Introduction: Pocket Knife From a File

The title of this Instructable can be a bit misleading. Technically speaking a pocket knife is a foldable knife that you can carry in your pockets. My instructable will lead you on your way to making a small fixed blade knife from an old file, small enough to fit in your pocket - a pocket knife.

Step 1: Find a Suitable File to Use

Step one is fairly simple, find an old file that you or nobody else will use again. Old rusty files are cheap and readily available from pawnshops and the dark corners of garages all over the world.

I believe most files will work for making small knives, but there are a couple of things to avoid:

  • Be careful of broken files as they could contain stress fractures that would be disastrous for your knife.
  • Don't just get the biggest and baddest file out there. You knife still needs to cut properly eventually, this cannot be done if your knife's proportions are completely off. (I am specifically referring to the thickness of the blade)
  • Do some research on the file you want to use. A quick search on google will probably produce countless knife forum entries on this subject. This is how you will determine if your knife has "good" steel. What you want is high carbon steel, this will enable you to harden the blade later.

Step 2: Design

  1. Determine how deep your pockets are. No, not in that way, physically measure them to know how big your knife can be to fit in there completely.
  2. Now that you have your file and the size of your pockets, you can start designing the blade.
    Draw a square the maximum size that blade can be, in my case, 13 X 2.5 cm. I started out with the idea of a butcher knife style blade, but added a curve to the leading edge to have a more effective,useful point. I used 3 of my fingers as the length of the handle.

Before you know it, you will have so many designs, it will be hard to choose which ones to make.

Step 3: Preparing the File for Use

Your file will be too hard to really work with in the way we want to at first. So unless you want to spend days grinding, you need to anneal it. Annealing is the process of heating metal to relieve the internal stresses (this will make it MUCH softer.

The easy way to achieve this is to build a fire, place your file in the fire and let it heat up. I let it stand on its edge and I try to have it heated evenly to prevent warping. When it is finally bright red-yellow, I move it to a cooler spot in the fire and just let it cool down with the fire.

When the file is finally cooled down, give it a quick cleaning with a steel brush and test an edge with a file (one that you have not destroyed in a fire). If the file is soft, the other file will easily bite into the softened metal.

Step 4: Cutting Out the Knife

This step can be done in many ways. How you do it doesn't matter, as long as you get it done.
I recommend drawing a spare of your chosen design on a piece of paper and stick it on the metal or just draw directly on the metal with a marker.

If you use an angle grinder like i did, secure the piece of metal in a vice or clamp and use the proper safety equipment. A hacksaw will work just as well.

Step 5: Final Shaping

If you have access to a belt grinder, big or small, I recommend using it to shape your blade. Again, a respirator and safety goggles are not a bad idea.

Don't get carried away on the grinder, it will remove material faster than you think. If you want a grippy back edge, stay away from it with the grinder and just leave the file's original teeth. For the smooth curves and tight edges, use files. A round file is especially handy for finger choils.

I recommend using a small round file to file in a groove where your knife bevel will begin - the plunge line. This will help the grinding process as well as show you where to start sharpening when the knife is finally finished. And i think it looks cool, you might not.

Step 6: Drilling Holes and Marking the Edge

Another simple but necessary step. decide where you want your knife's handle pins, mark and drill them. WD-40 or anything simple works well as cutting fluid. If you are unable to drill through the metal, it is probably still hard. If this is the case, just try annealing again.

I drilled two holes, one 3 mm for a solid stainless pin and a 6 mm hole for an aluminium tube.

Use a drill bit roughly the same thickness as your steel to mark the centre of your edge, you will grind to this line later. It will help you keep your grinds even and help you notice waves in the edge while you grind.

Step 7: The Rough Bevel

Grinding the main bevel is the hardest and longest step of making a knife. To get a bevel in your knife you have a couple of options:

Option 1: Using files

Using a flat file, simply start filing at an angle against the leading edge. Apply moderate pressure and just keep going at the same angle. This technique works well, but can be pretty slow and hard work. You are almost guaranteed a good, flat edge as long as you move evenly across the blade.
Making a quick, simple filing jig beforehand will simplify the process even more.

