How to Make a Knife Out of a Planer Blade

The high-carbon steel in an old-fashioned, handheld wood-planer blade is a good source of metal stock for making a tough, sharp knife.The planer blade has been specially hardened to resist wear and hold its sharpness. It will need to be softened before cutting a new blank to shape the knife from. The end result will be a versatile, medium-sized utility knife with a keen cutting edge.

Difficulty: Moderately Challenging

Instructions

Things You'll Need:

• Forge for heating metal stock
• Metal-cutting saw
• Oven
• Blade from a handheld wood planer
• Metal files: coarse, medium and fine
• Metal pans, 2, at least 8 inches long by 3 inches deep
• Metal tongs to handle stock
• Olive oil
• Water at room temperature
• Brass rivets, 2

How to Make a Knife Out of a Planer Blade

1. 
    
   Planer Blade

   Soften the blade by heating the entire piece until it turns bright cherry-red, then allow to cool very slowly (several hours) until it reaches room temperature. Use of a forge lined with firebricks that provide insulation during the heating and cooling stages is recommended.

2. 
    
   Cut Planer Blade to Shape

   Cut off a strip about an inch wide from one side of the planer blade, using a saw, such as a hacksaw, power jigsaw or bandsaw with a metal-cutting blade. Cut a piece off diagonally across one end to form a point at the tip. Use a file to round the corners where the cutting edge turns up toward the point.

3. 
    
   Honed Edge

   Hone the cutting edge to a thin wedge at an angle of 30 degrees, using metal files. Start with a coarse file and bevel the metal evenly, working from the side opposite the cutting edge. Use medium and fine metal files in succession as you approach the desired profile.

4. 
    
   Drilled Holes

   Drill two holes in the tang (the piece that fits into the handle) for riveting the finished blade to the handle. Select a drill that is the same diameter as the rivets you will use. The tang should be 1-1/2 inches long.

5. Harden the blade by heating it to a bright red-orange and quench in a metal pan filled with olive oil. Dip the blade edge first into the oil. Immerse the edge 1/4 inch and quickly withdraw from the oil. Repeat the process four times in rapid succession, dipping the blade an additional 1/4 inch each time until the blade is entirely submerged. Keep the blade submerged in the oil until it cools to room temperature.

6. After the blade has been hardened, it will become brittle. The tempering process that follows will change the crystalline structure of the metal to make it less prone to cracks or breakage. Clean off the oil with soapy water and a rag. Temper the blade by heating it in a temperature-controlled oven set to 400 degrees F for 20 minutes. (A kitchen oven or large toaster oven can be used for this purpose). When the heat cycle is complete, plunge the blade into a pan of water warmed to room temperature.

7. 
    
   handle

   Fashion a handle from a solid piece of hardwood. Cut a slot the same length and thickness as the tang. Measure the spacing of the rivet holes previously drilled into the tang, and drill holes in the hardwood handle to align exactly. Rivet the handle securely to the blade.

8. 
    
   Finished Utility Knife

   Poliish the sides of the blade with emery paper. Finish sharpening the utility blade with a whetstone or disc-array knife sharpener. Sandpaper the handle and finish with varnish or stain and sealer. Your utility knife is ready for work.

Tips & Warnings

• Firebricks used in a forge are made of a special type of ceramic. Never use clay bricks such as the common type made for constuction of houses or buildings--they can crack and even explode. Use proper precautions when cutting or filing metal, such as heavy workman's gloves and safety goggles. Make sure the metal is secured firmly in place while working by clamps, vise or adequate restraints. Use caution working with open flame and heating devices. Work in an envirionment free of flammable material with good ventilation. Have a fire extinquisher ready at all times.