Cobra class 4 reverse issues

[StoneBuiltKnives]

Hello. If I could humbly request some assistance. I recently acquired a Cobra class 4 sewing machine second hand. This is my first sewing machine of any kind. My machine is breaking the upper thread and missing stitches when used in reverse. I believe the timing to be correct but I could be mistaken. In sews fine forward. Thank you in advance! 

[shoepatcher]

we need a video of the machine sewing please.

glenn

[StoneBuiltKnives]

https://youtu.be/XqRU8rubNLA

 

 

 

[CowboyBob]

When you check the timing make sure you have the stitch length on 0 & also make sure the feed dog is evenly set front to back in the needle plate on 0 stitch too.

[kgg]

2 hours ago, StoneBuiltKnives said:

My machine is breaking the upper thread and missing stitches when used in reverse.

Couple of additional questions:

i) What thread size are you using?

ii) What size of needle are you using?

iii) Are you using the same size thread in the bobbin as you are in the needle?

iii) Have done a test of the stitches in forward verses the stitching in reverse? This is done simply by putting a piece of paper (heavier stock or cardboard) under the presser foot as if you were going to sew but without the thread in the needle. Sew as normal for a few of inches and then reverse. This will tell you if the forward and reverse stitch is the same as the needle should fall into the same holes as what was made in the forward direction. It will also tell you that the stitch length you have selected is actually what you are getting.

kgg

[StoneBuiltKnives]

Thank you for the replies. I believe I may have it fixed. I think I underestimated the tolerance for an out of time condition. The hook was just barely protruding at bdc. I adjusted it so it was flush with the housing and so far it is stitching in reverse correctly. I'll update this post if wrong. Thank you again! 

[StoneBuiltKnives]

I spoke too soon. The issue now seems to only occur when back stitching. I'm using 270 thread top and bottom with a 25 needle. Stitching length is consistent from forward to reverse. Am I trying to cram too many stitches into a small area? Again thank you in advance. I'm certainly not sure if this is simply operator error. 

[kgg]

5 hours ago, StoneBuiltKnives said:

I spoke too soon. The issue now seems to only occur when back stitching. I'm using 270 thread top and bottom with a 25 needle.

The #25 needle is good for T270 in thinner / less sticky / less tough materials so go up one size to give a little extra spacing in the hole for the top thread to be able to pull up the bobbin thread. Since most times you will be reversing to lock a stitch the problem will be even worse if the forward and reverse stitches don't match.

A good reference chart for thread size versus needle size can be found at www.tolindsewmach.com/thread-chart.html compliments of Toledo Industrial Sewing Machines.

kgg

[StoneBuiltKnives]

8 minutes ago, kgg said:

The #25 needle is good for T270 in thinner / less sticky / less tough materials so go up one size to give a little extra spacing in the hole for the top thread to be able to pull up the bobbin thread. Since most times you will be reversing to lock a stitch the problem will be even worse if the forward and reverse stitches don't match.

A good reference chart for thread size versus needle size can be found at www.tolindsewmach.com/thread-chart.html compliments of Toledo Industrial Sewing Machines.

kgg

Thank you. I'll try that.

[Burkhardt]

Another thing I noticed is get rid of the death grip on the thread and let the material feed naturally. You don't to pull the thread just hold in place for the first couple stitches then let it go. How tight are the stitches (tension) and where is the knot placement, is it evenly centered? Re watched and found another problem, when you start regardless of direction the thread should be held out in front of arm and slightly to the right. The way you're holding it is maybe the reason it's breaking because no matter the direction of sewing the hook spins in the same direction and it's probably catching the tail and winding it around the hook till it breaks.

[Constabulary]

lowering the needle bar just a tiny bit sometimes helps

EDIT:

BTW maybe this video by LW member UWE helps to figure issues with reverse:

 

Edited October 11, 2022 by Constabulary

[StoneBuiltKnives]

5 hours ago, Burkhardt said:

Another thing I noticed is get rid of the death grip on the thread and let the material feed naturally. You don't to pull the thread just hold in place for the first couple stitches then let it go. How tight are the stitches (tension) and where is the knot placement, is it evenly centered? Re watched and found another problem, when you start regardless of direction the thread should be held out in front of arm and slightly to the right. The way you're holding it is maybe the reason it's breaking because no matter the direction of sewing the hook spins in the same direction and it's probably catching the tail and winding it around the hook till it breaks.

