Cobra Class 4 Fraying Thread

[NewfoundlandLaw]

Hey All

 

My new Cobra Class 4 has been running like a champ since I got it in October. So far it has made about 20 sheaths and 10+ seal fur bags.  (Not to mention about 16oz's of practise 277 stitching.)

 

Tonight I accidentally bent a needle while sewing a sheath and it looks like it contacted their bottom feed plate.  It was a very light contact as I was going slow, but it looks like I marred the the piece.  It left some very small marks on the piece, but now it seems like every time I try to stitch it frayes and breaks the stitch within 2-4 stitches.  I've attached a picture of the little piece and the thread below. 
 

Is this little piece the problem?  If so, order a new one?  Also, can it be fixed with a Jewellers file while I wait for a replacement?

Edited January 14, 2020 by NewfoundlandLaw

[RockyAussie]

A bit of emery cloth would be better than the file but I would suspect that you may have knocked the timing out. Double check that the needle bar has not moved up before any other adjustments.

[dikman]

I'd just use a Dremel with a diamond or carbide bit to carefully smooth it, then wet and dry paper (wet) to take out any remaining scratches and finish off with a polishing wheel. You just want to make sure there aren't any rough edges to catch the thread.

And check the timing, as Brian said. A slightly mis-shapen hole shouldn't make any difference operationally.

[NewfoundlandLaw]

12 hours ago, RockyAussie said:

A bit of emery cloth would be better than the file but I would suspect that you may have knocked the timing out. Double check that the needle bar has not moved up before any other adjustments.

How do I check the timing?

[kgg]

37 minutes ago, NewfoundlandLaw said:

How do I check the timing?

I would check your manual. If you didn't get one call your dealer and they should be able to walk you through the process.

kgg

[dikman]

The Juki engineers manual is in this post, along with Uwe's excellent adjustment video. It's probably worth becoming familiar with the basic timing of the machine, although if it's forming stitches ok (other than fraying the thread) then it's probably still in time. First thing is to get rid of the burrs on the feed dog.

[RockyAussie]

7 hours ago, NewfoundlandLaw said:

How do I check the timing?

There was an excellent video that showed how to do a basic timing fix on this type of machine by Solar Leather but that now appears to have gone private now.

First thing I can say is check that when your needle is all the way up that there looks to be a 3mm (1/8") gap between where the needle bar shaft and the needle holder piece attach. Any much less and the needle has been knocked up. The best video I can suggest is one by our most honourable members @Uwe in this following video- https://www.youtube.com/watch?v=ZT3AVgj_HLI

Note there is a measurement early on in it that gives the height that the needle bar should be at.

[NewfoundlandLaw]

After talking to Cobra directly, I not only have the issue fixed, but my machine now makes better stitches than ever before!  Gotta say, blown away by their awesome service!

[JLSleather]

So... WHAT was the issue?

[NewfoundlandLaw]

1 hour ago, JLSleather said:

So... WHAT was the issue?

When I bent the needle I messed up the smooth feed dog and put a small burr on my timing hook. Timing was ok, but during the conversation with Cobra, I reduced my lower bobbin tension. 
 

So, not only did I get the problem fixed, I got my machine better dialled in for sheath making. 
 

WIN WIN!