new Cobra Class 4 video

[Massive]

Put up about a week ago.  I am supposed to take delivery of my machine today, so it comes at a good time.  I was able to sell my earlier walking foot only machine at what I paid for it, minus 100 I paid to smooth out the deal.  The cobra is being bought retail, so it will be a little harder to recoup the cost of when I sell, but I still think these machines are a good value both arriving at, and leaving the shop.  And they give good value working also, which is the main point.

[Marshal Will Wingam]

Good video. Thanks for posting the link.

[Red Cent]

Interesting. Much more informative than the DVD that comes with the machine. And nowhere in the DVD or the two manuals does it show the little thread hole just above the needle.

If you get the same manuals, at first it is frustrating then you get to laughing. You will see what I mean.

The machine is great. Does what it is supposed to do. Keeping the work neat is a task for the newbie. Don't blink.

Just curious, who have you been talking to at the company office?

[Cliff Fendley]

The manuals that come with it do leave a lot to be desired.

[Massive]

Manuals?  What is that?

The box came with a single sheet of paper that gives one start-up instructions on one page.  I followed that sequence though I didn't read it.  Sews fine, there are some good parts and some not so good parts.

I am not too sure about the EPS, but the rest is pretty familiar.  I will have to figure that out.  There is also a box with some weird cords and an electric eye thing, not sure where that goes.

This is my 7th leather machine, so I pretty much knew what I wanted.

Red Cent.  I didn't really talk to anyone.  Almost all my communication was trying to make a deal.

[Red Cent]

I received two manuals and a sheet of paper. One manual is jointly in Chinese and English. The other manual is, admittedly, put together by a customer.
The Leather Machine Co. needs to hire a Q & A individual to show them how to "make a peanut butter sandwich" manual.

I got a question for anyone with experience on the Cobra 4. If you have the tension adjustments so that the top stitch and bottom stitch are equally tight, please, please, send me a picture of the adjustments by e-mail. Or describe the position of the nuts on the tension adjustments. I cannot get the bottom stitch adjustment correct.

And I have tried to contact Steve for about a week.

[Massive]

To state the obvious, it has to be threaded properly, and that might sound condescending, but I don't mean it that way.  For instance a thread can get caught in the stack around the pulley, etc...

My big revalation about tension setting on all my sewing machines is that one needs to make a record of the tension on the bobbin case.  preferably when the machine is new, and working factory correct.  The way I do that on the big machines is that I take the bobbin out and the hook/case assembly , and over a soft surface, I insert a thread such as it came with, say a 270 about 36 inches of it.  I don't have the bobbin in there, but otherwise I have it exactly threaded as though the thread was coming from a bobbin.  I then try to suspend the whole hook and case assembly, and see how stiffly it slides down the thread.  The idea is to get a calibration of the tension.  Normally the hook/case assembly will not fall, but minimal jiggling will get it to slide down the thread.  I have not yet performed this test with the Cobra 4 though.  I just got mine yesterday.

What we are after is a default tension setting for the lower end.  Make a note of what that tension setting is, and mark with a fine Sharpie the screw setting.  I do this on all my bobbin cases.  I have fishing sinkers that I hang from the cases to precisely calibrate the weight that is required to slide the tension assembly down the string.

With that, and assuming 270 top and bottom; that the threading is correct; that the top thread does not accidentally go through the winding tension assembly also; that the correct needle size, not too small is in use; that the needle is squared away and the right way around; that the leather is normal, nor weird cements:

This video describes the process, even though it is for home sewing, she has a good process for the lower end.



Ok, so the two tensions screws on my just out of the box machine are set like this.  The lower one has barely one thread showing, at best 1/32" protrusion beyond the nut.  The upper has about 2 showing, at best 1/16" of thread and domed screw end is out/.  I will be marking the top center positions of these screws with black sharpie.

Let me know if you need more.

[Cliff Fendley]

Red Cent, I remember something about the bobbin tension on mine, it would pull the bobbin thread up on thinner material and the bobbin tension was as tight as it would go. It worked fine with 277 bobbin thread but it had near zero tension on 207.

I remember calling Steve about it and I had to bend the spring to put more tension on the bobbin thread. I was then able to adjust the tension.

I don't remember ever adjusting the top tension.

Now that it is set I never mess with it.

It still tries to pull the bobbin thread to the top when sewing a single layer of thin material like making the turn on bullet loops on a money belt. I'm thinking about switching to a smaller needle for that thin stuff and see what happens.

[Massive]

Cliff, that just sounds like you need to lower the bobbin case tension, simplest way is to undo the screw say 30 degrees.  I mark the bobbin next to the screw with a fine sharpie line, so I can precisely reset it.  Another way would be to put 207 in your bobbin.  I prefer to do adjustments.  Another way is to adjust the top tension, both screws at the same time, 1/8 turn at a time.  With my Cobra the lower screw does not have much run in it.

However, as you reported Cliff about your cobra, my Techsew gb6-180-2 had a standard 7 type bobbin and it was not adjustable.  Partly I think the guy who owned it before me flattened the whole thing, out, by cranking the screw, but then, why would he do that?  I don't think it worked in the first place.  I could normally get it to work OK with sometimes by backing the screw off several full turns.  This kind of thing is why I try to have more than just luck on my side, I want a setting that I can set if something goes pearshaped.  I got myself into trouble with my sailmaking machine, and had a hell of time.  The reason is because I adjusted the lower tension.  And got it out of whack, and spent two years trying to figure it out.  

