Singer SS diagnostic question for you.
 

OK, I am working on a 1946 vintage Singer straight stitch, gear driven, rotary hook, vertical end loading machine.
{( I'm not going to mention the model # at this time, as I don't want to prejudice the issue. )}

At slow speeds the machine sews beautifully. Perfect top and bottom tension with any thread put on it.

However ~ = ~

At high speeds the top thread looses it perfect tension, and wants to occasionally loop and skip stitches under the fabric.


I know the needle is correct and is in properly, threaded properly, that the bobbin is wound and threaded properly and the tensions are correct. Otherwise it would not sew as good as it does at low speeds.

Nothing I have done to date has corrected this. I can improve it by cranking in more top tension, but that is not a cure. Something is not right.

Now the question: What is your theory as to why this machine is doing this?

Joe

You're sewing too fast! ;-)

I'm thinking there's something going on in the bobbin area.

not knowing the model and being kinda unfamiliar with the mid century stuff, my guess would be loose bobbin/case.

From a purely mechanical troubleshooting point of view... I would look to see what might flex under load. if it does at low speed, then high speed could be worse.

are the "skipped stitches predictable? in other words can you know that at x speed over y distance you will get z stitches dropped? if it is constant in any way that can help point to the source.

I would double check the timing. I've found some timing issues (skipped stitches especially) are more noticeable with SS machines at higher speeds.

Why is keeping the model # secret important???

Jim,
I wish that was it. This little thing doesn't sew very fast.

foufymaus,
I'm afraid of that too.

Steve,
Predictable in that it will happen, but not predictable when or where in the stitch.

Candace,

I haven't gotten to the timing yet. That was next on my list.

No secret about the model, I just didn't want to mention it until I had an answer or two. Sometimes when the model is known people get a preconceived notion, and I wanted some generic answers.

The machine is a 1946 vintage Feather Weight 221-1.

It's back ground is that it's owner bought it untested. Found it wouldn't sew and took it to person who was a Singer FW fan. This person took the bobbin hook drive off, disassembled it, and then told her it couldn't be fixed and that it would cost $250.00 for parts. She said no thanks.
I said I'd do my best.
The bobbin case base, the part the bobbin case mounts in, that's held stationary by the needle plate, was bent on the right side where the cross cuts are. That was putting it in bind which caused the machine to jam.
I stoned it down until it would fit and rotate freely in the rotary hook assembly and reassembled the hook drive to the machine.

The bobbin case had a broken latch on it. I found one of those and replaced it. The replacement latch wasn't exactly like the original and I had to fix that too. It now works.

I did take a look at the hook timing when I fist reassembled the machine. It is off just a bit. I was hoping it wouldn't be a problem, so I didn't retime it.

I will do that next.

Joe

I've spent a lot of time retiming 301's (which are basically the same thing in this instance). They can do a perfect stitch and piece great, but when I try to FMQ (fast and needs to be dead on) I would get skipping. Upon checking the timing, it would be off a bit. NOt enough to give me fits when sewing a seam and you would think everything was fine. But, fire it up and do FMQing and timing would be off just enough, that the hook wasn't catching the thread EVERY revolution. This FW's timing may be close but off just enough that high speeds catch the problem. If the bobbin assembly has been removed like you mentioned, I would suspect the timing as my #1 guess.

Candace,

Thanks. I will check and adjust it as needed. I'll report back what happens.

Joe

I am not a speedy sewer (love that word, but seems to be universally accepted nowadays), so speed is not a problem with any of my FWs. However, I did give one to a cousin of mine a couple of years ago (and I know that full-on speed is her only speed); and when I saw her recently I asked her about the FW I gave her. She loves it for piecing, but she had that look in her eyes telling me that it isn't fast enough to suit her. So, should I attempt to find out if she wants it fixed, or just let it go, and let her not be as happy with a FW as she should be?

Sorry, Jon about jumping in on your post, but I tend to forget something like this if I let it go and keep on reading. If I think I can help her fix her FW, I would like to, and when you all get all yours answers in a row, I could call her. I have tried several times to get her on the board here, and she has signed up, but I am sure she never reads it. She claims she doesn't have time.

Likely it doesn't need "fixing". Of course she may see a bit of an improvement if it's serviced. FW's are not the speediest machines and have small motors. They suit many people just fine, but there are those that need speed that FWs are just not built/engineered to provide. Some models are just this way...I think the same of my 319. I've serviced several and they're just on the slower end of the spectrum. Believe it or not, there are people that just don't love FW's. I'm one of them. They're very sweet but apples for apples, the 301 IMHO is a much more powerful, useful and flexible machine. And it's faster:>