Are you using an industrial machine ? Is the upper thread tension too tight? I sew with a #46 weight nylon thread all the time. I also have a 69 weight, but it is much heavier, I don't use it much. The needle needs to be turned the right way, and make sure your tension isn't too tight. For tarps, use a minimum 14 sharp needle. A 16-18 would be better. Usually I have a little trouble with this thread if there is a burr on the needle. Don't sew over any pins.That will mess up your needles, and stitch timing real fast. You can use a stapler inside your seam allowances, turned longways, and out of the way of the feet and needle. This is better than pins on big, heavy stuff. I hope this helps. K
Nope, I'm using my Rocketeer, not an industrial. I keep loosening the thread tension, the stitch is coming out fine tension-wise but it seemed kind of tight at first when needing to pull some extra thread out - so now it's at like a 5 which is really low for that machine! The nylon tarp is 200 denier, so it's really not very heavy at all - I started out with a 14 sharp but switched to a 16 sharp, I don't think I have any 18s right now. And it's a new needle, so I don't think there's a burr on it. The thread is Gutermann "Bulky Nylon" textured overlocking thread, No. 120. See, they'll be dying the tarps after I get done sewing them, and they want nylon thread so it all dyes the same...but I got some other nylon thread to try and it's all loosely twisted like the Gutermann thread is. I suggested using polyester thread and she's afraid it'll shrink. Any other thoughts?