How can I fix Mountfield Laser Omega 46 Lawnmower?

How do I remove a damaged Blade Boss from a mountfield laser Omega 46 cm push mower. Do I need a special tool, and how and where is the key installed to lock the blade boss to the drive shaft. The Key resembles a coin cut in half or a half moon. Engine is Briggs & Stratton Classic 450E Product Code MP890002 Engine No 95902 0222 01 9604 ?????? , last part of engine no is unreadable.
Yawnoc1702, August 2017


done
whats the size of the two holes that fits onto the boss?i know they sit proud by 5mm but dont have the dims of the pins

MOUNTFIELD OMEGA LASER, September 2019
the key is called a Woodruff (Google it) key. It fits into a semicircular bottomed slot on the drive shaft and sticks up, engaging in a slot in the boss which the blade is mounted on.

The blade mount should pull off but you may have a struggle.

Acp, August 2017
link Click here to see other fixes for Briggs & Stratton.