Introduction: Marking Knife From File
When making marks on wood, nothing beats a marking knife when precision is important. This simple knife was made from an old worn out file with rudimentary tools. If you have ever wanted to make a knife but don't have conventional metal working tools, this project is for you.
Step 1: Tools and Materials
Step 2: Anneal File
In order to make the file workable, it needs to be annealed. This will make it less tough and easily shaped. To anneal the file, turn on the map gas torch and heat it until it loses its magnetism. I set up my torch in my Hot Pipe Wood Bending Jig. I screwed a magnet to a long stick to keep my hands far away from the hot temperatures. Let the file cool down on it's own. If you have some, placing the file in a pile of sand will help it cool down slowly.
Step 3: Trace Pattern
Download the attached template and trace it onto the file.
Step 4: Shape Knife
Clamp the file in a vice and shape it using a hacksaw or angle grinder. Once the rough shape is achieved, refine it using a strip sander.
Step 5: Grind Bevel
Cut a 30 degree angle on a piece of scrap wood and clamp it to the strip sander. This will act as a guide for the bevel of the knife. Slowly drag the blade of the knife over the guide until the blade is almost sharp. Do not sharpen it at this point. The bevel needs to be on the more aggressive side of the file. The other side will need to be ground flat to ensure a sharp blade.
Step 6: Flatten Knife
Using a flat piece of sandpaper, hand grind the blade flat.
Step 7: Drill Pin Holes
Mark pin hole locations in the knife blank with a center punch. Drill 1/4 in. holes in the tang of the knife. Be sure to clamp the blade in place. Do not hold it by hand.
Step 8: Drill Pin Holes in Scales
Using a brad point drill, mark the locations of the pins in the scales. Drill corresponding holes in the scales. With the pins in place, trace the tang on the inside of the scales. Remove the excess wood of the scales.
Step 9: Harden Blade
To harden the blade, it needs to be heated just past the point when it loses its ability to be attracted to a magnet. Once heated to this point, quench it in oil. I used canola oil as it doesn't smell bad compared to other oils used for hardening steel.
Step 10: Temper Blade
If the entire blade and tang were heat treated, remove the scale before tempering. Since only the blade portion of this knife was hardened, I skipped removing the scale at this time. Removing the scale will allow you to see the color of the blade after tempering. Heat the blade in an oven to 400 degrees F for an hour and a half to two hours. I used a toaster oven I have the the garage, but any oven will do. Once heated, turn the oven off and allow it to cool until you can handle it by hand. It should be a pale yellow color.
Step 11: Grind, Shine, and Sharpen
Once tempered, remove the scale from the blade. I used a set of whetstones to hone and sharpen the blade.
Step 12: Epoxy Handles
Wrap the blade in painters tape. This will do two things, mask off the portion of the blade that shouldn't get epoxy on it, and keep you from getting cut. Once wrapped, place the scales on the tang. Cut the painters tape along the edge of the scale. Remove the excess tape and apply ample amount of epoxy to the tang. Attach the scales and pins to the tang. Apply sufficient even pressure on the scales using spring clamps. Let dry.
Step 13: Shape Handle
Once the epoxy is dry, cut off the excess pins. Shape the handle until it feels comfortable in the hand. Once the handle is comfortable, sand with increasingly fine sandpaper.
Step 14: Finish Handle
I finished the handle with a beeswax conditioner.
Step 15: Admire Your Work
Once finished, admire your marking knife. No new tool is complete until it has a location in the shop. Make yourself a holder and attach it to your Tool Wall.
You have made something that will serve you well for years to come. Keep it sharp and get making!
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Hi, thanks for the nice instrution. I´ve got 2 Question:
1. at 780°C (1420°F) the Steel will be glowing. is that correct?
2. how long did it take to flatten the file on one side by hand?
Yes, the metal was glowing when I hardened and annealed it.
Using the strip sander it didn't take too long. Maybe about a half hour or so.
Hello. You initially heated the file before shaping it enough to lose its magnetic properties. You then re-heat it at a later step to again lose its magnetic properties. Did they come back when cooled? Please explain.
Yes, magnetism will return once cooled. Carbon steel loses its magnetic properties around 1420 degrees F which is around the temperature you need for annealing and hardening the steel.
This looks great, I may have to give it a go some time. I have a whole load of old files I inherited. Is the steel used for making files particularly well-suited to this, after the heat treatments you describe?
Yes, as it is usually hard, high carbon steel