Tips on Measuring Jump Rings for Chain Mail
How To Calculate the Inside or Outside Diameter of Jump Rings
I'm teaching a Chain Mail (aka "Chain Maille") class this weekend so I thought it would be a good opportunity to delve into the fascinating world of jump ring measurement. Caution, math ahead!
Measuring jump rings seems like it shouldn't be all that complicated. However, if you are excited about chain mail and want to go a little deeper into the craft, you'll find that not everyone measures jump rings the same way. This overview should help alleviate some of the confusion.
First let's talk about the anatomy of a jump ring.
Essentially a jump ring is a piece of wire that is formed into a circle. There is a cut present by which you can open and close the ring. (Other jump rings used in jewelry making include "split rings" and "soldered rings," but we'll cover those another time.) The thickness of the wire is called the gauge. Lastly. you can measure both the inside and outside diameters of the ring.
The art of chain mail involves linking jump rings together in a specific way to create a particular link or pattern. There are dozens of chain mail links to discover and in most patterns you'll put multiple rings into one. So, for chain mail artists, the inside diameter is important to know. It helps you figure out how many jump rings will fit inside another one.
Most shops offer jump rings with the gauge and outside diameter labeled,
or with no measurements listed at all (which is maddening!). However, many chain mail books and project instructions list the gauge and inside diameter of the ring.
What happens when you want to do a project that lists the inside diameter of the needed ring, but your local bead shop lists only the outside diameter? We just have to do a little math! But before we get out our calculators, let's talk for a second about gauge.
As I said, gauge describes the width of the wire. Just to make things complicated, there are two different wire gauge charts. America and Canada use the American Wire Gauge (AWG) standard, also called B&S. Most other countries use the Standard Wire Gauge (SWG) standard. (However, some industries use AWG worldwide). I am using the AWG standard here.
The chart below will give you a basis for calculating your jump ring measurements:
Now for the math. If you only know the outside diameter (OD) of your ring, subtract twice the width of the wire gauge from the OD to get the inside diameter (ID). Reverse this calculation to find the OD when you only know the ID.
OD – (2 x gauge) = ID
and conversely,
ID + (2 x gauge) = OD
Let's try an example. I have a bunch of 6mm (OD) 18ga jump rings. My chain mail book calls for jump rings based on the inside diameter. I want to know which project I can use my jump rings for so I will use the first formula.
OD - (2 x gauge) = ID
6 - (2 x 1.024) = ID
5 - 2.048= 2.952mm
(Result: I can use these with projects asking for 3mm (ID) 18ga rings)
Similarly, here is a converse example. Let's say my project calls for 3.5mm (ID) 20ga rings, but I shop at a store where they sell by the outside diameter. Therefore, I will use the second formula to find the OD so I can know what to buy at my shop:
ID + (2 x gauge) = OD
3.5 + (2 x 0.812) = ID
3.5 + 1.624 = 5.124
(Result: 5mm (OD) 20ga should work fine for this project)
A little jewelry math is a small price to pay for eliminating the confusion over jump ring sizes! Have fun linking!
Up close look at one link of Byzantine Chain Mail