I don't know anything first hand about 301's, but I do know the 319 and 306 had an odd "bit" extra thing in the needle clamp that definitely has to go in the correct way, and can be very fussy to get just right, but those models have a set screw as well as the thumb screw..... I know there are a TON of 301 users out there though that should be able to say for certain.