GP Drills

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Yankee Drills


Restoration Techniques


Heat Tempering a Driver by Scott Grandstaff

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Here is the story of heat tempering a driver even if it's near impossible to photograph the colors as they actually appear.

First thing you want to do is harden tool steel.  You do if you've heated and re-forged 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.

Harden First

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.

When you hit cherry red and have held it there for a minute or two, dunk it quick in a can of oil.  They say peanut oil is best but I use 10 wt light machine oil because that's what I keep around the shop for lubrication anyway and I don't do that much heat treat.  After the oil quench, the steel will be as hard as glass and just about as brittle.  Don't drop it!!!  I have shattered tools before!

Pick it back up in your "tongs" (any pair of pliers or vise grips) and go back to the heat.  Only this time you don't just shove it in there and wait.  You have to "tickle" it.  Leaving it on the thick parts a little longer and way less to none on the thin parts for a while.  You put it in for a little and pull it back just as fast. Wait a minute or so and see if color begins to develop.

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.

Learn how. Discover why. Build better.

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