Tensioning on the fly...

[Ripper70]

Hello All,

I have a few items that I've been trying to stitch on my Cobra Class 26 that have been proving to be a challenge. When a single item has several different layers resulting in varying thicknesses and requires a single, uninterrupted stitch line, how do you accurately adjust the tensioning on the machine to accommodate the differences?

Is there a best practice for making these adjustments? Turing the tension knob seems like a hit or miss proposition and without any gauge or markings on the dial it seems like pure guesswork to correctly tension the machine on the fly. How do you all overcome this issue?

Thanks in advance for any assistance.

Ripper70

[LiftPig]

I can tell you what I do - it might not be the According to Hoyle right thing but it works for me.  I set my tension for the thinnest part.  Now I know the knot is somewhere in that thin material.  Theoretically, going up in thickness should leave the knot in the same general place, and while it may not be right in the middle of the layers, it's buried.  You could also give the tension knob a couple clicks tighter when you go up in thickness, keeping track of how many times you do that, and then go back down if the material gets thin again.  

When my machine is sewing well this works - I might get one wonky knot that just shows right at the transition between thicknesses but I can poke that down with a blunted awl.

[Ripper70]

Still struggling with tension issues. Never mind the "tensioning-on-the-fly" between varying material thicknesses. I'm just trying to get a proper straight run here. At this point I've set the bobbin tension to a minimum and am trying to only use the top tension with micro adjustments to set the thread properly. In the sample pic below I'm sewing a 3-4 oz. veg tan to a heavy (1mm thick) upholstery using a #19 needle and #92 thread. The top example shows top tension too tight. A small loosening adjustment resulted in the bottom run showing some improvement but some stitches that are still pulling up. Even with these micro adjustments I just can't seem to get an acceptable and consistent balance between top and bottom tension. What would your best recommendations be moving forward from here. 

[MtlBiker]

@Ripper70 - Have you tried a #20 needle?  From my experience that's a better choice for v92 thread, especially on many materials.

[Ripper70]

Okay. Taking MtlBiker's advice, I switched out to a #20 needle using the same #92 thread and making no changes to my last tension settings. Pics below show the result. The top photo shows the top side (leather), which at first blush, seems better and more consistent. The bottom photo shows the back side (upholstery) which shows bobbin tension just a tad too tight. The second row of stitches shows the front and backside result after tightening the top tension just one click. Any suggestions as to which of the other tensioning options available on the Class 26 would allow me to split the difference here or is it just not possible to dial it in with that kind of accuracy?  

Edited June 16, 2023 by Ripper70

[TomE]

Rethread your machine making certain that it's threaded correctly.  The thread path on a Class 26 has a couple of subtleties, there's no written instructions (?), and I watched several different instructional videos before I realized my mistake.  That said, it's a handy little machine that does a great job running through all sorts of materials and thicknesses.