Stitching Troubleshooting Cobra Class 4

[bland]

I recently (one month ago) got a Cobra Class 4 machine and I haven't been able to get it adjusted correctly yet.  Is there a troubleshooting guide out there that shows pictures that say if your machine is doing this then try this?  

I did 3 passes the first two left to right and the 3rd right to left.  I changed the needle between the first and second pass.  Thread size 277 needle size 25 (passes 2 and 3 with S point)on a single layer of 12oz saddle skirting.  The back side looks pretty good but the front looks awful.  

 

 

[Wizcrafts]

First of all, 12 ounces is really light for #277 thread. It is hard to hide the knots that are fairly large, as you can see. But, the knots should not be changing altitude in a continuous stitch line. Something is intermittently letting go or tightening up and causing the knots to move up and down. Let's consider the usual suspects. Investigate these one at a time until you identify your culprit.

1. Improperly wound bobbin, or bobbin inserted feeding the wrong way. Try reversing the bobbin orientation.
2. Thread fragment under the bobbin tension spring business end, causing the bobbin tension to drop as the thread feeds past the scrap.
3. Out of round bobbin ends
4. Moving up ^^^ top thread is over-bonded and comes off spool like a coil spring, changing its tension as it feeds or binds along the path, then lets loose.
5. Top thread not staying centered in the top tension disks, thus changing the tension. This can be caused by twisty thread.
6. Needle too big for thread/thickness combination. Try a #24 needle.
7. Thread too thick for thickness being sewn, Try #207 thread instead, with a #24 needle
8. Top thread flipping over guides or rollers on the way to the needle.
9. Rawhide or weak sections in the leather can affect the stitches.

It is obvious that the problem is too much tension on top and not enough on the bottom. You might solve the problem by tightening the bobbin tension screw a bit, then compensating with the top tensioner. This is a big boned machine that doesn't mind being rode hard.

[bland]

Okay, I tried a few things.

1. Bobbin was good.  Cleaned to bobbin case and checked for foreign matter.  

2. Adjusted holder moved cones up higher and made sure it was coming straight off the top.

3.  Used different thread and needle sizes.  

4.  Loosened the presser foot chain.  I noticed it was pulling a little when machine was running.  

Passes 1-4 on 14-16 oz saddle skirting.

Pass 1 is size 24 needle with 277 nylon thread for top with 346 nylon thread in bobbin.  Pretty pleased with top.  

Pass 2 24, 277, 277.  Pretty pleased stitches are a lot more uniform.  

Pass 3 size 24 needle 207 polyester top and 277 bobbin.  Fairly consistent but bubbles pulling up from bottom.  

Pass 4 size 23 needle 207 poly top and bottom.  Consistent but bubbles showing up on top

Pass 5 and 6 on 10 oz saddle skirting.

Pass 5 size 23 needle 207 poly top and 277 nylon bottom.  Consistent bubbles on top.  

Pass 6 size 24 needle 277 nylon top and bottom.  With bubbles on top.  

The upper tension is as loose as I can make it.  Still skips some stitches on reverse.  I''m sure all is just operator error.  Any suggestions are appreciated.  

 

 

[sheathmaker]

Don't want to beat a dead horse, but if you did everything you saId and are still getting the bobbin pulled up like on pass 6, then there has to be a bind somewhere in the thread track from spool to needle.  A silly question, but are you sure you threaded the machine correctly?  What you are experiencing is quite common with the thread track from spool to needle hanging up on a screw, or an unintentional extra wrap around the secondary tension on the way to the take up arm, or a little bit of bind going through the last "screw" loop or the last hole before the needle.  I have had similar temporary problems, but they all traced back to pilot error and a bind somewhere in the thread track.

I know it's frustrating.  I'd give Steve a call and see what he might suggest.

Good Luck

Paul

[RockyAussie]

2 hours ago, bland said:

The upper tension is as loose as I can make it.  Still skips some stitches on reverse.  I''m sure all is just operator error.  Any suggestions are appreciated.  

