by cheesehead » 15 Aug 2006 0:19
basically, you need to file a tiny portion of the shoulder and tip off. go slow, don't take too much off at once. you want the cuts of the bump key to make contact with the bottom pins, which will slightly push the key back due to the pressure from the springs. too big of a gap is bad, we're talking about, oh say, 1/16th of an inch or so. when you "bump" the key, it should cause the driver pins to "jump", thus opening up a gap at the sheer line to turn the key.