How to make a simple ‘Sandwich’ Friction Folder.
By Ben Cardoso - Le Mans, France.

Here is my guide on how to make a simple friction folder with a sandwich building.

Please note - Knife making involves the use of tools that can cause some injury - please ensure your work area is clear of obstruction and you are confident using the tools described. Gloves, mask and protective glasses are essential. No liability can be taken for any accidents!

Required tools:
1 dremel / multi-tool with sand drum, polishing discs, paste, and cutting disk
1 file
1 hammer
Awl
1 hacksaw
1 drill (preferably a pillar drill) 2mm and 3mm. drill bit
Sand paper 40, 80, 120, 240, 400; 600.
1 heat source, (blowtorch or torch ) for use with heat treatment.
1 belt sander.

Materials:
1 file in good steel (older files are best - modern day case hardened files do not make good blades)
3 mm steel pins or mild steel nail.
1 roll pin of 2 mm
2 brass washer of 3 mm.
1 wood piece of 3-5 mm thick, 2 cm high and 2.5 times the size of the blade.
1 piece of wood of the blade thickness and half blade size long
1 L of cheap oil.

After a final sanding and shaping of the handle, a little boiled Linseed oil bath for 24-48 hour will help protect and seal the wood.

Before cutting the blade shape from the old file it first needs to be prepared. Anneal the file with the torch heating it to a red cherry or until it no longer attracts a magnet. Allow the steel to cool slowly.

The rough blade shape can be cut from the file with a hacksaw.

Drill the heel of the blade (where the roll pin will be located) with a 2mm hole. Keep the hole approx. 1 mm from the edge of the blade.

Drill the 3 mm hole for the pivot. This hole should be located about 1/3 of the way in from the blade edge.

To form the bevel, use a strong file to remove the majority of material switching to sandpaper wrapped around a flat item for finer finishing. The movement is ‘heel to the point and point to the heel’ Ensure you keep the bevels symmetrical.

To start the forming of the blade edge bevels, use a file to cut a small notch where the bottom of the cutting edge will be. (approx. 3mm above the pivot hole)

After shaping the blade, it will then need to be heat treated to make it a durable blade capable of holding a good edge. Heat the steel with the blow torch to around the austenisation temperature (just under ‘red cherry’ in colour) and let it to cool to the ambient temperature.
Repeat this process 3 times, on the third time, as soon as the steel is at a temperature where it no longer attracts a magnet, put the blade in the oil bath (pre-heated to 60°C ) To test the quality of heat treatment, try to edge with a file - if the file slips it is good - if the file bites then the steel is still soft and the heat treatment process needs to be repeated.

The final stage of the heat treating process. This can be done in a domestic oven. Wrap the blade in foil and ‘cook’ it at 200°C for one hour.

Preparation of the handle parts can now begin. First, mark the handle shape on your piece of wood which should be about 3-5 mm thick and a good quality hardwood.

Fix the piece on the workbench and cut with the saw. Be sure to keep some excess around your guide lines to allow for adjustment / errors.

After cutting out the two sides, a spacer should be cut to sit at the bottom of the handle. This spacer must be the same thickness as the blade.

Drill a 3 mm hole for the pivot. Be sure to position the hole carefully to ensure smooth opening and closing of the blade.
Then drill two 3mm holes spacer in place in order to have everything in line. Ensure the spacer and blade fit well together.

Finish the wood pieces to their final shape and test-assemble to check fit. Make any necessary adjustments at this stage.

Cut a groove in the back of the handle with a file for the roll pin to sit into when the blade is opened.
Ensure none of the pin itself protrudes over the edge of the handle.

To secure the two sides of the handles, assemble the knife and peen the pins over. This can be done using a ball-end hammer - lightly tap the pin until the end of the pin flattens out to form a rivet.

You now have your very own traditional friction folder knife.

Tutorial and images courtesy of Ben Cardoso

Reproduced here with thanks.