Class 26

[MarkNY]

I have a cobra class 26. I don’t use it very often because I can’t seem to dial in the settings. Not sure how to post a photo here. Sewing through approx 12oz I can get it to sew ok on a test piece but when I sew my project it’s a mess. It’s not walking evenly, knots are showing on top. It’s a mess. Any ideas? Thanks 

[Docado]

Look up 

“Tips and Tricks for Cobra Class Equipment “

explain your problem and someone will help you. 

[bruce johnson]

Is your test piece the same leather and thickness as your project pieces? If so it's odd that the test piece sews that much differently than the project. Needle size and thread size appropriate? Same bobbin on the test piece and project? Thread path not binding on top and thread coming off the top spool cleanly? These are what I check first on our machines. Otherwise I'd be on the phone Monday with Vince and have him talk you through it. 

[kgg]

1 hour ago, MarkNY said:

knots are showing on top.

Getting the tension right, is sort of like a tug of war. When the knots are on the top chances are the bobbin tension isn't correct.

Basic needs:

1) Quality thread like A&E. Typically use the same size thread for the top thread and for the bobbin.

2) Quality needles like Schimetz Needles. Use 135 x17 x Needle Size for fabric and 135 x 16 x Needle Size for Leather.

3) Needle size to be correct for the size of thread selected. Needle size verses thread size chart ( https://www.tolindsewmach.com/thread-chart.html )

4) Bobbin Tension needs to be correct for thread size and using the drop test method would work. Any adjustment to the bobbin tension should be done in small amounts on the bobbin case holder thread tensioner screw like 1/8 turn in or out at a time. Over tightening of this screw will bend the bobbin case holder thread tensioner and require it to be replaced. I find getting this tension right first makes it easier then you only have to worry about the top thread tension.

5) Correct thread path from the thread spool to the eye of the needle. If the thread path is incorrect you will never get consistent top tension.

6) Know the sewing limits of your machine. I think the Cobra Class 26 is very similar to that of the Juki LS-341/1341. So it should be able to sew close to 1/2" thick material but that maybe reduced depending on the toughness of the material and the thread size / needle size combination you select.  

A little more info would be helpful:

1) thread size

2) needle size

3) few photo's of your thread path

4) few photo's of the sewing

Or

Make a video, put it on Youtube and give a link.

kgg

[MarkNY]

Thanks for the comments. I don’t know how to post pictures here, wish I could. This machine is essentially new. I guess I better start fresh and do initial setup again. I have 2 other machines (not cobras) that I just hop on and use without issue but I haven’t been able to do that with this one. I’ll update with needle size etc 

[Northmount]

2 hours ago, MarkNY said:

I don’t know how to post pictures here, wish I could.

What device are you using so we can give you some tips?

[MarkNY]

4 hours ago, Northmount said:

What device are you using so we can give you some tips?

I’m using an iPhone. File size is big! 

[Northmount]

 

4 hours ago, MarkNY said:

I’m using an iPhone. File size is big! 

If your files are too large to post here due to file size restrictions, you need to resize your files to fit.  Follow this link for some helps and suggestions.  https://leatherworker.net/forum/topic/15122-how-to-post-pictures-on-lw/?do=findComment&comment=551171 There are lots of Apps, software, and online tools available on the web, or even built into your device to enable you to reduce your file sizes.  800 pixels in the longest dimension is quite adequate.  Smart phone screens and many monitors don't display high res files in high resolution.  People that live on the fringes of the internet appreciate smaller file sizes and high res photos may take from 10 minutes to hours to download.

 

[Wizcrafts]

@MarkNY

Did you glue or tape the layers together and is the needle going through the glue or tape? This can cause tension problems as the eye gums up. It can also cause the top thread to rat.

Every now and then, after I've balanced the knots in a matching test strip, as I'm sewing the knots will start to show on top. When I investigate the problem, it's usually either that the bobbin thread has loosened, or twisted out of the tension spring, or the top thread twisted and got snagged along the way and became too tight. Things can change during active sewing, especially when you start, stop, speed up and slow down.

Another thing to check is the presser foot pressure setting. There should be enough pressure to keep the leather from lifting with the ascending needle.

If you have trouble balancing the knots, use the smallest needle that centers the knots. An oversize needle lets the knots move at the slightest provocation. Note that the tighter hole will require more top tension to bring the bobbin thread up. This may help if your leather has inconsistent density, or is glued or taped and it is sticking to the needle.

Make certain that you are loading your bobbins evenly. I usually load them in so the thread makes a sharp turn as it feeds the slot in the bobbin case. This increases the bobbin tension a bit and provides better stability for staying under the tension spring. But, if there is any cross threading on the bobbin, or fuzzies, they will cause hiccups to the bobbin tension as you sew. Also, if the bobbin is out of shape, toss it and buy new ones that stay flat as they rotate.

You should be able to buy prewound bobbins from A&E and other thread companies. They are usually would to exacting specifications for commercial use. I use a lot of prewounds and rarely have any issues with them.

Finally, make sure the needle is inserted with the long rig on the left and the cutout facing due right. Oh, and use titanium coated needles if possible. The coating helps when sewing through glue and reduces heat buildup.

[MarkNY]

22 hours ago, Northmount said:

What device are you using so we can give you some tips?

I’m using an iPhone. File size is big! 

[MarkNY]

Thanks so much for the replies. I’m trying to reduce the size of my photos to show you my setup. I’m using 138 nylon thread, groz Beckert perp point size 22 needle…. Maybe I need to check my foot pressure. 

Edited Monday at 12:56 AM by MarkNY

[MarkNY]

This is 3 layers, maybe 15oz total. Number one is a crawl speed, number 2 is full speed, number 3 is in between 

Edited Monday at 12:58 AM by MarkNY