This is the "dog clutch". It unscrews anticlockwise. However, as it is connected to the gears in the box, you first need to immobilise the gears which is most easily done by clamping a screwdriver blade (or similar) in the mincer outlet. Alternatively, if you have already part disassembled the gearbox, jam the internal cogs with a screwdriver. Although it sounds daunting, the dog clutch undoes very easily and removal exposes the two additional bolts you need to get at.
Clive Richards, October 2015
