You may have gotten your new machine and been confused about the white disks that came in the accessory bag, or maybe you knew that they go on with the thread but you don’t know why. Spool caps are a great tool for your sewing machine. Contrary to popular belief you don’t always need one! Most of the time spool caps are used to keep the thread from falling off of your machine while you are sewing, but they have a more important use. Some spools will have ridges on the edge of the plastic, or small splits that hold the thread when storing it, and the spool cap extends past that edge to prevent the thread from getting stuck and causing tension issues. See the image below for the ridges.
So how do you use a spool cap?
When putting on a spool cap, the flat side will go against the spool while the pointed edge goes away from the spool (not all machines will have a pointed side). The cap should rest against the spool but not shove, and there should be no gap between the two. If the cap is put on too tight the thread may get stuck on itself and the cap would prevent the spool from spinning to release itself.If there is a gap between the two threads can get wrapped in between them.
Spool caps come in various sizes and it is recommended to match your spool size as close as possible. If you are using a skinny spool you will want to use the small spool cap rather than the large one. If you are using a large spool, you will want to use the large spool cap. If your only issue was the spool falling off, and not the thread catching, you could use a small spool cap on a large cone, but I recommend staying consistent and matching sizes to make it easier and more consistent.
Some spools, such as Aurifil thread or thread cones, do not necessarily require a spool cap. These spools have more mass at the end which helps to keep them from wiggling off your machine (though they can still fall off in embroidery due to the high-speed vibrations). They also have no rim on the front of the spool, so there is nothing for the thread to catch or get stuck on! If you find that these spools are still falling off, I would recommend using a spool insert. If you don’t have one, you can use the smallest cap that your machine came with. Using too large of a spool cap would create a gap for the thread to get stuck in since there is no rim but rather the spool extends out beyond the thread.
Have questions? Feel free to ask them in the comments!
Happy sewing!