You are reducing both top tensions? It is common to run a next size thread smaller in the bobbin than the top or the same size but I don't think I've heard of running a thicker on the bottom before. Consistency is at least a good sign.You may need to tighten the bobbin spring on the lighter threads a bit. Brian

[brmax]

I think the first two stitch lines are working better. The idea to use a bigger thread in the bobbin than top has my interest in why.

Im curious is the bobbin tension screw still adjustable. Not to make a change at this time in your test, just the question.  A reason I ask is you mention the top tensions being at their minimum setting.  

I know these 441 types are heavy duty,  I have been curious if top tension springs are an option some have changed.  

Good day there

Floyd

[bland]

On 8/19/2017 at 8:30 PM, sheathmaker said:

Don't want to beat a dead horse, but if you did everything you saId and are still getting the bobbin pulled up like on pass 6, then there has to be a bind somewhere in the thread track from spool to needle.  A silly question, but are you sure you threaded the machine correctly?  What you are experiencing is quite common with the thread track from spool to needle hanging up on a screw, or an unintentional extra wrap around the secondary tension on the way to the take up arm, or a little bit of bind going through the last "screw" loop or the last hole before the needle.  I have had similar temporary problems, but they all traced back to pilot error and a bind somewhere in the thread track.

I know it's frustrating.  I'd give Steve a call and see what he might suggest.

Everything seems to be coming off smooth without hang ups.  I checked and I am threading correctly based on a couple different sources.  I am sure it is pilot error.  I tried to call Steve on Friday but no one was in the shop when I called and it is usually after hours when I get off my regular job.  I have been sending him photos as well.    Early on I ran it for a while with only one wrap around the primary instead of the recommended two.  It worked okay but is not as consistent.  

On 8/19/2017 at 8:58 PM, RockyAussie said:

You are reducing both top tensions? It is common to run a next size thread smaller in the bobbin than the top or the same size but I don't think I've heard of running a thicker on the bottom before. Consistency is at least a good sign.You may need to tighten the bobbin spring on the lighter threads a bit. Brian

I am reducing both tensions.  Running the larger thread on the bottom leaves the back raised a little, it doesn't look as good as it should.  

On 8/20/2017 at 7:38 AM, brmax said:

I think the first two stitch lines are working better. The idea to use a bigger thread in the bobbin than top has my interest in why.

Im curious is the bobbin tension screw still adjustable. Not to make a change at this time in your test, just the question.  A reason I ask is you mention the top tensions being at their minimum setting.  

I know these 441 types are heavy duty,  I have been curious if top tension springs are an option some have changed.  

I will check the bobbin screw again and see if there is any adjustment left.

Wiz, Paul, Wild Harry and Floyd thanks for your responses and ideas on what to check.  I think I''m getting closer to getting things adjusted.  Hopefully there is still a little adjustment in the bobbin and it will all look good.  I'll check a few more things and test it again.  

Thanks again to all!!

[bland]

Here are more results from this evening.  I adjusted the bottom tension a couple of times but when I tried to tighten the top a half turn bigger bubbles showed up again.  The test leather started to drop off a little in weight.  With the smaller thread the tension is pulling the knot out the top still a little.  It is much better than when I started.  

[CowboyBob]

Yes,it's looking better BUT ,I always tell people when your checking tension to make sure your leather is thick enough for the thread,so you should try the larger thread on 2 layers or the thickness of the project you plan to sew.And practice alittle on that thickness before you try sewing on a piece that has tooling & is cut to size,it a lot easier than pulling out stitches or possibly having to start over.

You can see that's why the 277 & 207 combo looks better than the 277 & 277 the thinner thread on the bobbin helps to hide the thread therefore making your stitch look better as you get into thicker the 277 & 277 will look better.I know a lot of people always run a size smaller in the bobbin when they are sewing on  thinner leather.277 is best when your around  3/8" & thicker the knot hides better.

