A semi-practical application: Making a whittling knife from a worn-out hacksaw blade
The finished knife Recorder/Paul Franz
Different stages of making a knife blade from old hacksaw blade, from right to left. Recorder/Paul Franz
Hammering the hot blade Recorder/Paul Franz
Chris Curtis inspects his work Recorder/Paul Franz
Fitting blade into wood carved handle Recorder/Paul Franz
Copper rivets attach blade to knife Recorder/Paul Franz
Chris Curtis puts an edge on his new knife using his great-grandfather's whetstone. Recorder/Paul Franz
There are some things that you just can’t buy and your only affordable option may be to make these things yourself.
Woodworking tools aren’t in this category. Almost any woodworking hand tool you require can be bought, so there aren’t many good reasons to make your own. In fact there’s only one: it’s cheaper. Good tools are expensive. The alternative is to make them yourself.
Making your own woodworking tools is cheap, fun and satisfying if you’re relatively well coordinated and careful. If not, it’s a character-building exercise in pain and disappointment. There really is no downside.
The project: a whittling knife from an old hacksaw blade.
You will need: A MAPP gas or propane torch, vice grips, a file, a mason jar full of water, a hammer, a bench vise, a drill, some scrap wood, a hacksaw, sandpaper, a sharpening stone, a used hacksaw blade and two nails or similar thin metal rods you can use as rivets.
Wear safety glasses and be prepared to extinguish any fires you might accidentally start.
Begin by snapping off a two-inch section of an old hacksaw blade, sanding away the paint if there’s any left. The blade should break easily, demonstrating the brittleness of hardened steel.
If you have a bench grinder, grind the teeth flat and shape the piece as illustrated. If not, heat the metal until it is almost red hot, slate gray and faintly glowing in poor light, then let it air cool. Repeat. It should now be soft enough to file the teeth flat and to shape without destroying your file.
Once that’s done, grip the metal at what will be the dull end, or tang, which you will eventually fit into the handle of the knife.
Heat as much of the piece as possible to red hot and nonmagnetic. You will only be hammering the last half-inch of the blade blank, in this case only the edge, but heating the whole piece will make it slower to cool while you work.
Hammering is the fun part. What you’re looking to do is create a bevel along one side, the straight edge.
Once it’s red hot, lay the metal flat on the anvil — not letting go of the tongs unless you want to flip a razor-blade size piece of red-hot metal into your face or onto your exquisitely inflammable house — and give the forward-facing edge a couple whacks with the hammer, then reheat and repeat, flipping the piece to hammer the other side of the edge as the metal will bend upward where it is struck and must be kept straight. You are only bevelling one side of the blade. Bevel the spine and you will end up with severely lacerated thumbs down the road. Don’t hammer the flat of the blade unless you need to thin it out. You need to thin it out if you are working with a scrap of auto suspension spring or a railroad spike — railroad spikes are lousy steel, don’t bother — there is no call to thin out a hacksaw blade. Don’t hammer the metal while it’s cool or it will crack — if not immediately then later, when it is quenched.
The goal is a thin, tapered edge, but not so thin that it crumples. Given that the material is already very thin to start with, the hammering portion of this project is almost exclusively for the fun of it.
Once you have achieved something that looks like a knife blade, let it cool for a couple of seconds until it is no longer red hot, then quench by dunking it quickly into the mason jar. At this stage, it should be soft enough to work with a file, so do any filing necessary to straighten the edge or flatten the spine of the blade. Next, reheat only the last inch — the tang needs to stay untempered in order to drill later — to red hot and nonmagnetic and quench immediately, tip first and vertically or the steel will warp. It may warp anyway.
Test the piece with a file. If a file skitters across the steel without removing material, you’ve done a good job. Given the short length of the blade, it is unlikely it will have warped while quenching. If everything checks out, proceed. If not, start over. It’s just scrap metal. For the crucial next step, sand the scaling — a rough oxidized layer — off the surface of the blade and wipe it clean with alcohol.
Now, with the torch flame turned as low as it will go, pass the flame steadily and repeatedly over the blade, keeping the fire along the spine and away from the thinner edge. You should see faint colors begin to spread from the spine to the blade.
Because this is a short blade it will not need to be exceptionally flexible, so a deep, golden yellow is the color you are looking for at the edge. With practice and luck, you can soften the spine of the blade to a flexible blue while leaving the edge hard yellow. The second you see the color reach the edge, quench the blade to arrest the process.
Now, find the scrap wood or a dowel and rough out a handle. Cut a slot the length of the tang into the end of the handle using a hacksaw, which is not normally meant for wood but is — not coincidentally — the same thickness as the new blade. Insert the tang snugly into the slot, drill two holes through the wood and the soft steel and secure with two nails fitting snugly into the holes. Use heavy-gauge copper wire instead if you’ve got it. Clip the nails or wire short and mushroom the ends with light hammer blows to rivet the blade in place.
Sharpen the blade with a whetstone, diamond stone or similar sharpening equipment and you are done.
This technique is useful for blades in uncommon shapes or sizes, for particularly fine details or for reaching unusual angles in small carvings. Thicker saw blades, such as those from reciprocating saws, may be substituted for the hacksaw blades if you have them lying around. Car springs are great, nails or horseshoes aren’t, but why not? These will require more hammering to produce a tapered edge, but the process is otherwise identical and there is a lot of room for refinement through trial and error.
— CHRIS CURTIS