Chris;

That ridge...

...will make it more difficult to remove the drum once released from the tapered axle, but it just doesn't have anything to do with dissassociating it from the axle to begin with...if those two surfaces have been intimately close, and under preload from the nut, the thermal cycling which occurs will serve to lock them together incredibly well...unless of course there is the slightest film of anti-seize between them...

Alex;

Use a BMF, HEAVY DUTY, puller to apply serious, and irresistable force and CONCENTRIC to the axle...anything else will fail or do damage...

This is a subject which comes up time and again...I hope you learn from this experience and reassemble with anti-seize when you're done in there...you'll be glad you did, next time! I bought, and currently use a medium duty puller, and with very little (if any!) sweat shed, because of the AS preprep!

...more reading here: http://www.intelab.com/swem/service%20notes.htm#Braking%20System

JohnMc;

I absolutely agree that heat is not really the answer (although in a pinch, if a BF Puller was not available, I'd consider George's heat and quench idea), but if properly applied (concentrically) the force which even a mombo puller imparts is not in the weak axis of the shaft...luckily?

Cheers