Hi, I tried to change over the cutting blades in my Ozito Rapid Shredder. The screws holding the blades down were very difficult to loosen. After several applications of WD40 and some brute force I managed to get one blade swapped over, but the other is stuck fast. The screws holding it seem to be siezed and the tool provided to unscrew them (a large hex key) has just stripped the hexagonal head of the screws. Can anyone suggest how I may be able to remove them ? Many thanks.