I don't think there should have been any sideways pressure on the screw, its all taken by the gearbox output shaft, so the screw should have been just squeezing the nut in the wheel on to the shaft. I'll double check its all square and true when I get to have a look at it it at the weekend. Is there any chance you could drop me a link for the longer LH screws please? I got this spare out of an old dead battery drill, but if I break this one too then I'm out of them.