I assume 1mm thick means the depth not the width of the head. It could be a countersunk screw.
Assuming you have enough room, try using a good pair of "Mole Grips" to get the screw started.
If all else fails, try tapping with a centre punch at a 60 degree tangent, and replacing the screw
by
ElectricalEngineer
- 16 December 2009