Sew out an 18 millimeter capital "I" character or use the sew test disk that is supplied with your machine. For accuracy, sew out the test on samples of the material that you will be embroidering. The sew test will also help determine whether there is a bobbin tensioning problem versus a top tensioning problem. If the bobbin thread is consistently too wide or too narrow on all the needles, there is a bobbin tension problem. See figure1.
The top row of this sample shows proper well-balanced tension with the 2/3 top and 1/3 bobbin thread on all needles.
The middle row shows a problem with the bobbin thread tension because it is consistently too wide from needle to needle.
The bottom row shows a problem with the top thread tension on a couple of needles. The bobbin thread is inconsistent from needle to needle indicating that any adjustments should be made to the upper tensioners.
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