The Dangers of Salvaged Stock

On making a knife from mystery steel.

Some time ago, I picked up a salvaged leaf spring from a car. A few years later, I decided to make a piece of it into a knife. I didn't know the actual steel alloy, or how to treat it, so I knew this was going to be an experiment.

I chose a self-handled "blacksmith's knife", a little like the pre-Viking "Kvindens Kniv" ("Woman's Knife") of Beth Holmberg's pattern someone showed me in class at Adam's Forge. I like how the handle turned out, but I clearly need more practice with a grinder.

Blacksmith's knife, rough forged.

To make it, I cut a piece from the leaf spring with a hot chisel, about an inch and a half wide by the length I wanted the completed knife, about 9 or 10 inches. I drew out half the piece long and thin, tapering the end, and rounded it (square, octagon, round), for the handle. I left the handle straight while I shaped the blade portion, first shaping with the tip pointing down but no thinning of the blade. Once I began thinning the blade, the tip bent upwards to the shape in the first picture, almost a complete reversal of the shape it had had before. Once the blade was roughed to shape, I curled the tip of the handle tightly, then curved the "guard" portion, and put in the curves working back towards the blade.

Blacksmith's knife, partially ground.

With the handle and blade shaped, I used the grinder to shape the blade some more. The Adam's Forge grinder is a very nice KMG, but the belts are a hit-or-miss proposition (I later built my own grinder). Just for fun and experience, I decided to try for a hollow grind. It took me a while before I could even come close to grinding evenly, but I was able to see an improvement as I went along.

Blacksmith's knife, broken during heat treat.

Over the next few years, I would pick it up and do a little more, then put it away again. I was able to do a passable hollow grind (8" wheel) and polish the blade to a level I liked. However, with a cleaner surface, I was able to spot some long cold shuts in the top of the blade. I triple-normalized and quenched in canola oil, knowing the cold shuts would probably make the knife unsafe to use, but wanting to see what happened. While trying to straighten out a slight warp, I cracked the blade across the flat. The cold shut on the top extended visibly through at least half the blade.

Cold shut on the back of the broken blacksmith's knife.

So, I learned a good deal from this experiment. I know not to straighten a warp in the

way I did. I like the way the handle turned out, and will probably make another, but with

slightly different spacing. The grain size at the break was very nice, about like 600 grit

sandpaper, and the edge was hard enough for a file to skate, so the normalizing and

quenching went well. And it's a pretty good confirmation that used steel can have hidden

flaws.

Depth of the cold shut.