When it came time to buy thread for quilting, I decided to order 100% cotton 50 weight Aurifil thread. Almost all of my quilting books had recommended 100% cotton 50 wt, and I didn’t question their advice. And the particular shop I was ordering from, only sold Aurifil thread. As I began to wander into the quilting forums and blogs though, I realized that this wasn’t a universal rule that everyone was following. So I’ve decided to revisit why 50 weight 100% cotton thread is often recommended for quilting, and why some might use different types of threads. And, if there are any special considerations when picking thread for the 15-91.
Thread Material
100% cotton thread seems to be highly suggested in quilting due to the following:
It is soft
It has a matte finish (so it blends in better)
It does not stretch
It can withstand heat (from pressing with an iron)
It is more consistent if you use same type of thread as quilting material (which is typically cotton). Consistency is important because for example, if you wash your quilts, different materials could shrink differently
But that doesn’t mean there isn’t room to use other types of thread. For example, if you are using a quilting material that isn’t cotton, it probably makes more sense to use a thread that matches that material. If you are trying to go for a very thin thread but still want it to be strong, it might make more sense to use polyester (although there is the potential that over time, the polyester thread would cut through cotton material).
Now, while I originally wasn’t going to talk about “high quality” cotton thread, I think it would be hard to close this section out without mentioning it. In the eyes of the quilting community, quality of your cotton thread does matter. It matters because “high quality” thread
Is more tightly wound and smooth which means it isn’t as lint prone (thus your machine is less likely to get clogged up), and your seams will lie flatter and be prettier
Is stronger and less prone to breakage
So if you have the money and are planning to use cotton thread, you should try to buy “high quality” cotton thread. It is kinder to your machine, will contribute to a quilt that lasts longer, and will give a nicer effect to your quilting work. Some of the brand names that you will see thrown around when “high quality” cotton thread is mentioned are: Aurifil, Gütermann, and Mettler. There are probably more but those are the most common ones I have seen.
Thread Weight
When I first starting researching about thread weight, I thought this would be a very simple topic. IT IS NOT. I’m beginning to understand why the quilting books just told me what to buy rather than try to explain thread weight. Part of the problem is that thread weight terminology is specific to cotton thread (which is often used in quilting), and this is a more US centric concept (for historical…. reasons). It is known alternatively as cotton count, and internationally not everyone follows this system. Sewing life goes into some detail about this, but essentially what you need to know is that while thread weight corresponds with thread size, it isn’t the same thing. Thread weight in this instance is referring to the length of thread you get from one pound of cotton. The general rule of thumb is that the lower the thread length (i.e. thread wt.), the heavier the thread (and likely the thicker the thread). Adding in some additional complexity is that when shopping for cotton thread you could see 50/2 vs 50/3 thread. These are not the same threads. One is a 2-ply thread, and the other is a 3-ply thread. The 3-ply thread is thicker. If you see 50 wt. on its own, it could be 2-ply or 3-ply. Confused? I certainly am. Looking back at what I bought for quilting, the website doesn’t even list whether its 2-ply or 3-ply. I had to look at the threads themselves and my larger spools are marked as 50/2 while my smaller spools are just marked 50.
Quick Note: While I don’t want to add to the confusion, I do want to quickly mention TEX / V classifications for thread weight since it comes up below on considerations for the 15-91. I would recommend checking out Superior Threads and Sailrite, but the short summary is that TEX is an alternative standard meant to create consistency internationally on thread weight (the higher the number goes, the heavier the thread). V classification is typically used in the US commercially for twisted, multi-ply bonded nylon and polyester thread. And apparently quilters are ruining it for everyone because they love the weight standard? Anyway… I tried to find a chart for you all that directly compared TEX and cotton count thread classifications but this is the best I could come up with.
But let us get back to why 50 wt. in particular is often recommended for quilting. 50 wt. thread seems to get recommended a lot simply due to the fact that its a good middle ground between having too thick of a thread vs too thin of a thread when sewing your quilt layers together. Also 50 wt. thread can be used across the entire quilting process. This gets brought up because you can actually use a smaller thread when you are piecing (i.e. as small as 80 wt.) if you want to try to get flatter seams on your quilt top. But 50 weight is still small enough that you can piece with it if you want to, and that saves you from having to switch out your thread or buying different thread weights.
Why would someone use heavier/lighter thread than 50 wt.? When I revisit my quilting books and read them a bit closer, some of them do touch on this topic. For example, 40 wt. is often cited as a good thread to use not only if you want your thread to stand out a bit, but also if the quilt will get heavy use. If you are going for a “soft” effect, or you want your thread to disappear more into the fabric, you might chose a 60 wt. thread.
Does it matter if it is 2-ply or 3-ply? Research suggests that there is not a straight forward answer to this question. If you are buying high quality thread though, it seems like 2 ply is sufficient due to the strength of the thread. If you want your thread to stand out more, you can use a 3-ply thread.
Thread Considerations for the 15-91
When it comes to the 15-91, they are pretty tough machines. As long as they are in good working order, you should be able to use it with a wide variety of thread. You will only begin to hit the limitations of the 15-91 at TEX 90 / V92 thread. Your machine can technically do it, but it is not recommended to go above TEX 70 / V69 thread.
Credit also must be give to Suzy Quilts because they mentioned something I hadn’t even thought about, which is that some threads are labeled as quilting threads but are actually meant for hand quilting. The thread has a special coating and you don’t want to use that thread in your machine. While I haven’t seen discussion in the vintage community specifically on this topic, I’m guessing its a pretty safe bet that if it sticks to the metal parts of a modern machine, that it is also bad news for the 15-91.
The only other consideration for the 15-91 I could come across, is that you might need to adjust the tension in your lower bobbin holder and/or in your top thread tension depending on the weight of your thread. Larger thread might also mean you need to get a larger needle.
Felt pads for thread spools
2022-01-24 Update: As someone who uses Aurifil thread on the 15-91, I though I should mention that sometimes you may encounter cross wound threads like Aurifil (as opposed to stacked threads where all the thread is spun parallel to the spool). You can identify a cross wound thread by the zig zag pattern in the wound thread. This thread is the best used when fed from the top of the spool (i.e. a horizontal spool holder) rather than the side of the spool. You can ran into tension issues otherwise. All that being said, I haven’t had issues using Aurifil on the 15-91 (which has a vertical spool holder). The only thing I’ve added to my machine is a felt pad below my thread spool to reduce friction. If you are having tension issues using cross wound threads on a 15-91 or you would just prefer to have a horizontal spool holder, it is possible to find a horizontal spool holders to attach to you machine.
Also if you need felt pads and live in Canada…. I have a surplus.