If you put the thread through the check spring before the bar, it will bend the check spring under bar and possibly break. Notice the distance and shape of the check spring at https://www.quiltingboard.com/vintag...ml#post6137169 Also note this is a 15-80 not a 15-91 as they are threaded differently from each other. The image at the link is like the Federal!

Janey - Neat people never make the exciting discoveries I do.

Do you have a manual?
Does the thread go through and grab the metal wire tension? And then up into the silver arm with a hole in it?

[ATTACH=CONFIG]611567[/ATTACH][ATTACH=CONFIG]611568[/ATTACH]Correctly threaded Class 15 clone, in this case a Modern Age, made by Juki circa 1957

I have threaded it the way of Sewjourney's picture. When the lever with the hole in it comes down while sewing it is some how wrapping thread around the bar before the tension disc area.

I have noticed on mine if I sew too fast the thread will come up out of the first notch at the top, and get tangled. Someone else had placed a small washer up there held between the faceplate and the body of the machine. I’m not a very fast sewist so I haven’t tried the washer, but next time your acts up see if the thread is out of the notch. It’s figure A in the drawing in my last post.

The thread Must go over the bar (thread guard) before engaging the take-up spring. Here's what I see as a potential problem. The take-up spring in your first pic is limited in travel, and consequently tension. Notice how yours exits the tension assembly somewhere around 2:30 o'clock? The pic of the Juki built clone shows the take-up spring at about 4:00 o'clock. More travel means it will remove more slack from the thread.

Loosen the set screw for the tension assembly and spin it clockwise. It will only spin within the slot provided. If more is required you may have to do a little bending of the take-up spring, or check the correctness of the tension assembly. Those springs are fairly fragile and can bend easily if not threaded correctly.

BTW- Love the 41 Mercury in your avatar. Takes me back to my HS years. My nicest car was a 41 Merc coupe. Wish I still had it!

I had a similar problem of tangled thread -- the spool would twirl around several times with each stroke. I tried putting one of those crocheted "spool doilies" over the spindle under the spool and that created enough drag to keep the thread from unwinding too fast. Just a thought...
The featherweight shop sells them, but if you crochet, they are easy to make and there are lots of free patterns available for crocheted flowers.

I was hand cranking outside on a windy day and kept snapping thread at the take up arm. Turned the machine 90 degrees and fixed the problem.

Hemlock thank you for the complement on my 41 Mercury. It was a 20th year anniversary present to ourselves. We us to have a 67 Mustang coupe.

The compliment was from oldmanquilts, but I agree -- very cool! :thumbup: