I don't know that particular machine, but I wonder if it's possible that your needle is in the wrong position. It might be hitting the edge of the hole on the plate as it goes down. And when you're going slow it might bend slightly but still go through, but break when you're going fast because it doesn't have time to bend.

I would check this site: http://www.tandtrepair.com/600TandSstuff.html and do a complete inspection of the bobbin, bobbin case, and needle plate.

Bobbin case inserted incorrectly?

Feed dogs installed wrong?

Bits of broken needles and bent pins under the needle plate? Remove it and clean it out.

ALIGNMENT TEST:

Remove the bobbin holder, set the needle position to Center, the stitch to straight, and see if the needle moves smoothly up and down in the center of the hole. Repeat for left and right positions - it should miss the edges of the hole.

Make sure you aren't trying to sew with the needle at left or right positions and any sort of a zig-zag. It usually doesn't work.

WORST CASE: Someone ran the needle down into something so hard it bent the shaft that holds the needle. Unfixable.

Could be a timing issue too...

Thank you all! I did end up getting it to work without hitting anything-- the bobbin case was placed incorrectly-- but I realized now that the bobbin doesn't spin at all... I took it apart and oiled and cleaned it really well, and I found some gears inside with busted teeth. I am wondering if that is why the bobbin won't spin? Any ideas?

Thanks

take the machine to a repair shop. it has all steel parts and is a much better made machine than you can buy today. there are also places on line that sell parts for this machine. if you're really handy you may be able to repair yourself. c

I doubt if this machine is all steel. I believe it's a model from the 1960s and the gears are probably made of a type of plastic that has softened over the years, hence the breakage.. I'm not sure if it can be repaired, but I heard somewhere that they can be replaced with metal gears. If you have someone in your area that repairs old sewing machines, I would recommend calling them and getting their opinion. Sadly, I lost a beautiful Singer model 621 that had the same problem, because there was no one in the area where I lived at the time who repaired sewing machines, and I wasn't sure if it could be repaired. If you want a good,solid Singer machine, look for a 1950s model or earlier. I now have a Singer model 301A that I love - all metal, steel gears, no belt and sews great. If you want to learn about vintage sewing machines, go to quiltingboard.com and visit the Vintage Sewing Machine forum - tons of info, and great advice on buying, repair, etc. I have learned a lot about vintage sewing machines there !

I have an old touch and sew 740/760 series that is about 50 years old and I recently had the same problem. I think that my machine is just old and some of the parts are broken or frozen. As soon as we are free to move around again I plan to take my machine to a professional repair person. I have enjoyed the years of service.

Sounds like a timing issue. I had same problem with my Singer 626 Touch & Sew. The Singer 626 has mostly metal parts - but plastic gears. In my case, timing issue caused by the plastic gears wearing down. I purchased new gears (5) from Singer, and followed online videos about how to replace the gears and then adjust the timing.