Old mechanical sewing machines are a true gift: robust, nice, effective and useful. Refurbishing them is, however, not so easy. Screws, particulary, are most of them made following old norms or simply following no norms. This is the story of a Singer sewing machine screw.
I had some previous experience on refurbishing an old Kohler sewing machine that we received from a relative. The machine supporting hinges lack a set screw of an unknown thread type. Not an usual metric or UNF screw. Reading here ans there I finally deduced that it was a “Nähnorm 100” (see this table) screw, a screws norm used by some european sewing machine makers.
Some days ago a good friend of mine come with a Singer sewing machine he found in the trash. He spent some time to recover the machine and now it is fully operative. He bought an old electrical motor for the machine. However, an specific screw was needed to attach the motor bracket to the machine leg. Because of the previous experience I readily thought it should be an special screw. Some googling after it was clear that Singer designed its own screws. Some tables show a large list of usual screws used in Singer machines. After talking each other we deduced we are talking of Singer screw number 50632, with a diameter of 9/32 in and 20 tpi.
After some work on the lathe, a new screw was made following the specifications that fitted satisfactorily to the machine. Following you can see some pictures of the screw and the sewing machine.