Thank you. The knot seems to be centered in the material and tension seems to be about right to my untrained eye. I appreciate the feedback about the way I'm gripping the thread!

[StoneBuiltKnives]

2 hours ago, Constabulary said:

lowering the needle bar just a tiny bit sometimes helps

EDIT:

BTW maybe this video by LW member UWE helps to figure issues with reverse:

 

Thank you. I'll try lowering the needle bar a millimeter or so. That video is illuminating!

[cashmanleather]

I have a Cobra 4 and I've had to shim the selector plate to get the needle to hit the same holes in reverse on mine. 

[StoneBuiltKnives]

1 hour ago, cashmanleather said:

I have a Cobra 4 and I've had to shim the selector plate to get the needle to hit the same holes in reverse on mine. 

My machine seems to hit the same stitching holes fairly consistently from forward to reverse. At the this point I'm waiting on 26 needles to try. If that doesn't solve the problem I'll try lowering the needle bar a smidge. I don't want to make multiple changes at once.

[Burkhardt]

4 hours ago, StoneBuiltKnives said:

My machine seems to hit the same stitching holes fairly consistently from forward to reverse. At the this point I'm waiting on 26 needles to try. If that doesn't solve the problem I'll try lowering the needle bar a smidge. I don't want to make multiple changes at once.

Did holding the thread forward and to the right when starting help? I mean putting your arm through the arm gap and hold the thread forward and to the right.

 

[StoneBuiltKnives]

It helped enough for me to believe it was part of the problem. Specifically with missing stitches. I'm still getting some thread fraying, though no full breakages yet.  Thank you.

[Burkhardt]

2 hours ago, StoneBuiltKnives said:

It helped enough for me to believe it was part of the problem. Specifically with missing stitches. I'm still getting some thread fraying, though no full breakages yet.  Thank you.

Another thing is to who suggested going to a bigger needle is right and whether true or not I've read on a lot of forums and everyone points the finger at black thread that because it is is dyed so long to get the full color that it makes it a PITA to sew and everyone says go with a bigger needle. A video is worth a thousand words that every time I watch it I find something else. Just got a roll of black thread so I know what to watch for.

[StoneBuiltKnives]

I'm inclined to believe a bigger needle is needed as well. The problem gets worse the thicker the leather I sew. When I get to my three layers of 8 oz glued is when I have the worst problems.

[CowboyBob]

15 hours ago, StoneBuiltKnives said:

I'm inclined to believe a bigger needle is needed as well. The problem gets worse the thicker the leather I sew. When I get to my three layers of 8 oz glued is when I have the worst problems.

Have you tried increasing the foot pressure?

[StoneBuiltKnives]

1 hour ago, CowboyBob said:

Have you tried increasing the foot pressure?

I did not but it's already leaving marks in my leather.

I have however  finally achieved some success with my sewing woes. I didn't realize I had lighter thread in the box of stuff I got with my machine. I dropped down to a 207 thread with the 25 needles and my breakage problems disappeared. Thank you for all the assistance. Now I can focus on learning to actually use the machine instead of troubleshooting.

[StoneBuiltKnives]

Finally!

[RockyAussie]

Looks good to me.

[StoneBuiltKnives]

7 hours ago, RockyAussie said:

Looks good to me.

Thank you!

[Doc Reaper]

I had a problem of thread breaking on 3 different machines (not the same make) and I was missing stitches. I checked to make sure it was threaded properly, the tension was slightly adjusted to make sure that wasn’t a problem. So I got to thinking about what would  fray the thread? 
 

i checked for burrs and sharp edges everywhere around the needle and plate areas, all was good. I eliminated everything but the needle! So I changed the needle , still using the same size - still the same problem, UGHH!

So I watched the operation of the needle closely, and the thread was not even, like it was cut by scissors, but even enough to be happening at one spot - the eye of the needle (where the thread goes thru). 
Not all at once but the thread was bunching on the feed side of the needle and the fibers of the thread kept popping one at a time! So I got a needle with a larger hole and my problem vanished!

needle size charts were made when materials for thread and needle were different. I ALWAYS go to the next size up in needles, it helps cut down on frustration!  I even made that comment to Cowboy Bob when I made an order about 3 weeks ago. 
So if you are fraying right at the needle, increase to the next needle size up 

Edited October 14, 2022 by Doc Reaper