Before I started sewing my jeans together, the MPB Jeans Sew-Along suggested to test needles, thread and fabric first. Especially since I am using some heavy fabric, and heavy topstitching thread.
Before I began test stitching, I consulted my sewing library for advice. Both the Reader’s Digest Guide to Sewing and DK’s The Sewing Book were silent on the matter of thread tension. I did find some help on adjusting tension in Nancy Zieman’s Sewing A to Z, and in my sewing machine’s instruction manual. So if you need to learn more about thread tension, your machine’s instruction manual would be a great place to start.
Sometimes when checking tension for sewing machine and serger stitches, I find it useful to have a magnifying glass on hand to get a closer look at the stitching. You can see how the top and bobbin threads wrap around each other, as well as how much the bobbin thread shows on the top side, and vice-versa.
For both seaming and topstitching on the jeans project, I am using a #100 denim needle. It’s strong enough to get through the fabric, and the eyelet is large enough to accommodate the heavy topstitching thread.
I am using #80 weight jeans topstitching thread from WAWAK Sewing and Tailoring Supplies (their house brand). I purchased five spools in different colors – red, olive green, navy blue, black, and for this project, “Levi Gold.”
The top tension dial on my machine is numbered from 0 (loose) through 9 (tight). The nominal setting is supposed to be 4. I did a series of test stitches starting at 4, and going up by one number each time. The MPB Sew-Along suggested that a higher top tension would be necessary, to help pull the bobbin thread up through the heavy fabric. Also, the heavy thread will naturally increase the bobbin thread tension. (I didn’t try adjusting the bobbin thread tension, because it’s a teeny tiny screw with no markings and I’m afraid I will screw it up.)
I started with “normal” setting of 4, each row of stitching bumping one number higher.
Comparing the top thread and the bobbin thread, we see there are some pretty massive differences at the lower tension settings. At 4, the top stitch looks okay, but the bobbin side has all kinds of loose, unsightly loops. As the top tension goes up, the bobbin stitches look tighter and tighter, until at about 8 they more or less match the top stitching. I suspect the best setting is the highest one that gets the stitches on both sides to match, without being so tight the top stitches suffer or the fabric starts puckering. So 8 is the setting I’ll be going with when working with the topstitching thread.
Regular Thread testing
I also use the #100 denim needle for regular seaming. I’m using Gutermann all-purpose thread, in navy blue to match the denim. (For the test, I used white to contrast the denim).
Again, I started out with the “normal” setting of 4, and sewed each row one tension number higher.
Here, the bottom and top stitches match each other best with the tension set to 6. Above that, the top stitches start to suffer – the tension is so high, they pull up all the bobbin thread, lose their shape, and look like a flat line. So I will use 6 with the regular thread.
I haven’t experimented much with more “regular” needle and fabric combinations, say an 80 needle with all-purpose thread on some cotton shirting. But I do suspect the tension settings on my machine might be slightly out of adjustment, for instance a setting closer to “5” behaves a like “4” should. So if you’re following along, and especially if you have the same machine I do, you should do your own set of test stitches to determine the best tension setting for your project.