Embroidery machine tensions can make or break a project. How, exactly, do they work?
When I had my very first sewing machine and was first learning to sew as a young girl, you didn’t dare touch the tension for fear of messing up your machine. In fact, I remember vividly the man teaching our introduction class to our new machines to "never, every touch those tensions!" We really did not have many choices when it came to threads. We were not doing embroidery at the time and we didn't have computerized machines so there might have been a little bit of merit to the practice.
I wish my machine technician would have just taken 5 or 10 minutes to sit down and explain to me how tensions work so that when I ran into an issue, I might be able to fix it on my own instead of having to bring the machine to him every single time I had a tension issue.
That is not to say all tension issues are minor. This tension series is not going to replace a good technician but it might save you a trip or two.
How Does Tension Work on a Machine?
This information is geared toward embroidery machines because that's obviously what I deal with more often but a lot of this will apply to sewing as well.
Tension is kind of like a tug of war game. Your upper tension on one side of the rope, and your bottom tension on the other side. Whichever is the strongest will win and the thread will go that direction. If your bottom tension is the strongest contender, the thread is going to pull down toward the bobbin. If the upper tension is the stronger of the two, the thread is going to pull up toward the top.
The upper thread runs through two tension disks. They are two little silver discs that either separate (widen) or go together (narrow) to adjust tension on the thread. When you raise the presser foot, it opens the tension discs so that the thread just falls through and can easily be pulled from the needle.
Lowering the presser foot engages the upper tension discs (makes them go together) so thread pulls against your bobbin thread. The same thing is going on with the tensions in your bobbin case. Thread goes through a little slit between two pieces of metal. The ease with which bobbin thread moves through the slit depends upon how tight the bobbin screw is adjusted.
For regular sewing, as you well know, we use the same thread for the top as we do for the bottom so there is no difference in the strength or the thickness of the threads. Manufacturers set up machines so that they sew at a balanced tension which means stitching is going to look the same top and bottom, no matter which side you see.
With embroidery, we typically use a 40 weight thread on top and a much finer thread on the bottom (60 to 90 weight). Because bobbin thread is thinner than top embroidery thread, it passes through that little tensioning space much more freely, which means less resistance and less pull, so that the upper tension is going to win. The upper tension will pull bobbin thread to the top and you are likely to see it.
Check back to find out how to test and how to adjust your tension. See the full video here.