Learn how to remove the blade boss from a victa lawn mower.
Remove the engine from the lawn mower (click here for a tutorial). When looking at the blade boss you will notice on one side there is a hole, fill this with WD-40.
Place the boss over the anvil and hit it with a hammer, rotating the blade boss as you do so, this should loosen it and allow it to be removed.
This is by far the easiest method we know of, an alternative is to use two drawer pullers, however it will be difficult to find a pair small enough to fit.