Splitting a Shimano MF-TZ500-7
I have a MF -TZ500-7 with extreme wear on the 14 and 16 tooth sprockets. As I have a spare cassette, I thought I would swap these 2 over. I expected to be able to get the 2 off by unscrewing them but doesn't seem to move. Are they threaded or fixed ie not replaceable? I'm sure someone can enlighten me