The Color of a Driver
Here is the story of heat tempering a
driver even if it's near impossible to photograph the colors as they
First thing you want to do is harden tool steel. You do if you've heated and reforged and straightened and the usual work in restoring an old tool that has been abused like so many are.
This particular candidate had been snapped off and ground several times before I met it, leaving a stubby ugly tip. So heating it red and pounding it over an anvil many times until the shovel tip began to reappear was what it wanted. Heat and swat it whilst it's hot, then go again. A piece of steel this small cools off soooo quick. It's about the best I do to get in 2 or 3 good swings before it goes dull again. So I worked it down slow.
The handle slips had also been chipped and filled with some unidentifiable gunk and I couldn't even tell what kind of they were to start with. But this is the smallest size of all the known Perfect Handle drivers and marked from the great Boker cutlery company of Solingen. It's destined for a friend and the only one if it's kind I've ever personally seen.
Heat the work bright cherry red and hold it there a while. This is really self explanatory as you can't miss glowing cherry steel in most lights and you can read about it on around 822 other sites. Just hold the work directly in the flame and keep moving it up and down the shank longer then you probably wanted after it comes up bright, and you'll be fine. Don't worry about the top of the driver here, since it's going to be left soft and you don't need it hardened. A common propane torch will do for very small work but if you light up 2 of them and point the flames at each other making a vortex, it goes 4 times faster instead of just 2. The flame below is a whole lot larger than it shows in the pic. A flash washes out the appearance of flame altogether .
The trick here is the waiting. If you leave it in the heat too long it will begin to color on the outside leaving the inside too hard still, so you heat a little and wait, heat and wait and on like that.
It goes funny greasy looking pale yellow you can barely see at first, it's a really odd look but once you've seen it once you won't forget. Light golden straw yellow is next. This deepens to brown with purple spots. It won't color even unless you heat and wait and watch, then heat just a bit more in the areas that need it. The tip or thinnest parts will go like wildfire before you can quench it, if you let it. So keep away from the thin parts to start.
Don't get in a hurry! Little more heat and wait, let the heat soak into the metal through and through.
For a screwdriver what I want is a spring temper shaft with a harder tip, but not too hard. This is not a cutting tool where you stop the temper before it even shows. I like nice solid blue for the tool and brown with purple just for the tip.
It takes about 5 or 6 minutes tickling in and out of the heat and waiting for the color to come, did I mention don't even think of trying to rush it!!
When at last you have the color just the way you want it, dunk it. Water is fine here, it won't warp on you at this point.
After the quench, take some fine abrasive paper and sand off the color or at least enough of it so you can see the entire length in bright clear metal again.
I repeat the entire process 3 times in all to get the deep even temper. I know guys do it less, but three times through and you can count on it.
Here is what I want to see. Deep even blue spring temper right to the tip where it fades to purple with just a bit of brown spotting at the very tip.
Works for me