I have my late mother's 403 A with all the attachments and cams, and looked forward to using it at our home-away-from-home in the mountains. It has only one bobbin and no manual. An online search indicated that it uses Class 66 bobbins. I bought a pack of 4 metal Class 66 bobbins, and though they look identical to the old one, the center hole is too small to fit on the bobbin winder. Is it just a fluke? Have they changed the specs on Class 66 since 1960? I'd appreciate any help.

If this chart is accurate

https://www.singersewinginfo.co.uk/bobbins

There would be differences between the 66 bobbin and the apollo bobbin it lists for the 403. I would look for some plastic bobbins and try those.

Thank you, JoeJr. It's worth a try. Still puzzled, though, since my mom never used plastic bobbins.

Your Mom's metal bobbins were likely "vintage" metal bobbins, which are not the same as new ones. You could look for old metal bobbins and try those also, I suspect they would work better than new ones.

I'm sure that's right, JoeJr. Mom sewed through the 1960's and 70's with that machine. I never saw a plastic bobbin until 1972, when I received a 758 Touch 'n Sew as a wedding gift. I no longer have the 758 (traded it in for a Bernina), and it looks as though the 403 has held its value better than 758--though I don't plan to sell it.

The clear plastic Class 66 bobbins I have bought from WalMart work in my 403A.

Problem solved! I had bought the new bobbins in a fabric shop while visiting out of town. Last week I went to my familiar LQS, and when I described the problem, the first question was, "Are they Singer brand?" I looked, and found that they were not, but were made by a well-known notions company. I bought a pack of Singer brand metal bobbins, tried them out yesterday, and THEY FIT on the bobbin winder!