Making a knife is a tardy, subtle, many-sided and toilsome procedure. Knife making takes some skills in metalwork, woodwork and designing, much endurance, carefulness and tranquility. You’ll need to take it easy and not hurry to make sure you’ll succeed. Fine projects take practice, and you might craft dozens of knives before making your excellent one.
Design the blade
The blade’s concept is the most crucial constituent of the knife’s design. It must feature the best possible combination of functional power and appearance.
First, you need to sketch your blade and handle shape on plotting paper, as close to the real size as possible. Thus, you will not have to alter the design after it has been transferred on the metal.
Then, you need to determine how the handle will be attached to the blade. The three popular solutions are: full tang, partial tang, and through-tang. The full tang has the same profile as the knife handle and is covered by two planes of wood (scales) on both sides. The partial tang is, probably, the hardest to make: this type of tang is a pivot that projects back from the blade and is fastened with the handle by rivets. The through-tang is almost the same as the partial tang, but the rod extends all over the handle and is secured by a nut or by peening at the butt.
Choosing materials and components
For a fine blade you’ll need a carbon steel. Stainless steel will not do, as it must be excessively tempered and generally does not make a superior blade.
Take a plate of carbon steel about 3/16 inch thick. Also, to craft your knife handle you’ll need such material as wood, bone, leather, cord, stone, or maybe even gold, gems, or mammoth ivory. Precious wood, such as ebony, will be great for a handsome knife. Pins or rivets and epoxy adhesive will be needed to affix the handle.
Trace the design onto your steel plate in permanent marker. You may at this point amend your design as needed to fit it to your demands.
Cutting the blade
You will need:
- jig saw or a skiver, with several blades
- angle grinder with a hard wheel and flap wheel
- polishing machine
At all times remember about protective gear (glasses, gloves, protective jacket).
First, cut out your blade using a jig saw or skiver. A stronger saw is required for thicker pieces of metal. For a relatively slim piece of steel you may use a skiver to cut out a really fine profile – this will spare you some time needed for grinding. You may just cut out a rough piece around your basic shape with a stiff wheel, to grind away the excess later.
Put on your protective gloves and glasses and start grinding. Use a 36- to 40-grit grinding belt to cut away excess metal from the blade profile. You may notice different colors of the metal appearing along the edge: these are just products of heat changes in the steel that will not detriment blade’s soundness or appearance.
Then start grinding the edge. Use the grinder to accurately and uniformly grind a slope to the middle of the blade. Watch out not to go past the center, in order not to create a dip. Grind the other edge the same way. Be careful, as this is perhaps the most sensitive step in crafting the blade. You have to work the edge in a smooth flowing manner to make it perfectly straight and consolidated.
Next, drill rivet holes. The drill bit you apply must be the same diameter as the rivet you’re going to use. Wooden scales are usually attached with two rivets.
Pre-finishing the blade
Before starting the heat-treating stage, you need to pre-finish the blade. You’ll need:
- Sandpaper, grits ranging from 60 to 240.
- Sanding block, or sanding wheel.
Start with a rougher sandpaper and apply successively finer grits until you reach about 240 grit. The most crucial advice at this point is you shouldn’t stint: you should remove even minor scratches at this stage to not let them degrade your blade later. Make sure you work each successive grit transversely to the direction you worked the previous one: if you sand longwise with one grit, then use your next grit to sand edgewise. Also, remember to work all the visible surfaces throughout your blade. Give particular consideration to the ricasso (the area where the blade meets the handle) and the edges of knife’s spine and handle. Never fear to overwork: it’s better to work some portion of the blade that will be concealed than to leave a visible portion unsanded.
Heat-treating the blade is perhaps the most technical part of the whole job. You can use a coal forge, a gas forge, an electrical furnace or an induction furnace.
Almost everyone knows that steel must be hardened. The iron-carbon alloy’s ability to acquire, upon certain thermal operations, a better hardness, resilience and durability depends on the carbon ratio: the bigger carbon content, the easier a steel will harden.
Heat treatment of steel comprises two types of operations: hardening and tempering.
- Hardening is thermal treatment involving re-crystallization of a steel after heating it to an above-critical temperature.
- Tempering is thermal treatment of steels/alloys carried out after hardening in order to diminish/relieve residual stresses in the metal. Tempering decreases hardness and brittleness.
