In this video, we introduce one of the most important adjustments you’ll make on your embroidery machine: adjusting thread tensions. When you first receive your machine, both the upper and bobbin tensions are already preset for you. To verify and fine-tune these settings, we run several different types of tests, including the H test, I test, O test, and FOX test.
Each test helps us check tension by sewing sample embroidery and examining the back of a satin stitch. Since most lettering is made up of satin stitches, these tests are ideal. When inspecting the back, we look for a balance: approximately one-third top thread, one-third bobbin thread, and another one-third top thread in fairly straight, even columns.
If we see too much white (bobbin thread), it usually means the bobbin tension is too loose or the top tension is too tight. If we see only a narrow strip of white, the bobbin tension may be too tight or the top tension too loose. To properly diagnose the issue, we review the majority of threads. If most threads look good and only a few are off, it's likely a top tension problem. If most are off, the bobbin tension is likely the cause.
The H and I tests provide a quick overview of the machine’s tension, while the FOX test offers a more precise evaluation. The FOX test is more demanding because it includes sewing in multiple directions: horizontally and vertically for the F, circular motion for the O, and diagonal stitching for the X. This range of motion puts the machine through a more thorough tension test. We’ll now walk through an example of an I test to show you what to look for.
Looking to perfect your machine's tension? Check out our tension gauge tool.