Forging a San Mai Chopper from Welding Rods

Elijah of Fire Creek Forge uses one of the most ubiquitous welding rods available together with some 80CRV2 strong core steel to make a very cool large chopper knife using a San Mai layered forging technique.


00:00 Open the welding rod electrodes. Remove the flux form the arc welding rod electrodes to get down to bare steel. Hammering off the flux from the dry rods was the best approach.

0:54 Build a steel canister for the materials to keep the forge welding process atmosphere free to make the billet for the knife

1:12 use a drill and abrasive paper to remove the remainder of the flux from the arc welding rods

1:34 cut the cleaned rods to length to fit tightly in the canister. The inside of the canister is coated with white paint to prevent the contents from welding to the can, because the titanium dioxide of the white paint creates a thin non-welding barrier.

2:10 Add 1084 powdered steel for a strong contrast between the high carbon 1084 steel and the mild steel of the welding electrodes. Fill the canister and lightly knock with a hammer to eliminate voids

2:49 weld up the top of the canister. Leave a pin hole or drill a very small vent for expanding air to escape during the forge weld to prevent canister bursting. Heat the canister in the forge, and use the forge welding press to complete the process of building the billet.

3:25 free the solid chunk steel from the canister. Sometimes there is cracking on the corners but all the small steel rods improved the dispersion of tension so this billet appear nice and solid.

3:57 use the forge and flat dies on the forging press to form the steel billet into a flat bar.

4:10 Cut some grooves into the billet to introduce more patterning. Flatten the channels and draw the billet out longer and wider using the forge and forging press.

5:00 Cut the billet in half and clean up inside face of both halves to add high carbon steel in the middle. While the 1084 would make a decent blade edge, the abundance of mild steel from the welding rods requires more strength. Introduce the layer of 80CRV2 high carbon steel as a center layer to create a type of San Mai construction and provide the high carbon edge of the final knife. Forge weld the sandwich billet

6:22 After forge welding flatten and draw out the billet, address any delaminations, and cut an angle in the end to serve as the pre-form for the tip of the knife.

6:40 Begin drawing out the tang, and then draw the tip so that the central blade steel follows the geometry of the knife design. Use the forging press with the round dies to widen the work and modify to follow the blade design.

8:58 Begin narrowing the bevel so the San Mai or cladding is extended fully to the edge of the blade instead of revealing only about halfway up. The profile emerging from this final forming is like a classic Hudson Bay camp knife used by trappers for various camp chores.

9:46 Forging is complete. Normalize and begin the heat treating process, which are focused on the core steel which is 80CRV2. Complete annealing process

10:03 Cleanup the profile using the KMG-TX 2x72 belt grinder and its flat platen, and the small wheel attachment on the classic KMG.

11:00 Finish grind the blade with Beaumont KMG belt grinding equipment after a couple of tempering cycles. Pay attention to where the cladding is in relation to the 80CRV2 core steel. Clean and consistent forging together with balanced grinding will help keep that important middle layer centered. A ferric chloride dip early in the blade’s finish grinding will enable visual confirmation and help you make grinding adjustments as needed.

11:47 use the Beaumont rotary platen attachment on the KMG grinder for a supported slack grind to impart a consistent convex surface onto the knife.

12:04 Grind out the small inclusion using the 10 inch contact wheel on the KMG-TX. Inclusions run the risk of ferric chloride to seep into the blade during etching. Confirm shaving sharpness and then do a chop test

12:38 Edge deformation is visible after the chop test. If the heat treat is good, the next thing to look at is knife blade geometry. The knife edge may have been suitable for slicing action of kitchen cutlery, but was simply too thin for this more powerful chopper design. After re-profiling the edge on the KMG belt grinder, another shaving and chop test sequence confirmed re-profiling through grinding was successful.

13:44 Hand sand the blade, and then etch, and clean off the oxides about every 10 or 20 minutes. This mild steel etches differently than something like a nickel steel and required more etching to get the desired high contrast.

14:22 Install the olive drab canvas micarta handle and hand sand