hi, I have the same problem on my wheel - an older home made one, which is a beautiful spinner, except sometimes I can't keep the screw done up. As I have only used this wheel during our hot Australian summer, I am wondering if there is a bit of grease on the screw that loosens it when the weather is warmer. I have to give the wheel a thorough clean and replace the drive band, so that will be one of the things I check as well. Cheers, from a cold South Australia that is giving a very good impersonation of winter!