Need Help, I'm stumped. Tension Problems - BIG time.
 

Well, it seems that something really went wrong with the Kenmore 120-491 I wrote about here:
http://www.quiltingboard.com/vintage...e-t189987.html

Some time after that post I had done some sewing and it sewed really good, not perfect, the tension at the longest stitch length was a little off, but nothing that made me worry.
Then I showed my wife how the feed dog dropper worked and since then it will not sew right.
The tension has gone on the fritz.

There was a place with icons on the top so one could put pics in order along with the text, I can't find it now. So I'm going to put the pics in as attachments.
Pic 1 is the top thread. You can see that at setting 7 it's OK, then as the settings were reduced the tension went limp.
Pic 2 is the bottom thread. Pretty much self explanatory. At the top tension setting of 4 it will not sew more than a few inches before the machine just jams up. Before it was sewing decently at that setting.
Pic 3 is the thread jams that occur on and around the bobbin at settings 4 and under.
Pic 4 is the top tension. I have not removed it or altered it in any way.
Pic 5 is a shot of the bobbin assembly and it's gate.
Pic 6 is the rotary hook and the inner bobbin carrier with it's two piece hook. The bobbin carrier cannot be removed from the rotary hook, the outer part spins around the inner carrier on the nylon rim you can see at the inner hook.

Now, here is what I have done:

>Read the owners manual and made positive sure everything is threaded and adjusted properly.
>Cleaned the machine thoroughly.
>Lubed it.
>From the time it sewed OK, till the when it went on the fritz the only things I did was show my wife how to disengage the feed dogs for FMQ. (and that was done as the instructions indicated) and replace the old bent needle.
The design of the feed dog drop system precludes anything getting out of alignment.
>Checked all the hooks, there are two on two separate parts, for burrs. Didn't find any.
>Checked the bobbin carrier and case at the top where the thread has bound up for burrs, did feel something on the case and polished it off. Made no difference.
>Adjusted the upper then the lower, then the upper alone, and then the lower alone tension to see if that is the problem. To make it sew I have to run the upper tension to 8. At this point you cannot pull the thread through the needle without it breaking. It is that tight.
>Watched carefully as I turned the machine through stitching cycles by hand. I can see where it's jamming up, see pic 3, but I cannot figure out why. Once past 4 there is enough upper tension to pull the thread around but not to stitch properly.
>Run the machine with out thread and needle to see what happens. At low speed the bobbin case just sits there. At high speed it vibrates in and out like crazy. But the tension problem is not influenced by machine speed. It happens at all speeds.
>I've read everything I can find about tension problems but nothing I've read covers this kind of malfunction.


This machine is not responding to the things that would normally fix a tension problem. It's my thoughts (my wife's too) that the problem is in the bobbin area. Instead of sliding around the bobbin carrier the thread is catching on it somewhere and it's taking a lot of upper tension just to pull the thread through.
You can see some of this area in Pic 6.

I need some help with this one. More to read maybe, I can't seem to find anything that helps with this problem.

TIA

Joe

Tammy,

Possible. But I don't see any needle marks on the bobbin case, and I can't remove the carrier to inspect it. I'll have a good look with a magnifying hood and see what I can find.

Joe

My bet is that when you dropped the dogs you got some rubbish or thread trapped in there that you can't see and the top thread is snagging on it. Try pulling up the bobbin thread as if you are just starting to sew, and see if you pull anything up with it. If you don't, pull the bobbin thread down underneath again, and pull it up again with the top thread. Sounds monotonous, but this is what I did time and time again last week on a machine because this was the only way I could clear compacted rubbish out from underneath because it was out of sight and out of reach. I pulled up enough fluff to weave a carpet.

Using a magnifying hood I did find some needle tracks on the bobbin carrier and rotary hook. Not sure how these happened, but they are there. I'll polish them with a ceramic stone in a bit.

Muv,
Will do. Since this thing can't be disassembled, at least I can't see how, if it can, your method might just get the job done.

Joe

I used to work at a sewing shop and to help get the lint out of the feed dogs, we would apply just the slightest amount of machine oil to the working mechanism of the feed dogs and then feed the thread through, the oil would make the lint stick together and was much easier to clean out. This will also pull up any tiny pieces of broken threads. But remember just a smidge of oil. When finished wipe away any excess.

Very strange bobbin case "system". Tough to fix things that arn't familiar. All I can think of is turn by hand and watch for exactly what causes the tangle. Looks like both your tensions are somehow getting messed up. How is the "bobbin case" tensioned?

jon

If if was sewing great until FMQing and a bent needle, I suspect your bent needle is the culprit. It hit something it shouldn't have. I've had machines go out of time simply for that reason. I'd check the timing. Also, be sure you have a correct needle in, in the correct way. If you've only changed needles, that could also be the culprit.

Jon,

Look at Pic 3. The bobbin tension is adjusted by the little screw in the center of the bobbin case. Very much like the early Kenmores.

Candace,
We never did get any FMQing done. I just showed my wife how it would be done.
The needle was bent when I got the machine. It's bent side to side and front to back ever so slightly.
There are no replacement needles available. The owners manual calls for a Kenmore #49 needle. The Boye #2 1/2 was another match and both of those are extinct.
The Overlock needle DCx1F is the closest match available now that I can find. It's a bit short so you have to seat it shallow to get the correct length.

I've used the new needle and the old needle and there is no difference in the problems.

I'll give the timing a look.

Joe

Joe, disassemble and clean out the upper tension unit, then reinstall it. Something doesn't look right in the photo of it: The piece on the right ought to be parallel with the piece on the left, yet the piece on the right is clearly canted at an unnatural angle.