Now you see my knots now you don't on my Cobra 4

[veritasleather]

Hey guys!

Im a noob here, first post. I recently acquired a Cobra 4 from the leather machine co. picked up from Dave about a month ago. Now my problem is that when I sew my knots pop up on top for about 4-5 stitches then they disappear for another 4-5 then they reappear. Please understand I am just learning how to drive this thing. Never used one before. is it me pushing or pulling the leather? or is this a tension problem? thank you guys!

Frank

[Wizcrafts]

It is either caused by an out of round or badly wound bobbin, or twisty/excessively bonded top thread, or rawhide in portions of the leather.

[OLDNSLOW]

Wiz, would you mind extrapolating on that just a bit more.  If winding the bobbin on the machine how can it be done incorrectly, assuming the bobbins being new is there a way to ensure they are all good, and what to look for in the thread.

thanks

O n S

Ron

[Wizcrafts]

If while winding a bobbin you have the little movable thread aiming guide misaligned on the left-top of the machine, the windings will build up on one side or the other (it should be adjusted to feed evenly across the bobbin, with good thread tension). Or, the bobbin loading thread may be jumping in and out of the bobbin winder's tension disks on top of the machine. A bobbin loaded thusly is unbalanced and may wobble as it feeds the thread through the tension spring. Or, if the owner leaves too much length on the starting thread stub, it may catch intermittently on the ejector/anti-backlash spring inside the bobbin case. This will cause the bobbin to feed in a jerky fashion, rather than smoothly. Finally, the bobbin itself may have been formed less than perfectly aligned on the disk ends. Or, the length of the bobbin may be under or over optimum length. I have accumulated 441 bobbins that have different lengths from end to end. The oversize bobbins tend to bind a bit in the shuttle and add unwanted tension to the bobbin thread, compared to a slightly shorter bobbin.

[OLDNSLOW]

Thanks for your input, so I guess it wouldn't hurt to put a caliper on a few bobbins to see if they are within spec.

[LumpenDoodle2]

Wiz is spot on as usual, especially regarding the quality of the bobbin.   You would be surprised how 'out of true' a new bobbin can be, and it will affect you machines stitch performance.   That, and winding you bobbins too loosely.

[veritasleather]

Thank you Wizcrafts, I am still using the bobbin that was loaded with the machine when I picked it up from the leather machine co. I think I will attempt to wind a bobbin myself per your comments. I hope this fixes things, again, am still learning. Trying to follow what all the leather machine co. videos suggest. The long leads of thread before starting to stitch also makes sense. I do notice the knots up first at the beginning of stitching then they might go back down for a couple of more stitches. Thanks guys!

[Darren Brosowski]

Could also be as simple as the thread not coming off the top spool evenly

 

[veritasleather]

 

Could also be as simple as the thread not coming off the top spool evenly

 

Thanks Darren, so what you mean is that it could also be that there is a problem with the top spool itself? Or tension is causing the un even feed?

[MADMAX22]

I believe he is talking about the spool of thread. If it doesn't come off smoothly it will mess with your top tension. Take your spool and gently pull thread off of it noting if there are any spots with a slight tension change like say it catches at one spot. This will translate to your stitches having momentary spots of very high top tension. I had a spool that was junking up on the bottom, top of the spool fed fine but bottom would stick and it would reak havic with my machine.