I use a method similar to what Peter described to draw back the tang. Actually, I don't harden the tangs any more, but I still often do this just to make sure there won't be any problems drilling.
Ignore the color of the blade. It has nothing to do with the operation I am performing here. That's the tempering color. After hardening and tempering, I roll a convex edge on all my blades and test them prior to doing the hand-rubbed finish and assembly of the knife. This one has been tested and is ready.
Anyway, my method differs slightly from Peter's. I hold the blade with my bare hand near the ricasso. This keeps me in tune with the temperature of blade and gives me complete control. I start heating at the back of the ricasso, and "paint" the tang with heat.
When the heat becomes uncomfortable on my thumb (maybe 120 degrees F. ?), I ease the blade into a bucket of water up to the ricasso until it feels cool again. The water forces the heat on up the tang. There is no way I am going to over heat the blade this way. This one is 1084 which was tempered at 400 degrees F. I would have to go well past that to screw up the blade, and I don't think any of us can hold onto a piece of steel that is 400 degrees F. or higher.
The key is to heat slowly and keep the flame moving. Don't let any part of the tang get red. On some steels such as O1 and 5160, you can actually create hard spots getting them too hot. I take the tang to a light blue, then allow it to cool. I sand off the oxide colors and repeat the operation two more times.
I have to make sure I get these things dead soft because I drill my holes after the handle is attached. When you are first starting out and getting a feel for this, you might want to drill a small test hole near the end of the tang to make sure you got it right. You should be able to drill all the way through without using any coolant or cutting fluid. There are few things as gut-wrenching as starting to drill the holes on an assembled knife, and hearing that drill bit start to go *S-C-R-E-E-E-C-H*.
