how to torque a/c clutch nut

Just replaced my a/c clutch and coil and now instead of squealing when the a/c is turned on, it squeals when turned off. I don't think I have the nut that holds the clutch correctly torqued becuase the clutch spins while trying to tighten it. I have tried to hold the clutch with a screwdriver wedged in between the three metal rivets? Any help? Thanks

Once again I am a moron. I put the shim in front of the clutch as opposed to behind it on the shaft. Problem fixed. Thanks again and hopefully my mistake helps someone else.