Problem With Tension

[8thsinner]

I just picked up a jones model 574, looks something like below but I think my question is generalised.

With two layers of sofa leather hair to hair side it stitches no problem, for two layers flesh to flesh the bottom side when finished feels rough and the loops are sticking out.

Obviously a bobbin issue, and everything is tightened out, I tried adjusting both variably but can't get a good result.

Picture

Is there normally a way inside the machine to reset tension strength or something?

I know nearly nothing about fiddling with sewing machines...

Edited September 1, 2011 by 8thsinner

[wolfe9]

You might get better answers if you post pics of the stitches that you are having problems with , otherwise people are just guessing ..

Good luck

[8thsinner]

It's just a straight stitch and looks like the lower right image...

http://www.threadsma...-tension-03.jpg

Edited September 2, 2011 by 8thsinner

[dbusarow]

The picture shows not enough top thread tension. I guess it could be WAY to much bobbin tension but based on my Cobra's bobbin tension vs its top tension the bobbin can't get that tight unless somethings broken. You need to tighten up the top. My top tension is typically set so that I have to release the top tensioner to remove the item being sewed from under the foot. I'd break the needle before I pulled any thread loose without doing that.

Dan

[8thsinner]

I checked through every thing from scratch again, the top thread wasn't actually between the tensioning disks properly, thats why it wasn't adjusting when I changed it.

Problem solved.

Yay. Project now finished.

[wolfe9]

Good to hear ..

[RFMarsh]

The picture shows not enough top thread tension. I guess it could be WAY to much bobbin tension but based on my Cobra's bobbin tension vs its top tension the bobbin can't get that tight unless somethings broken. You need to tighten up the top. My top tension is typically set so that I have to release the top tensioner to remove the item being sewed from under the foot. I'd break the needle before I pulled any thread loose without doing that.

Dan

I just got my Cobra Class 4 and am struggling to figure out the tensioning combinations. I have played around enough to get a good looking stitch on a single layer of 8/9 oz. but then, when I change anything (e.g. going to two layers, switching to a firmer leather of the same thickness), the stitch is horrible. Is there a tutorial on setting stitch tension on the CC4 somewhere?

[dbusarow]

No tutorial that I know of.

If it's any consolation it took me quite a while to get the tension figured out too. I just thought I was stupid...

Pick what you sew the most, e.g. 2 layers of 8/9 veg tan. Work the tension out on those. Steve mentions in his English manual that you need both the top tensioner and the one on the side to be syncronized. I forget the phrase he uses but something about always adjusting both at the same time.

Once you get them both in the ball park, and it was just a lot of trial and error for me, stick to that sentence. Adjust them both at the same time. I find that the lower one on the side takes smaller adjustments but if you are tightening, tighten both. If you are loosening, loosen both.

You'll eventually get it and once you do even making huge changes in the leather (going to say 3 layers of 16 oz from your 2 layers of 8 oz) only require a little bit of adjusting.

To give you a ballpark to start in, mine are showing about 6 threads of the top adjuster's bolt and about 2 threads on the one on the side.

Good luck!

Dan

[dirtclod]

I don't have a Cobra but the same style machine i was told to sew on a couple pieces of chap leather till the stitches looked right and they would work fine for just about every other thickness. So far that has worked. Good luck.

[leatherkind]

I had so mach fun trying to figure out correct tension...

It seems to be more difficult to adjust with thin soft leather then with thick and stiff.

For example i was stitching the zippers to soft leather and you can tell that the leather side looks shrunk compare to the zipper.

I guess the tension was too high.

Unfortunately I could not find anywhere numerical specifications on what the tension should be. At best it is "a little more" or "too much" so i had to guess.

Maybe i just did not look in the right place? Please let me know if you have it.

I also realize that if you try to make a complete chart that is probably going to be enormous.

Just imagine now many different tension mechanisms are out there, how many different threads and coatings, and how many different materials...

Nevertheless, one problem at a time.

Here is my example of thread tension. I would greatly appreciate if you tell me if I have it correct or not.

I measured the thread tension by pulling the thread to the back of Cowboy 4500 with luggage scale.

The leather is 1,2 , and 3 layers of 2mm (3/32") oil tan which is not very soft. All together they are about 1/4".

In all three stitch samples the top thread is at constant tension of 1800g (4lb).

The bottom tension is changing three times 200g (7oz), 850g(1lb 14oz), and 2kg (4lb 8oz).

Thread is bonded Nylon #346 (about 1mm in diameter) made by Linhanyl and the needle is #25 leather point.

I have circled obviously bad spots with red (horror) and yellow (outrageous).

As you can see there is little difference for thick material but not so for thin.

I would like to mention that to change the bottom tension so much i had to turn the bolt only 1/2 of a turn.