A word about belt squeal

[wicketdreams]

In an overwhelming number of posts on here belt squeal has been attributed to a few things...I just want to chime in on my particular problem...

Bought the car used..had the squeal when I bought it...snapped a couple of altenator belts..followed everyones advice and changed the crank pulley..Turned out not to be my particular problem...

My problem turned out to be the original owner put a remanned Altenator and the pulley was bad..originaly thought the bearings was bad..took it to an alternator shop and after pulling the alternator the guy imeediately said it was the pulley..he charged me $10 bucks and pulled the pulley from the alt..and sandblasted..put everything back together..no more squeaky belt...

 

[Mr Peepers]

I'm trying to understand what about the pulley was making the belt squeal, and why sandblasting it helped. Was the surface where the belt would ride glazed over?

-Curious