[bland]

2 hours ago, CowboyBob said:

Yes,it's looking better BUT ,I always tell people when your checking tension to make sure your leather is thick enough for the thread,so you should try the larger thread on 2 layers or the thickness of the project you plan to sew.And practice alittle on that thickness before you try sewing on a piece that has tooling & is cut to size,it a lot easier than pulling out stitches or possibly having to start over.

You can see that's why the 277 & 207 combo looks better than the 277 & 277 the thinner thread on the bobbin helps to hide the thread therefore making your stitch look better as you get into thicker the 277 & 277 will look better.I know a lot of people always run a size smaller in the bobbin when they are sewing on  thinner leather.277 is best when your around  3/8" & thicker the knot hides better.

I did this late last night before I saw Bob's comment.  Anyway this is 2 x 8 oz (16 oz) leather with 277 on top and bottom.  

 

[CowboyBob]

Looks pretty good,but if you had the 207 in the bobbin it would hide the knot better.

[Wizcrafts]

48 minutes ago, CowboyBob said:

Looks pretty good,but if you had the 207 in the bobbin it would hide the knot better.

And weaken the stitch strength to that of the thinner #207 thread. This is where trade-offs happen in the leather sewing business. If one sews a gun holster with #207 thread in the bobbin, there is no point in using anything larger on top, except for appearances.

A properly balanced tension system on a 441 type machine should easily hide the knots of #277 thread between two layers of 8-9 ounce leather. If the knots keep moving up and down, either the spool of thread is poorly bonded, or is twisty coming off the spool, or the top thread is lifting and lowering inside the top tension disks, or the check spring action is too strong, or the bobbin spring is worn where the thread feeds out of it, or there is crap in the bobbin case, or the bobbin thread starting stub sticks out and interferes as the bobbin turns inside the case, or the bobbin length or end shape is out of specs.

[jrprottas]

I'm also in the process of learning about my new Cobra Class 4. 

It takes quite a bit of force to pull my workpiece out of the machine. Videos make it look very smooth and easy. What am I doing wrong? Which tension points might be the culprit?

Also, do schmetz needles have some size identification on the needle itself?

Thanks, Jeff

[Hildebrand]

@jrprottas make sure you are stepping down hard on the pressor foot release peddle.  When you push it all the way down it releases the top tension, also on videos I have watched they sometimes grab the thread on the end of the machine and pull down creating slack so you can pull the work out easier.

Todd

[Wizcrafts]

1 hour ago, jrprottas said:

It takes quite a bit of force to pull my workpiece out of the machine. Videos make it look very smooth and easy. What am I doing wrong? Which tension points might be the culprit?

Jeff, when you push all the way down on the foot lift pedal the top tension disks should be opened up by a lever underneath them that gets pushed up. Examine the tension disks while somebody pushes down on the pedal to see if this is happening. If the lever does move up into the disks but they don't open it could be that the tension spring has been tightened so far that it has no more give to let the disks separate. If so, back off the top tension spring and back off the bobbin tension to balance the knots.

The hand lift lever, with the ball end, should also provide enough lift to separate the tension disks.

Sometimes new 441 clones are setup with fairly high bobbin tension. I recommend backing it off until there is a smooth flow with a little spring tension, but not free flowing. This will give much more range of adjustment on the top disks and lower roller.

If the top and bottom tensions are not too tight and the disks are opening with the lifters but the thread is very tight, check the thread path to see if it is twisted around a guide, or caught under the thread spool. If the thread is looped around the top post, try just feeding it straight through the upper hole, or even sideways through the second hole, but not through any other holes. This will relieve a lot of thread tension, depending on the stiffness of the thread.

[CowboyBob]

Don't forget to always stop & start with the take up lever @ the highest point,to make sure the needle thread is released off of the bobbin.

CB441 manual pg5.pdf

Edited January 2, 2020 by CowboyBob

[dikman]

On 1/1/2020 at 3:47 AM, Wizcrafts said:

Sometimes new 441 clones are setup with fairly high bobbin tension.

My new CB4500 was like that, it took a lot of force to pull the bobbin thread, I had to back off the tension a bit.