Do M3 or M4 set screws exist that have a smooth shaft/shoulder on the socket end, only threaded at other end?

Question

It would have a limited threaded section, and the smooth, socket side protrudes. I want to use the exposed part as a side-bearing surface, in a narrow channel where a regular cap screw head would be of too great a diameter. In that sense it would not serve the traditional purpose as a set screw, so it may have a different name. References appreciated.

Also, the smooth shoulder should be greater than (but not a lot greater) than the nominal diameter, so as to provide a stop for the threading.

Answer 1

Unless you have access to a lathe to trim existing screw parts you will not find exactly that.

If you use any standard set screw it will not have the bottom wider than the threaded shank. You might be able to get a thumb screw with a small head that will fit your channel and will not stick up too high with the threaded part on the bottom. You could try looking over a catalog like this one http://www.wclco.com/pdf/thread/WCLTF20.pdf to maybe get lucky because they seem to have some low head ones already available.

If you were going to pay for machine time then any job shop could do screws from rod stock to match your needs on a per hour basis. See if a local vocational school could do that cheaply. If you have the machinist skills see if a Voke school would give you an hour's time during lunch hour or right after school to make the parts yourself.

Answer 2

It is called a shoulder bolt. Check McMaster-Carr for common sizes.