Horn is a tricky handle material to work with. Horn is nothing more then compressed hair, and it displays many of the characteristics of hair...get it too hot and it burns, it wants to "curl" with humidity, and it can come in all types....fine, coarse, etc. Each time you work with horn material, it's a new game....it never works or acts the same way twice. One major recommendation I would make is to work it slowly, and do not let it get hot. I have literally watch a sheep horn scale "curl up" while it was sitting on the bench after grinding!
Some folks will boil and flatten sheep horn in hopes of getting more handle material from a horn...I would discourage doing so. I once boiled and flatten some Dall Sheep horn that was going on a knife bound for Florida. I used Loveless bolts, finished out the knife and sent it off to it's new home. About 2 months later I got a phone call from the new owner, telling me that the sheep horn was "pulling away from the tang". My first though was a small gap that could be heated, repressed, and glued back down. NOT! When the knife arrived, the rear half of the sheep horn scale was nearly curled into a "U" shape, and had pulled through the Loveless bolt!:what!::what!:
After looking at the knife for a couple of days, trying to figure out where I'd gone wrong, I realized that I had sent a sheep horn handled knife from Montana (15-25% humidity) to Florida (90+% humidity most of the time). After speaking with the owner a few times, we finally settled on me replacing the sheep horn with micarta, and refunding a portion of the knife's cost to the Client.
Just about any horn handle material is going to "move" more than you ever think it will. I still use it, but never will I boil it again, and I am very picky about using it, depending on where the knife's new home is going to be. I learned an expensive lesson with that knife, and don't want to repeat the mistake.