Most of the damage to the ward in the bottom of the keyway can be prevented by placing a piece of wire made from a large paperclip (make sure you leave a handle on your wire so you can't lose it into the keyway) in the bottom ward groove. Then your torque wrench is pressing on the wire instead of crushing the ward. It is common to use too much pressure when you're new. This will help you save your keyways. Here are a couple of pics of what I'm talking about:
A pic of the wire (sorry it's a bad pic, but it's just wire

):
http://i53.photobucket.com/albums/g47/p ... 8/wire.jpg
and a pic of it in the keyway:
http://i53.photobucket.com/albums/g47/p ... inlock.jpg
I used this until I learned to apply tension correctly, and still do on locks with soft plugs.