Lots of information and parts here: http://www.tandtrepair.com/600TandSstuff.html

The bobbin case doesn't move, it stays put. The bobbin turns as the thread gets picked up by the upper thread. There is a hook and race that comes around with the upper thread, that is the part that moves under the bobbin plate. The touch and sew models have a very clever bobbin set up, it is a bit unusual and unfortunately I don't have something close to a 626 near me to guide you. It's not difficult though, and it's easy to follow the pictures in the manual. The bobbin case should click secury into position and the bobbin should drop in snuggly. Do a youtube search on Touch and Sew in geneal, it will likely have identical bobbin area setup. There is a tiny setting lever near the bobbin not sure what to call it, it has a flat round top, it has to be in the right position for sewing.

I hope you have the manual, double check threading. Also double check that the needle is put in the correct way, flat side facing backwards and needle threads front to back. The 626 model is the last of the all steel geared machines, it's a very good model, and I hope you know you have a machine worth spending time and money on. There isn't a single model made today with all metal gears, it handles layers of heavy to fine fabrics and it stitches very fine. If there's anything it is a bit more noisy than the the most silent Singer models, but it can be improved with oils like Triflow and Finish Line Ceramic Wet lube. They are perfect for vintage sewing machines, with added teflon and nano ceramics which add a noticeable smoothness to the machinery.

Remember to oil all the points shown in the manual, if it hasn't been used in a while, you need to give it a drop or two of oilk every where, run it a bit and then repeat the following days. Triflow and Finish Line Ceramic Wet lube are ideal, but any good sewing machine oil will do. You have a really nice machine, I promise :- )

http://www.sewusa.com/Threading_Diagrams/Threading_Pages/Singer_Sewing_Machine_Threading/singer_626_threading_diagram.htm

For
the busted gears: where are they placed? I can't find a user or service
manual for this model on the web. I'm sure you will get it sorted out,
as I already said, this model is good enought to have serviced and
repaired professionally. With a bit of luck and effort a lot can be done
at home too :- )

Might be too late to comment, butcI had the same problem that the needle wouldn't pull thread up from the bobbin, and the bobbin doesn't spin. I was told there were broken gears. I opened it up and found PLASTIC gears, not metal. I replaced the broken gears. But it hasn't corrected the bobbin issue. Still doesn't spin. Time to admit it's beyond me & take it to a repair shop.

I'm also having this problem and tried to solve this at home. But, i can't fix it. I need a proper guide to solve this. Please help me anyone...

Melissaneece43@gmail.com

Some of the 626 have plastic gears, some have metal. I recently purchased one that has all metal gears.

11-14-21

There are various forms for so I machine repair and collectors on the Internet. Summer on Facebook (and I don’t know about those other than that they exist), there’s someone read it spelled it REDDIT, and there are a lot on IO.com.

I collect, use, hoard, resell sometimes, and am gaga Over vintage all metal sewing machines. The all metal ones just keep going and going and going and they are beautiful to so with and to listen to and to watch work. (I also have a few modern ones that do all nice fancy things quite well and some of them embroider.

If you need help finding links for the sewing machine forums let me know either message me or post here. (I don’t frequent a lot of the forums here much because I have some issues that keep me from contributing much so it may be better to PM me.)

I have a singer circa 1960s so I machine with plastic gears that runs really well but it doesn’t stitch because of a plastic gear that’s broken :-) I have not bothered fixing it. It’s sitting underneath a table somewhere. I have other things I have to attend to and it’s just not worth my time but some people have done this and have given me directions how to do it (years ago).

You can look on craigslist or Facebook marketplace for all metal so I machines that will do pretty much what you’re touching sodas but our less prone to breaking. The plastic gears are definitely a weak spot in those older singer machines circa mid 60s.

Please excuse typos.