Thread Tension Conundrum

[Johnny5]

Pulling my hair out, hoping some industrial machine veterans can help. I am struggling to get consistent thread tension on my Consew 206RB. I am working in upholstery vinyl (Naugahyde) and will test the tension using the same vinyl I am am using for my project and doubling it up. I dial in the tension until it is perfectly even on both sides on my test strip. Inevitably when my project is done and I turn it over, the bottom tension has become greater than the top and thread is pulling through, never the other way around. I've tried adjusting the bobbin case tension but that doesn't seem to make a difference. I've tried different needle sizes (currently using a size 18 needle with #92 thread) with no difference. Wondering if my bobbing winder is the problem? It struggles to make even bobbins regardless of the tweaks to the disk tension and angles of the thread. Unsure what adjustments to make, any suggestions would be much appreciated.

[Gump]

I have the same machine and use a 20 or 21 size round point needle in vinyl with 92 thread. Bobbin tension should be just enough to pull thread straight as you pull it out of the machine. Once set, forget about your bobbin tension and just use your top adjustments. I can sew 2 layers of vinyl or 2 layers of 8oz vegtan with the same settings. Needle and thread charts are made for sewiong fabric. Most times vinyl and leather will require going up 1 needle size from recomendations due to grab of the vinyl.

[Johnny5]

38 minutes ago, Gump said:

I have the same machine and use a 20 or 21 size round point needle in vinyl with 92 thread. Bobbin tension should be just enough to pull thread straight as you pull it out of the machine. Once set, forget about your bobbin tension and just use your top adjustments. I can sew 2 layers of vinyl or 2 layers of 8oz vegtan with the same settings. Needle and thread charts are made for sewiong fabric. Most times vinyl and leather will require going up 1 needle size from recomendations due to grab of the vinyl.

Thanks @Gump I have tried a size 20 needle as well with the same results, but I am using sharp point needles. Will the round points help?

[Gump]

Round points are also known as sharps. My machine was acting up a couple of years ago, and I had dirt build up under the bobbin case tension spring. Cleaning helped for a while and then I just changed out the bobbin case. I bought my machine used and it came with two new bobbin cases so I guess that is a wear item to be changed regularly as needed. No visible trouble with bobbin case, but a change solved my problems.

[kgg]

17 hours ago, Johnny5 said:

Inevitably when my project is done and I turn it over, the bottom tension has become greater than the top and thread is pulling through, never the other way around. I've tried adjusting the bobbin case tension but that doesn't seem to make a difference.

Some machines can be very particular in the way you install the bobbin so it unwinds counter clockwise or vise versa. I would suggest installing the bobbin in the bobbin case the opposite way and see what happens.

17 hours ago, Johnny5 said:

Wondering if my bobbing winder is the problem? It struggles to make even bobbins regardless of the tweaks to the disk tension and angles of the thread. 

This maybe as simple as the bobbins are not to spec as in too small, center hole to big, not balanced, out of round. I would suggest replacing with a Juki spec bobbin.

A couple of photo's of the threading path from the spool of thread to the needle maybe also helpful.

kgg

[Johnny5]

5 hours ago, kgg said:

Some machines can be very particular in the way you install the bobbin so it unwinds counter clockwise or vise versa. I would suggest installing the bobbin in the bobbin case the opposite way and see what happens.

This maybe as simple as the bobbins are not to spec as in too small, center hole to big, not balanced, out of round. I would suggest replacing with a Juki spec bobbin.

A couple of photo's of the threading path from the spool of thread to the needle maybe also helpful.

kgg

Thanks @kggI will try getting some new bobbins and see if that helps, the ones I am using came with the machine when i bought it. The bobbin case is for sure loaded correctly loaded. I did replace it with a new one and also replaced the tension assembly when I got the machine less than a year ago (This machine is over 40 years old).