Hi Bookaray,
With all due respect to tbird, I must beg to differ with him. If you are referring to the radius at the end of the key, that radius should go downward into the female radius in the axle created by the round cutter that created the keyway to begin with. Look closely at your axle, and you will see the radius bottom of the cut. Match the radius on the key to the radius in the keyway. Happy Motoring!