have some great charts on your site, I am unable to find the conversion/info I need to make the rings the correct size. Could you please help?
Box chain ideal AR = 5.1 (right?)
Wire gauge I have = 16g or 1.3mm
what MANDREL size do I need to use to make rings with an appropriate AR for the box weave?
Short answer? You should be good with a 6.5mm mandrel, or possibly a 6.25mm mandrel. If you’re working in inches, use a 1/4″ mandrel.
And now the (much) longer answer. You can either:
1) Do the math based on what you know about AR
2) Look at the charts of Spider Approved sizes
Option 1 – Math
I’ll go through the calculation first, but there are some details having to do with wire springback that you should also consider.
You’re trying to find the ID, which means that we should look at Example 1, above.
ID = WD x AR
WD = 1.3mm
AR = 5.1 (correct, but read more below)
ID = 1.3mm x 5.1
ID = 6.63mm
Now here’s where things get interesting… I agree that an aspect ratio of 5.1 is good for Box Chain, but only if you’re talking about post-springback measurements. When you’re making rings, you wrap wire tightly around a mandrel to bend it into circles – but when you let go of the wire? It goes “sproing!” and the coil loosens up a bit. That loosening is called springback, and it’s different for each material. The harder the wire, the more it sproings and the larger the coil comes out in the end. Wire hardness varies by material (steel is harder than gold) and also by wire temper (spring-hard is harder than dead-soft).
Post-springback aspect ratio is based on the actual measurement of the ring that you’ll be using. It’s a wonderfully accurate way of describing the ring, and it means that people working in spring-hard steel can easily compare notes with people working in dead-soft gold. But “accurate” isn’t always the same thing as “convenient.” You’ll need to wrap your wire around a mandrel that’s a little smaller than 6.63mm if you want your rings to be the right size after springback. But how much smaller? The rule of thumb I use is to start with the nearest mandrel size below my target ID. I often (but not always) end up dropping one more mandrel size after that. So in this case, with a target ID of 6.63mm, I’d start with a 6.5mm mandrel. If I were working in inches (target of 0.261″), I’d start with a 1/4″ mandrel.
That said, I’ve tested Box Chain pretty extensively – I know that 6.5mm is actually a bit looser than I like for a 16ga Box Chain (6.25mm is better). In inches, 1/4″ works great. In this case, I did drop an extra mandrel size for the millimeters, but not for the inches.
Please remember that the testing I do is with my wire, which is all roughly the same hardness as half-hard sterling silver. If your wire is at least as hard as half-hard sterling, then you could theoretically use the 6.25mm mandrel as well. But if you think that your wire might be softer, I’d recommend you stay with the (slightly looser) 6.5mm size. The wire that you’re using is unique. If your weave is a smidge too tight, you can’t just order more wire and bump up the ring size. Box Chain that’s a smidge loose is still lovely. Box Chain that’s a smidge tight doesn’t move well. Play it safe!
Option 2 – Charts
You can skip a lot of the math and fuss by going straight to my size charts. You know you’re working in 16ga wire, so you’d see that the size recommendation for Box Chain is either 16:16 (if you’re working in inches) or 6.25M16 (if you’re working in millimeters). If you’re not sure what my ring names mean, there’s a full explanation on the FAQ page, but the simple version is that the first number is the mandrel size and the second number is the wire gauge. A colon in the middle means that you’re looking at an inch size, so that first number is in 64ths of an inch. An M in the middle means that you’re looking at a millimeter size, so that first number is in millimeters.
16:16 means 16/64″ mandrel (same thing as 1/4″), 16ga AWG wire
6.25M16 means 6.25mm mandrel, 16ga AWG wire
The size chart is definitely the fastest way to find an answer, but it’s useful to understand that those recommendations are only going to work for wire that’s comparable in hardness to the wire that I use.
As long as I’m being so long-winded… One more thought…
When I’m testing weaves, I keep notes about which pre-springback aspect ratios work well. All my wire is roughly the same hardness, so I can be a little “lazy” about my AR calculations and just use mandrel size for the inner diameter. I know that my calculated pre-springback AR will always be smaller than the measured post-springback reality, but it will be roughly the same amount smaller across all my materials – so it’s safe for me to use when guessing at a new size. So convenient!
You can find that pre-springback AR in the downloadable spreadsheet above. And just for fun, I’ve added a screenshot here of my favorite Box Chain sizes flagged in blue. You can also look up the AR of a specific ring size in the build-a-ring tool.
I’ve been quite confused by the aspect ratio since starting chainmaille jewellry a few years ago. This was really helpful and made it really easy to understand. Thanks so much!
I need help in finding out the aspect ratio to make a Moscow chain I have 16 gauge 18 gauge and 20 gauge but I need to know what the aspect ratio should be
I wasn’t familiar with “Moscow chain” so I did an image search and came up with a chain that looks like it was run through a rolling mill after it was made. Is that the chain you mean? If so, then you’ll need to find a different chain-maker to help you with ring sizes. I’m pretty good at the “squint estimate” for aspect ratio, but not for chains that are hammered/rolled/squashed after they’re woven. Sorry I couldn’t be more help! (And if the “Moscow chain” that you’re referring to is a straight chainmail weave, then please reply here with more information and I’ll give it another look.)