Knifemaking: How To Build A Railroad Spike Jig

counter bending
counter bending

Building A Railroad Spike Jig Takes Time But Is Worth The Effort

Building the Railroad Spike Jig

Forged Knifemaking
This article is an excerpt from Forged: Making A Knife With Traditional Blacksmith Skills available at ShopBlade.com.

Counter-bending begins with the counter-bending jig. These are made by forging a steel bar .75-1 inch square and about five inches long into a “bottom swage” device. This looks something like a cradle. It can be placed into your anvil’s hardy hole or locked in a vise.

You don’t necessarily need to weld the hardy stud on the bottom, just lock it in the vise. A banana would fit nicely into this cradle. File a groove into the top-right edge to “catch” the point. I use railroad spikes to make this jig. As you make more knives you may choose to change that radius depending upon factors between you, your tools, and your steel.

Bending With The Railroad Spike Counter-Bending Jig

Place the counter-bending jig in the hardy hole or vise. Place the blade bar in the forge at the most convenient position for extraction and quick placement on the jig. Heat to orange.  Place the bar on its spine, with the choil and cutting edge looking up and the point at the groove. Keep the bar at the center of the jig.

Note the “air” between the billet and the spike. The blade is almost resting at the bottom of the jig. The next blow will force it completely into the concavity of the railroad spike jig.
Note the “air” between the billet and the spike. The blade is almost resting at the bottom of the jig. The next blow will force it completely into the concavity of the railroad spike jig.

NOTE: Blacksmiths will refer to shaping tools like this railroad spike jig as a swage. Sometimes as a bottom swage. Swages (sometimes called ‘swedges’) are concave in shape. Fullers, on the other hand, which are also shaping tools, are convex.

With the round hammer face strike the bar in the center. This will take one to several heats and hits depending on how hot the bar is and how hard you hit it. Rarely will it take one heat and one hit. Usually it takes many. Do not hit it any more than necessary. We want the entire blade in the concavity of the jig. When it’s there, stop.

NOTE: Remember that straightening blows are much lighter than forging blows. Straightening blows are just hard enough to bring the blade back to straight and flat.

Then, put the blade back into the forge, take a heat, and do the swage business again. Steel, when hot, is extremely malleable (like soft clay) and can be told what shape to take.

You can purchase Paul White’s Forged: Making a Knife With Traditional Blacksmith Skills here.

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