The problem with the lower bobbin is that it is not a well worked out system (on industrial sewing machines being sold to weekend warriors).  It works great if you really know it.  And it works great if your sewing allows you to never touch it, but it is not obvious for the guy who is in-between and needs to vary his set-up, and there aren't big knobs with markings on them, etc...

Another thing is that as nice as these new Asian machines are, that have been tweaked by legends and experts, the assemblies are not in the same world as a 20 dollar singer picked up off ebay.  The old cases were machined, the springs were like springs in a gun.  The hooks did not scar from a needles strike (problem with a different machine I own).

There are a lot of self-regulating aspects to lower bobbin tension.  Larger threads need more tension and they get clamped more by the spring.  When the loop is pulled up smaller loops have less resistance setting in the work, and larger loops have more.  So there are elements that are just plug and play.  But the machines also purport to run 69-450 thread (speaking of my GB6) and that is a huge range.

[Massive]

It still tries to pull the bobbin thread to the top when sewing a single layer of thin material like making the turn on bullet loops on a money belt. I'm thinking about switching to a smaller needle for that thin stuff and see what happens.

It is certainly worth a try.  My machines have almost all run better with the bigger needle in a range.  I think the reason for this is that in this kind of machine the tension is transmitted by the needle.   A lot of the fabric stuff I do is in sailcloth or coated nylon.  Guys are always suggesting smaller needles because it means a slightly lower chance of ripping out the seam, and on coated, smaller holes to seal.  But one, it causes all kinds of problems.  And two, I always figure that all the bad stuff it does is stuff pros would not put up with, so they are going to run a bigger needle.  On leather, the tension issues are way worse, and hand sewing uses awls which leave bigger holes, if sometimes nicer looking, holes.

Anyway, it is all a range thing, so your perfect range might be with a lighter needle.

[Red Cent]

The video tells us the bottom tension is adjusted by the upper tension screws. I have been though a wide range of adjustemnets and wound up with something that Massive describes. However, the bottom thread is almost a straight line. The upper stitch looks great. Tight and thread is buried in the stitch groove.
The "manual" speaks to a bobbin adjustment done in 1/4 turn increments. If I would start to tighten the bobbin tension, what should I expect to see using my present status?

[Cliff Fendley]

Massive, If I lower the bobbin tension wouldn't it let the top thread pull the bobbin thread up worse?

I know it seems backward but when sewing real thin material I've been using 277 bottom thread instead of 207. The heavier thread doesn't pull up through the hole and the thread is tighter.

Red Cent, I would think more bobbin tension would make your problem worse. It appears yours is opposite of mine

[Massive]

You are right, I got lost on that one.  If the lower thread is coming up, then you need to either raise tension in the bobbin, or lower it in the top, depending on whether the problem is occuring with high or low overall stitch tension.  And your comment on 277 is right, though I personally wouldn't go about it that way.

[Massive]

The video tells us the bottom tension is adjusted by the upper tension screws.

That won't happen, what will happen is that adjusting the upper tension will position the knots higher or lower in the material, but it will do so without your having control over overall stitch tension.  But that could work out fine if your bobbin tension is in range.  I will take my factory adjusted bobbin out and see if I can come up with a way of quantifying the tension that is currently there.

I have been though a wide range of adjustemnets and wound up with something that Massive describes. However, the bottom thread is almost a straight line.

If by straight line you mean the lower thread is not up into the leather, and all the "knots" are exposed on the underside, then you need either more tension on top; smaller thread on bottom (but only if that is also what you want); lower tension on the bottom, so the knots suck up.

If you had a factory adjusted bobbin case, and have not messed with it, and the machine always used to work, then you probably do not need to adjust the lower if you are running in spec (not size 16 needled and 90 thread, say).  But if you have moved everything all over the place, in an attempt to get the machine running, then you need to recalibrate the bobbin case tension, lower the top tension as low as practical.  Start sewing while adjusting upper tenion until your knots bury.

That is the starting point, low calibrated Bobbin case tension, and low top tension, then suck the knots up, then check for overall stitch tension to be sure it is neither overworking the leather, or not holding it firm enough.

The upper stitch looks great. Tight and thread is buried in the stitch groove.
The "manual" speaks to a bobbin adjustment done in 1/4 turn increments. If I would start to tighten the bobbin tension, what should I expect to see using my present status?

Your knots would suck up into the leather, and overall stitch tension would go down.  The knots going up is what you want, but where overall tension is correct, is up to you.  One way to tell would be if you can remember whether the top tension devices are screwed down about where they were when you unboxed the machine.  If you get the knots centred,  but the top tension screws are well cranked down from where you though they were when you originally got the machine, then you probably still have too much tension on.

[Boothill Bob]

Whats the weight of the cobra with stand? I'm about to buy one soon

[outrider]

Those of you that need mauals...you can also use the Artisan 4000 manual for some the parts and adjustments...I use it on my Ferdco Pro 2000...it basically covers most of the machines that are Juki 441 clones

[Red Cent]

325 lbs.

[Massive]

Henrik, on the one hand the whole transaction went through as promised, with the exception of some missing parts.  The shipping to Canada, though was exactly as promised and worked out with no surprises.

Yesterday I had a problem.  I tried to switch the single side foot to a double foot just to see how that would go, and I stripped out part of the needle bar.  This because the meat on the fitting is 99 thou fatter on the double foot, which meant that the screw did not get retention in the needle bar sufficient to resist stripping it out when I tightened it.  I'm a machinist so I know about tightening screws.  I guess I should measure the parts first.

I still haven't heard from Cobra about my missing parts from several emails a while back, so I guess I am going to have to try them again on this.

[Red Cent]

What parts, may I ask?

[Massive]

They were short the thread melter and a second motor.