I got my Cobra 4 a few weeks ago, I've been trying to learn to use it. I've watched several videos on it from Al Bane and the like. One thing I'm struggling with is getting clean backstitches. I usually start with the needle a stitch lengths past where I want the stitching to start and stitch backwards for three stitches, then switch the machine to forward and go the end of my stitch and then reverse for three stitches. Sometimes the backstitched area comes out clean and i can see the forward and backward stitches and they're clean and parallel. About half the time I end up with weird knots and seemingly extra threads tied in there somewhere. I'm not sure what I'm doing wrong. Is this a common mistake? Here are some pictures to show what I'm talking about it. I'm currently using size 207 thread and a size 24 needle, though I felt like I was experiencing the same problem using the 277 thread and size 25 needle that came on the machine.
EDIT: This is just two layers of ~6oz veg tan I got from Tandy a few years back, it isn't the best leather, a simple pocket knife slip. I'll probably be mostly doing 3 layers of 6-7oz+ for fixed blade sheaths. I've since bought some Hermann Oak to try out, but I'm currently just practicing on the less expensive stuff I got from Tandy. Maybe this is a thread tension issue? I haven't made any adjustments on the machine, is this an issue of the knot not being centered in the layers of material that are much thinner than the 1" thick samples that came with the machine? Should I expect to change the tension between something like a two-layer pocket knife slip and a three-layer sheath (including the welt)?
BAD
BAD
Not bad...