I have never in my life cracked or broken a lock plate while straightening it out, which is a common requirement for cast parts made from old locks. Now other parts of the lock - that's a different story, especially the neck of a cock or a sear arm for example. In those case cases, I do prefer to heat. But have never found the need to do so with a lock plate, whether from TRS or one of Chris Hirsch's parts or any of the parts I have from mystery makers. Again, though, I'm not trying to bend them into a pretzel or straighten out a 90 degree bend - never seen on THAT crooked!