Cobra Class 4 tension - how to

[masheed]

I recently bough Cobra Class 4. Seller convinced me that it is a perfect machine for leather work. I mostly I need to sew leather patches on the hats. Today is the first time I am running the machine stitch samples. However, there is an issue with the tension and I see bobbin thread pull up  and the piece of swatch has waves .  Is  the issue related to bobbin thread tension. Machine came pre adjusted tension for 1 inch thick leather. I am going to sew on 4mm thickness. Is this going to be an issue?

Thanks your feedback 

Edited October 17, 2022 by Northmount
Changed title

[Northmount]

@masheed Fixed the title of your post and moved it to leather sewing machines.  You are much more likely to get help here.

 

[kgg]

 

22 hours ago, masheed said:

Is  the issue related to bobbin thread tension. Machine came pre adjusted tension for 1 inch thick leather. I am going to sew on 4mm thickness. Is this going to be an issue?

A couple of questions:

1. What size of thread are you using?

2. What size of needle are you using?

The Cobra class 4 is a 441 class machine and this class of machine shines at sewing thick stuff with heavier weight thread up to 7/8" thick. The min thickness this machine is listed at is 6 oz leather (4.5mm) and you are wanting to sew 4mm or 5.5 oz leather so you are just a touch below.  There a couple of articles by Wiz on what adjustments you may have to do in order to sew thinner material and RockyAussie has a needle plate designed to help with sewing thinner stuff.

I am not saying it won't sew that thin but I think a class 341 like the Juki LS341 / 1341 machines or Cowboy 341 or Techsew 2750 would probably have been a better choice. 

kgg

[TomE]

Here are links to the information that @kgg mentioned above.  I use the narrow feed dog and plate for everything on my Cobra Class 4 and find it easier to switch between heavy and lightweight leathers.

https://www.rw-leatherworks.com/blog/2019/02/dumbing-down-a-cowboy-cb4500-cobra-class-4-or-similar-harness-stitcher.html

 

[Wizcrafts]

11 hours ago, TomE said:

Here are links to the information that @kgg mentioned above.  I use the narrow feed dog and plate for everything on my Cobra Class 4 and find it easier to switch between heavy and lightweight leathers.

https://www.rw-leatherworks.com/blog/2019/02/dumbing-down-a-cowboy-cb4500-cobra-class-4-or-similar-harness-stitcher.html

 

Thank you very much for linking to my blog article! I know it has helped a lot of people with 441 clones.

I also use the narrow feed dog and throat plate made by RockyAussie. It does it all so far. I do have another custom feed dog and plate that I need to install and try out. It is more limited though and is strictly for smaller needles.

[TomE]

1 hour ago, Wizcrafts said:

I do have another custom feed dog and plate that I need to install and try out. It is more limited though and is strictly for smaller needles.

Look forward to hearing about this custom feed dog/plate.  I am on the lookout for methods to machine sew bridles that I now sew by hand.  I have a Cobra 4 and don't see myself buying a second machine at present for my tack making hobby.  9-10 oz leather with #207 thread @ 9-10 SPI.  Particularly interested in how to navigate along the edge of a swelled noseband. 

[RockyAussie]

6 hours ago, TomE said:

I am on the lookout for methods to machine sew bridles that I now sew by hand.  I have a Cobra 4 and don't see myself buying a second machine at present for my tack making hobby.  9-10 oz leather with #207 thread @ 9-10 SPI.  Particularly interested in how to navigate along the edge of a swelled noseband. 

Hey @TomE, I am wondering if the right side paddle foot would work for you. With the narrow needle plate set and it you can get pretty darn close to the edge as you can see in this picture where I am stitching a oil stone pouch.

Other than that an inline foot set should work as well or better I think. I do not do horse tack myself but with the 207 thread and the needle that that needs I would have thought 9/10 SPI would be getting a bit too close

I hope to get to see how it goes.

Regards Brian

[TomE]

1 hour ago, RockyAussie said:

Hey @TomE, I am wondering if the right side paddle foot would work for you. With the narrow needle plate set and it you can get pretty darn close to the edge as you can see in this picture where I am stitching a oil stone pouch.

 

Other than that an inline foot set should work as well or better I think. I do not do horse tack myself but with the 207 thread and the needle that that needs I would have thought 9/10 SPI would be getting a bit too close

I hope to get to see how it goes.

Regards Brian

The paddle foot might be worth a try.  For raised leather pieces, I have used an inline presser foot.  It requires a bit more border than I want on the finished piece but I can trim after sewing.  For swells that taper continuously and have no border along the edge I am uncertain how to sew them on a machine.  The process of forming the swell by skiving and shaping 2 layers in a rounding block is not conducive to leaving a border that can be trimmed after sewing.  Additionally, the padded liner sewn on the bridle pieces would interfere with trimming the edges after sewing.  I guess this bridle is designed to be hand sewn. 

I agree that for machine sewing at 8+ SPI I would need to use a smaller thread and needle.

 

Edited October 18, 2022 by TomE

[Wizcrafts]

4 hours ago, TomE said:

For swells that taper continuously and have no border along the edge I am uncertain how to sew them on a machine...

If you can't sew these seams with a paddle or inline foot, find a shoe repair shop and pay them to sew it on a curved needle sole stitcher. It does need about 1/4 inch of space from the raised sides, just like a shoe might have.

[RockyAussie]

9 hours ago, TomE said:

I guess this bridle is designed to be hand sewn. 

Oh yea of little faith, You in the wrong forum section if a you going to use language like that. Sometimes the answer is in the formula. If the swell is made of the right sort of rubber/foam it will sit down under the pressure of the foot and bounce back up as you sew along. There is also another special foot set that may be hard to obtain but it allows you stitch around the welts on shoes. Lots of adjustments with those so I would try the paddle feet first. Could you load any pictures of the bridle pieces?