Hardening involves a sufficient exposure of a steel to a critical temperature (around 1380 to 2000 °F). Afterwards, the steel is cooled down quickly (quenched) to prevent any phase changes from annulling. Heat temperatures and other details are individual for each particular steel. A hardened steel obtains an irregular structure – it is very hard but also brittle. Therefore, it requires another type of treatment – tempering.
Tempering is performed by heating the blade to a lower temperature, around 400 degrees. This procedure makes the knife more tough (less brittle), while still keeping a relative amount of strength.
At this stage you’ll need a hardening bath. Different types of steel require different methods of quenching – oil quench, water quench, air quench, etc. The principal requirement is that you should be able to immerse the blade in the bath completely. You will also need a magnet – to determine the proper hardening temperature at which level the steel becomes non-magnetic.
Make a fire in your furnace and heat the blade from the spine, so as not to damage the edge. Steel will burn off and turn into an unusable melt if overheated. Heat the steel to a medium-high orange color – it is when the metal becomes non-magnetic. You may bring a magnet near the blazing steel, and if it is not drawn, the steel is ready.
Then leave the metal cool slowly in the open air, two or three times. This is called annealing and is needed to relieve strains in the steel that might be left after the rolling and milling.
After you’ve annealed the metal, heat it again to the same temperature, but this time immerse it into the oil bath. Make sure to wear gloves, as there will be some fire. After getting out your knife you’ll see it smoking. Now that you’ve hardened the blade, next thing you want to do is tempering it, because it is too brittle at this point.
Check the information on tempering in your steel’s manual: choose a hardness from the sheet and proceed with a respective temperature. The higher the tempering temperature, the softer and more elastic the blade will be. You may recognize the temperature of about 400–450 degrees Fahrenheit by a brown or purplish color. Put the blade in the middle of your furnace and leave it for one hour. The blade is ready. All is left to do is a little of final finishing work.
Finishing the blade
The defects visible after heat-treating may include tarnishing or scale (the flocky matter on the metal resulting from quenching). You’ll need to remove that stuff with the same finishing process you did earlier, however this time using a higher grit. Start with the 220 grit and work through until you reach about 350 or 400. Then you may start polishing the blade. All is left to do is the final step – making the handle.
Get a grip on your knife
Choose your handle material, for example wood. The wooden scales will be attached with brass rivets and epoxy adhesive.
Cut your handle plates. This part will be different, if you’re making a partial tang or through-tang knife. With a through-tang, you’ll probably be drilling a hole through the handle longwise. With a partial-tang, you’ll need to cut the plates, carve a groove in each one and glue them back together. This project is full tang, so it has two scales on either side of the tang. Use a table saw or a chop saw.
First, file down and sand the edge of the wood in the ricasso area (because after it is fixed you won’t be able to shape it any longer). Burnish the edge by placing both scales back-to back in a vise and filing them together, to make sure that both plates are even. You shouldn’t cut the rest of the handle to shape in order to prevent error at this point.
Then mix your epoxy and apply it evenly on the back of one of the scales. Lay one of the scales onto the handle. Make sure you don’t spread too much epoxy on the blade – while a little overage can be easily removed, a lot of adhesive will be a problem. Put the blade and the plate in a padded vise and wait until the epoxy has set hard enough. Then drill through the holes in the blade and in the wood. Make sure you use the same diameter bit you used to drill the handle. Then repeat with the other plate: attach it to the handle, put it in the vise, and then drill through the holes to complete the rivet holes. Add jiggling moves when drilling to provide enough space for the rivets.
Scrape any epoxy off the blade with a sponge. You may use a razor blade near the scales. Then, put the handle back in the vise and let it dry overnight. It is better to tape the whole surface of the blade to prevent grazes.
When the adhesive has dried, use a jig saw or a file to cut the wood down to the handle. Use a finer file to burnish the handle to its final shape. Next, put the rivets in the holes, cut them so that they are about 1/8 inch above the wood, and peen the ends down with a ball-peen hammer. Then file the rivets down and sand the handle up to about 150 grit.
Using a polishing paste and a new polishing wheel, buff the handle wood. A couple of passes will make the wood shine with a nice semi-gloss. At this point remove the tape from the blade and prepare yourself for the sharpening.
Sharpening the edge
The minimum of information on sharpening is as follows. You’ll need a good sharpening stone, large and preferably double-sided. Also, sharpening oil (for example, mineral oil) and a sharpening steel will be required.