Option 2: Belt grinder

I use a large belt grinder, but a bench top one with a flat grinding surface is just as good.
Free hand or on a rest, the technique is the same. Hold the blade at a slight angle against the grinding wheel (or platen) , start at the groove we filed in earlier and drag the blade's face across the wheel slowly while applying moderate pressure. Try to keep your elbows locked in your sides and sway sideways to grind the whole blade. Pay attention to the whole edge, from the plunge line all the way to the tip.

While grinding quench the blade in water regularly, you'll know when (expect some blisters). I like to keep the sides even only a couple of passes on a side at a time, quench and turn around the blade.

If you are grinding on a wheel, let the wheel do the work. Do not try to lift the grind line by tilting the blade, just keep the angle you started with and the blade will hollow out and lift the grind line.

If you stay consistent and keep the edges even, everything will go smoothly. I start with a 36 grit belt until i have a solid edge and then swap over to a 80 grit as the main grinding belt. I grind the edge to about 2 mm before going to the 180 grit. This will clean the bevel before heat treating. Correct any grinding mistakes you have made, this includes skew grinding lines (check the photos above), deep gauges in the metal and waves in the edge. All these can be fixed my concentrating your grinding on one spot.

Option 3: Bench grinder

Using a bench grinder is the same as the belt sander/grinder. Just watch your fingers and be aware of where the metal is, you don't want your knife to pop up back at you.

Step 8: Heattreating

Before even thinking of heat treating, be sure you are happy with the shape of your blade, placement of the holes and your main grind. Be sure you cleaned up the deep scratches on the handle of your blade and in your edge.
Having a clean blade before heat treat will make much easier later.

Firstly, there are better ways of doing this, i know, but this method works just fine.

  1. Light a fire and get it really hot, use a blow dryer to get it hotter if needed.

  2. Place your blade in the fire, keep it as evenly heated as possible and let it get hot.
  3. When it is bright red, the metal should be above its eutectoid temperature. If the metal lost its magneticity, you are at the right temperature. Leave it at this temperature for a couple of minutes (called soaking). Watch the metal, it shouldn't get much hotter than this.
  4. From there you should quickly quench the blade, do not allow it to cool down, so keep your quench tank close to the fire. Before quenching, heat up the oil (i used normal cooking oil, the steel used in nicholson files are supposed to be quenched in olive oil). Heat a big nail or piece of metal with the knife and swirl it in the oil before you quench your blade.

    Grip your blade in the fire with tongs and quickly quench it in the quench tank (it can be anything that can handle the heat of your oil). "Slice" into the oil and don't move your blade side-to-side to prevent warping. let it cool and take it out.
  5. Your blade will now be very oily, burned and all round dirty. I usually wash mine with a bit of degreasing soap after a scrub with a wire brush to remove the scale. Spray the blade with WD-40 or another rust preventing oil.

Now the big moment...testing if the blade hardened. Take a file and run it across the edge, if it bites, your blade didn't harden. If it skimms across the edge, you are all good.

Your blade should be pretty hard now, too hard and brittle. You'll have to temper your blade.
Just pop it in the oven at about 200C, depending on the steel and let it sit for an hour, or longer depending on the size of your blade.

Step 9: Final Grinding

Out of tempering, your blade will be an odd colour, so start cleaning.

I usually go back to a 80 grit belt and grind down the bulk of my edge. The technique is exactly the same as before, but be careful not to mess up your grind when your blade is getting really thin.

Due to the lack of bulk in your blade, the edge will heat up quickly and without warning, quench as much as possible and do not burn the metal. Go slowly even if the blade is hard and the metal doesn't seem to be moving.

When your edge is nearing the 1 mm mark, i recommend switching to a higher grit belt (120-180). This is the last grit that will really remove metal. Even though this is a high grit, it can easily bite into your blade and cause you a lot of headaches and additional grinding. The higher grit will also heat up your blade faster.

I swap over to a 400 grit belt and quickly run up to a 600 and then 800 just to get the rougher grit's deep scratches out when i reach a thickness just more than 0.5 mm. These belts will only really polish

I wanted a smooth satin finish on the blade. Unfortunately this means hand sanding against the grind lines. I start at 800 grit and then go to 1000 and 1500. The idea is not to shine the blade, super fine scratches will give that smooth satin finish.

