Most of the blades are too hard to bore through. I have ruined some expensive bits trying it. You have to remove the temper in order to do that. You can use a small map torch to remove the temper. To heat treat, I lay them on one of the large burners on the kitchen stove and turn it on high. The burner is not hot enough by itself, so I use the torch while they are on the burner to get them red. Once they turn red, I touch a magnet to them. If the magnet sticks, they are not ready, but if it does not stick, I know that i have the temperature around 1500. I try to hold the temp for about a minute to ensure an even heat treat. Then I quench in regular cooking oil that is about 135 degrees for 1 minutes, wipe them down and throw them in the oven on a cookie sheet at 500 - 550 for one hour. Oh yeah, cover the cookie sheet with aluminum foil before you start so you don't leave arrowhead shaped spots on it.