Marking Knife From File




About: My name is Troy. I'm a Mechatronics graduate studying Mechanical Engineering. I like to make things and spend time outdoors (especially SCUBA diving). I am a Community Manager for Instructables.

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



  • Map Gas Torch
  • Magnet
  • Sharpie
  • Vise
  • Angle Grinder
  • Strip Sander
  • Sandpaper
  • Hammer
  • Center Punch
  • Drill
  • Canola Oil
  • Oven
  • Whetstone
  • Painters Tape
  • Spring Clamps
  • Bandsaw

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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17 Discussions


9 months ago

I'm happy with my shaping. Since I didn't anneal, I did the bulk of it with an angle grinder then finished with a belt sander. It won't be getting a wooden handle.
Now I need to find a good heart source and was thinking of setting up a charcoal forge (pretty sure there's an instructable out there). Do you folks think that would work for hardening and temporing?

2 replies

Reply 9 months ago

Hardenting, it should work great! I don't think you will be able to keep it at a low steady temperature for long enough to temper it however.


Reply 9 months ago

Yes good point. Well I suppose I can use the oven in the kitchen to temper. Thanks


Question 11 months ago on Step 6

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?

1 answer

Answer 10 months ago

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.


11 months ago

This is fantastic. The steps on hobby-shop annealment and hardening are worth the time just by themselves.


11 months ago

Neat marking knife. great aesthetics


11 months ago

Walnut is the best for knife handles...


Question 11 months ago on Step 9

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.

1 answer

Answer 11 months ago

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.


11 months ago

I have been hoarding old files for some time now. I pick them up at yard sales, etc. I've wanted to make a knife like this for some time, but I was not sure exactly what I was looking for in a knife, and your knife has given me some inspiration. I like the torch holder you have there, so now I have to make one tool to create another tool. Thanks for posting this up, I really like it.


11 months ago

Great Job. You have included some really good tips for knife making.


11 months ago

Nice work I really enjoy making marking knives! Where did you get your wetstones?

2 replies

Reply 11 months ago

These are the stones I purchased. I then popped them off the plastic stand and made my own holder for them.


Question 11 months ago on Step 15

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?

1 answer