Cobra Class 4S Tension Issues

[bylinesupplyco]

So I recently have been having some tension issues with my Cobra 4.

I was using 207 thread with a size 25 needle, and even after messing with the bobbin and top tension, the knot was still coming through. Called Steve and he said the needle was too big. Recommended size 23 needles. Installed a size 23 needle, and the issue is still arising.

Anyone know how to fix this?

Attached some pictures for reference. some spots are fine, other spots the tension is off.

[TinkerTailor]

What kind of glue are you using and how long have you let it cure? Partially dried glue or areas with heavier glue can cause greater drag on the thread leading to inconsistent stitching.

What is the total weight of leather you are sewing? Is it even thick enough to hide the knot on 207? If that is 2 layers of 3-4oz, it could be only 6 oz total thickness which is pretty thin for that machine. I have some harder temper 3-4oz veg that is very difficult/impossible to bury the stitch in with 207, while i have some oiltan in the same weight that will hide the knot at almost any thread tension.

In the second pic, nearly every knot is in the same place and visible on the top, a little less top tension may solve this.

[bylinesupplyco]

I've been using barge cement, and letting it dry for about 30-45 minutes.

As for the leather, I only use 3-4 oz. veg tan, and English bridle. Wallets mostly is what I make.

If I were to use 138 thread, what size needle would I use for that?

As far as the top tension goes, I have the nut almost all the way unscrewed. Anything more and the nut would be close to falling off.

[TinkerTailor]

I've been using barge cement, and letting it dry for about 30-45 minutes.

As for the leather, I only use 3-4 oz. veg tan, and English bridle. Wallets mostly is what I make.

If I were to use 138 thread, what size needle would I use for that?

As far as the top tension goes, I have the nut almost all the way unscrewed. Anything more and the nut would be close to falling off.

Top tension nut....not nuts? Your machine should have 2 thread tensions on the top thread, one on the back at the top and one halfway down the face of your head. They both need to be adjusted and balanced with each other. Just changing one will make things all wonky, or not change much at all.

I have not run 138 through my 441, however here is a chart of standard needle and thread sizes for your machine.

Not that 207 is wrong for your application, it is just harder to hide the knot with fatter threads and some types of thinner leather. I sew thin stuff with 207 all the time. I made a leather flatcap out of super soft 3 oz deerskin and it stitched fine.

I will say that it took me a while of tinkering to get my machine to work the way i want, and don't plan on messing with it much unless i have too. @07 works for most of what i do so that is fine.

I would try to let the glue dry overnight and see if that makes a difference.