I have got mine new in 1958 and it has always been a dream machine but that screw did that to me once and I had to take it to my repair man to get it out for me. I was also at the time having trouble getting the settings for the cams right and he fixed that for me also. He told me if I ever had trouble with the screw again to spray it with WD40 and let it set for several hours and it should come loose. I haven't had anymore trouble with it so I don't know how well it works. Good look with the machine it is a wonderful machine.