Cobra Class 26 problem

[Attackrabbit]

Hello everyone, 

I'm new to this forum and new to leather sewing machines. I finally saved enough and bought a cobra class 26. It came in and I got it set-up and started sewing. Stitches on top looked good but large loose loops on the bottom. Many youtube videos later and I started adjusting the top tension. 

The bottom did get better but still wasn't pulling the knot into the middle. Called the leather machine co. and he talked me through a few things but still didn't solve the issue. I changed needle and thread, still no better. 

I figured out how to adjust the bobbin tension so I loosened it and the stitch looks much better but now the bobbin has almost no tension (freely pulls out) and the top tension is almost all the way tight. I also noticed last night that the top thread is fraying as well. 

Eventhough the stitch looks better I think something is still not right. 

Anyone have pearls of wisdom?

Thread #138 (bought from springfield leather.  Not sure on brand)

Needle #22

[kgg]

5 hours ago, Attackrabbit said:

Needle #22

Personally I think the #22 needle is to small and really is meant for V92 in thick materials.

5 hours ago, Attackrabbit said:

I changed needle and thread, still no better. 

Who is the manufacturer of the needle?

5 hours ago, Attackrabbit said:

I also noticed last night that the top thread is fraying as well. 

A lot of times thread fraying is cause by a burr in the top thread path, too small a needle for the thread size, needle inserted incorrectly, timing off.

5 hours ago, Attackrabbit said:

I figured out how to adjust the bobbin tension so I loosened it and the stitch looks much better but now the bobbin has almost no tension (freely pulls out) and the top tension is almost all the way tight.

Did you do a drop test for the bobbin tension? Hold the bobbin case with the bobbin threaded in the palm one hand and the thread coming out tensioner. Make sure the bobbin is installed correctly and unwinds in the correct direction in the bobbin case for your machine when you pull on the end of the thread. Hold the end of the thread and lift it straight up. If the bobbin thread unwinds and the case is still in your hand tighten the tension screw. If the bobbin case lifts easily off your hand loosen the tension screw. You should be able to lift the bobbin case off your hand and with a little jerk the bobbin thread should unwind slightly and fall back into the palm of your hand. The thread tension screw probably should be adjusted in or out by about a 1/16 of a turn.

I would get the bobbin tension set correctly first then i) remove the top thread from the machine right back to the spool ii) rethread the top thread iii) start adjusting the top tension.

The Cobra 26 is a clone of the old Juki LS-341 so I would follow those threading instructions. It does differ from that of the what Cobra does on the top thread path. Refer to Section 9 THREADING THE MACHINE HEAD. I have attached a pdf of the manual.

A few photo's of your thread path from the spool to the tip of the needle would help.

kgg

 

Juki LS-341N Instruction Manual-3.pdf

[shoepatcher]

Go to a #23/160 needle with #138 thread.  All I use and I sew almost the time.  I also use titanium coat needles which are the best!

glenn

[Attackrabbit]

Thanks everyone. I am using the schmetz needles. I will order the size 23 to see if that helps. I'll also check everywhere the thread touches anything to check for burs. 

[MtlBiker]

@Attackrabbit - Just wanted to add my two cents (Canadian!)...

Needles are cheap and should be changed quite often, at least once per project and sometimes even more often than that.  From the sounds of it, I'm guessing you don't have much of a stock of needles.  Needles are so cheap that you really should have several packs (of 10) on hand and also different sizes.  And as well, a selection of regular and leather needles.  There are times you will want to size up (even sometimes down) from what is usually recommended for your thread.  I get my needles from Wawak.com who usually have the best prices, especially when they have a sale.

The other thing I wanted to mention is that when all else is properly adjusted... bobbin tension, proper threading and upper tension, if your upper thread is fraying there's a good chance it's a bad/worn out needle.  On one of my machines when the top thread starts fraying it's always been the needle.  Install a new needle and all is well.

Good luck!