http://cpc.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=FN00233http://cpc.farnell.com/jsp/endecaSea...sp?SKU=FN00233

Just ordered some of them myself to lock-up my drills - theyve got an allen key head, and as Grant said, they just go into the holes where the ball bearings were (youll probably need to tap an M5 thread in it first so the screw doesnt meet too much resistance when going in). The screws in the above link are short enough so that once theyre pressing on the clutch, the heads lie flush with the plastic casing. Helps a lot if youre using drill mounts that sit flat against the plastic casing