Cobra class 4: 346 bonded polyester thread? Help!

[Wizcrafts]

3 hours ago, Patrick1 said:

Did you ever lubricate the presser foot bar inside the cover since you purchased the machine? It will stick or not move as freely giving a false pressure adjustment so you end up over compensating the pressure.

This is an important, often overlooked issue for most sewing machines, but especially the 441 clones. I have a long-time buddy who bought a Cobra Class 4. After a few years the presser and alternating foot bars started getting stuck in the up position. He added more foot pressure to get them to drop, marking the leather even worse. He had me come over to troubleshoot it and I unthreaded the machine and removed the front cover plate. IIt was dry inside and there were scoring marks visible. I removed the presser bar and pulled it through Emory cloth to get the marks off. After putting it back together, I oiled every moving part. The machine worked perfectly afterward. So, remove the front cover and oil every crank and rod that moves against or through something.

[DieselTech]

3 hours ago, Patrick1 said:

Did you ever lubricate the presser foot bar inside the cover since you purchased the machine? It will stick or not move as freely giving a false pressure adjustment so you end up over compensating the pressure. The presser foot you are using spreads the pressure lengthwise vs widthwise as in @RockyAussiewelded foot.

 

22 minutes ago, Wizcrafts said:

This is an important, often overlooked issue for most sewing machines, but especially the 441 clones. I have a long-time buddy who bought a Cobra Class 4. After a few years the presser and alternating foot bars started getting stuck in the up position. He added more foot pressure to get them to drop, marking the leather even worse. He had me come over to troubleshoot it and I unthreaded the machine and removed the front cover plate. IIt was dry inside and there were scoring marks visible. I removed the presser bar and pulled it through Emory cloth to get the marks off. After putting it back together, I oiled every moving part. The machine worked perfectly afterward. So, remove the front cover and oil every crank and rod that moves against or through something.

Yes I think this is what happened to me. I think the needle bar & presser foot bar were stuck in the up posisition or stuck in general from sitting soo long & collecting dust. 

I have since then backed the presser foot pressure off by 10 full turns out. Now it is not marking the leather up as bad. I Think my presser foot pressure is still a bit high. 

I will find a video on removing the said plate you 2 are referencing & lubricate things. 

The tolerances must be real tight on the needle bar shaft & the pressure foot shaft. 

Thanks. I'm getting ready to make a couple more practice runs. Soo I will report back. 

[DieselTech]

Soo I went ahead & removed the side/front plate, whatever you wanna call it. 

But does Cobra/Leather Machine Co. even mention all the oil holes under that cover in their oil maintenance schedule. I should of took some pictures. 

But there must be like 7-9 more oil holes/spots to oil the linkage & bars under the cover. Point taken for sure now. 

Ok I'll run a piece of leather thru in a bit & post results. 

[DieselTech]

Ok. So I removed side/front plate & lubed everything. 

Then I went & glued up exactly what I would be using for the rear flank billets. 

I then switched to a #25 S point needle. I increased stitch length to exactly 5 stitches per inch. 

I adjusted my presser foot pressure to 6 full turns out, from where I originally had the machine before putting it away. 

I think I could decrease my presser foot pressure some more. 

Also how do you guys fudge a stitch? When coming around to your original start point? 

Wether you need to fudge a shorter/ or longer stitch to meet in the original needle hole you started at? 

Thanks. 

[kgg]

5 hours ago, DieselTech said:

I would think the #25 needle I was using is big enough. That 346 lubricated poly thread falls thru the needle eye like throwing a hot dog down a hallway. 

The question: The V346 may slide nicely through the eye of the needle but... is the hole made by the needle large enough to allow for the V346 (top and bobbin) from being caught by the leather as this would become more critical as the thickness of the item being sewn due to more surface area that could act as a catching point???

kgg

[RockyAussie]

10 hours ago, DieselTech said:

But there must be like 7-9 more oil holes/spots to oil the linkage & bars under the cover. Point taken for sure now. 

Another point that seems to get missed is the foot presser adjuster has a large funnel shape in it. Guess why? A couple of drops can work wonders in there. Also some times the adjuster is not exactly straight with the shaft so it is worth checking by lifting the feet when doing the adjustment to feel for any binding. Doing the lock nut on it can also make it sit crooked and bind up.

[DieselTech]

8 minutes ago, RockyAussie said:

Another point that seems to get missed is the foot presser adjuster has a large funnel shape in it. Guess why? A couple of drops can work wonders in there. Also some times the adjuster is not exactly straight with the shaft so it is worth checking by lifting the feet when doing the adjustment to feel for any binding. Doing the lock nut on it can also make it sit crooked and bind up.

I will have to keep a eye out for the adjuster getting crooked from the lock nut. 

I knew about the dished adjuster to aid in oiling from some vids I watched. 

Thanks. 

[cashmanleather]

You have to use as large a needle as needed without catching. You can also run it through some thread Lube. When you're all done take a flat shoe hammer or something with no marks on it and tap the stitches all the way around. It'll set everything and closeup the holes

Edited October 22, 2024 by Northmount
fixed typo