Introduction: Hardening and Tempering a Screw Driver (&softening)
If you can already file the tip of your screw driver to shape it probably isn't of a high enough quality of steel to be hardened and tempered it may just be they have missed out the heat treatment to save time and money so for the sake of a bit of gas and a few minutes of your time it may be improvable.
If you have a good quality silver steel or carbon steel screw driver (one you can't readily mark with a file) you've damaged or need to adjust the profile of heat treatment is a good alternative if you don't have a bench grinder
Step 1: Softening
Heat he tip of your screw driver until it is glowing bright red, with draw it slowly from the flame so it cools slowly. Set aside to finish cooling.
Do Not quench the mug of water is for emergencies and the later steps.
Step 2: Re Shape
Ffile the blade of your screw driver to it's new shape.
I needed a finer blade on a long shaft with a better grip for the clock I was working on.
Step 3: Harden
Re heat to glowing red and quench in cold water, the blade should still be bright red when it enters the water.
Step 4: Polish
Clean the blackened oxide layer off with emery cloth or wet and dry paper if the hardening has worked properly it should be difficult to actually mark the metal with just finger pressure and emery cloth. The whole tip of the blade needs to be bright. Double check it is hardened by seeing if a file works on it any more if you wish.
Step 5: Temper
heat below the head of the blade so the oxide colours flow towards the tip when the colour you require (search oxide colours guide to hardness for images) reaches the tip quench, (this has to be done quickly)
I was aiming for dark brown but got well into the blues about 20 to 40C too hot but it worked ok.
If I were a perfectionist I could have repeated harden polish temper until I got it right