If you wanted a mirror finish, i would recommend starting at about 400 grit sandpaper and moving all the way up to 2000 grit. Be sure to remove ALL the scratches from the previous grit. Finish on a buffing wheel and fine buffing paste.

Step 10: Attaching the Handle

  1. Mark out a left and right hand side of wood for the handle and tape the two sides together.
  2. Start shaping the front edge of the handle scales, unless you are planning to use files to shape the handle. Do this to avoid the risk of clipping your blade with the sander later.
  3. Mark and drill your holes, scales still taped together. Be sure to drill them in the right place.
  4. Now rough up the insides of your scales in preparation for glueing your scales to your knife. No need to rough up the knife, it has a lot of file-grip. Rough up your pins too. I used stainless steel rod and an aluminium tube salvaged from a broken crossbow bolt. Tape your blade to protect it from the glue
  5. Mix your epoxy and be quick, glue your scales to your knife and tap your pins through. Be careful, especially with the tube, it will expand as you hammer which is what you want, but it can crack your wood.
  6. Clamp the scales onto the knife and leave it to dry properly.

Shaping the handle

When the knife is finally dried, you can start the shaping on your blade. I start with a rough grit on my belt sander as well as various files to remove the excess wood. I then round the handle scales on the slack of the belt.

Clamping it in a vice and using strips of abrasive on the back is also a good way to get shape in your handle. Just keep sanding, finish by hand sanding the scales smooth.

Step 11: Sharpening and Cleaning the Knife

Your knife is now almost finished, all it needs it some sharpening, a good cleaning and oil.


You should be able to use any sharpening system that is available to you, i just use my belt grinder. With the 180 grit belt hold the knife at an angle and drag the knife in a downwards motion across the face of the belt. Keep doing this for a couple of stroked on each side of the blade, remember: keep things even.

Keep on grinding till you notice a burr forming. This is your signal to swap to a finer grit - 400. You just need about 4 alternating passes and you should be good. Strop your blade on a piece of leather to line up the wire edge and it should be razor sharp.


Cleaning is very simple. I used a toothpick to scratch out all the excess epoxy and followed with some acetone on a couple of Q-tips. WD-40 was used to wipe the blade clean and i applied linseed oil on the handle scales to bring out the grain and protect the wood.

Step 12: A Quick Sheath

I am a complete novice at making sheaths, but i will run you through my process.

  1. Measure out the desired shape (square in my case, i want the knife to print like a wallet or a phone) and get a couple of pieces of leather. I get leather offcuts from the leather store.
  2. Use a thick piece of leather to provide structure as an innard for your sheath. Cut a hole in this piece of leather the size of or slightly bigger than your knife.
  3. Stick your three pieces of leather together- innard and two outside covers. I use a sticky yellow adhesive that is made by many manufacturers with different names. Clamp it and let it dry.
  4. Now i mark out where my holes will be for stitching. I don not have an awl, so i just use a very small drill bit and it works just fine.
  5. Using two needles and a waxed chord, start stitching. Push one needle through the first hole and pull half of your chord through. Now just push one of your needles through the next hole to the other side, do the same through the same hoe with the other needle and pull tight. You now have your first stitch, keep doing this all the way round the sheath. Tip: to avoid threading a needle through the chord of the other needle, slightly pull on the thread in the direction of the threading needle's motion as you are pushing it through the hole.
  6. With your sheath looking rough but stitched, test fit your knife.
  7. If it fits, cut off the excess leather from the sides of the sheath with a sharp knife. Sand down the rough edges either on a belt sander or by hand.

Step 13: Finally Done

I am pretty happy with the results of my knife. It is Small, sturdy and sharp. I tied a piece of leather through the tube for easy unsheathing. Best off all, completely legal to carry every day. Be sure to check out your local laws on carrying knives before you go out to show it off.

Keep your knife well maintained, sharpen it regularly (no need to go crazy). Spray it with some rust preventing oil (WD-40) and keep the wood nourished. Do this and your knife will be a good companion for many years.

Thanks for reading this Instructable, have fun building and experimenting with different shapes, sizes and steel!

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