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[TedP]

Greetings,

I have been thinking that my bobbin thread tension is too loose, but the tension adjustment is max'ed out on the bobbin. Since I have been using a sew foam backing it has not been a huge problem as that compensates a bit. However, when I am sewing plain vinyl-to-vinyl the seam feels a bit loose and applying some tension on the vinyl panels (pulling them apart) will show the thread more than it should.

Then, it occurred to me that I am using 'slippery' thread (PTFE - Tenara to be exact) and the lack of friction of the thread itself may be causing the bobbin tension to be less than it normally would be with a different type of thread. The top thread, obviously having more spring-loaded tensioning can certainly go tighter, but then it pulls the interlocks to the top of the vinyl.

Any thoughts, ideas, experiences dealing with the PTFE threads and getting more bobbin tension? Are there different bobbins to achieve such? Machine is a Consew 206RB-4.

[MalcolmM]

Clean your bobbin case and spring with solvent, any lubricant from the machine head will over lube the bobbin.

[TedP]

Yes, thank you. I did clean the bobbin as part of trying to remedy the tension, but the thread still seems to have minimal tension. I have not experimented with a nylon or poly thread yet for comparison. Just wondering about the 'teflon' thread (Tenara). It is fairly slippery and when I hold the threads at the start of a seam, it easily slips through my fingers.

[Adam12]

Do the drop test for your bobbin tension and do the rest of your adjusting on top. When changing thread size, type or even color; i will crank the top tension down until the knot shows on top. Then very slowly decreasing top tension as i sew a few stitches at a time until the knot disappears. If your knot is pulling to the top too easily, try a smaller needle. If the needle hole is too big, the take up lever overpowers the bobbin tension pulling to the top. Should help with the thread showing when pulled apart

[TedP]

Thanks, I'll do some more testing & adjusting as you recommended. I am using regular Tenara thread (92) and a 110/18 needle. Not sure I can go down much on needle size with the thread, but a smaller needle makes sense.

I have used the 110 needles with the 138 Tenara, but that seemed a bit tight and the needle would occasionally 'bunch' the thread.

I suppose the thinner the material you are sewing makes a difference, as there is not much 'play' as to where the knot in the stitch resides within the layers of fabric. Probably +/- 0.5 mm for typical vinyl fabric. Using sew foam gives the stitching more play.

I'm more particular about thread tension when just sewing through 2 layers of vinyl or canvas. . . But I guess too much tension may cause the fabric to bunch up.

I've also ordered a few bobbin cases as the one I have is what came with the machine (used) and not sure how old, etc.

[Adam12]

18 needle sounds right for that thread, agree not sure you can go much smaller but a size smaller is worth trying if you don't get it just right with tension alone.

[TedP]

I've also seen some thread tension testing devices, and wonder if anyone has found those useful?

[MalcolmM]

To use a thread tensioning scale you have to know what your machine is rated for. I use a Lyman trigger scale for my embroidery machine, I already owned it and didn't want to spend the money for a proper bobbin case device and a top thread scale which are different designs. I remember seeing a 35 gram rating on my Consew P1206RB so that's what I tested my bobbin for and then adjust the top by testing in fabric.