Introduction: Making a Kitchen Knife - Version 2
Runner Up in the
Knives and Blades Challenge
In a previous Instructable a made a kitchen knife from a Machete and while functionally it came out great, it had a few flaws cosmetically. This is my second attempt at a kitchen knife and this time the knife came out awesome, I did have to change the profile of the knife as I was not happy with the bevel after grinding. So I ended up with a slimmer profile in the final product.
What makes this knife unique is it has chisel grind, meaning it has only one side of the knife has a bevel. The back side of the knife is flat. This allows to make really thin cuts/slices in food. This knife is for a right hand person, but a knife can be made for a left handed person as well.
I will show the steps I did to make this knife from start to finish. Also check out the video as that give you a good idea what was done to make the knife.
The metal I used was from a commonly available machete and is a good source of high carbon metal. This knife does not require forging (hammering out the metal) but it does require heat treating. To shape the knife I am using a stock removal technique.
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Safety warning: Wear appropriate safety equipment: safety glasses, hearing protection and respirator.
Step 1: Tools and Material
- Machete or other source of flat high carbon steel (table saw blades are another source)
- Wood for handles, I used maple and bocote
I will try to list out the tools I used:
For making the blade
- Angle/Mini Grinder with a zip cut disc
- Belt Grinder (1x42" is what I used but other ones could be used)
- Grinding belts 40, 60,120, 220 grits
- Various Files
- Forge or heat source for heating treating
- Various grits of sand paper (wet, dry)
- Japanese Water-stones (1000 grit, 4000grit)
For making the handle
- Belt sander
- 5 minute epoxy
- Drill and drill bits
- Sheet sandpaper
For etching the blade
- 9v or other similar battery
- Alligator clip
- Paper towel
- Masking tape
Step 2: Video
Here is a video of the knife from start to finish.
Step 3: Making the Rough Knife Blank
First step is to design your knife, I traced an existing knife and used that as my stencil. Once I had a stencil I traced it to the metal, in this case it's a machete. This knife will have a hidden tang (part that goes into the handle).
Cutting out the knife blank is easy with a mini-grinder, this could be done with a hacksaw as well but it will take a while.
The outline of the knife was cleaned up on the belt grinder with a coarse belt 40 or 60 grit.
Step 5: Heat Treating
To minimize warping, I heat treated the blade before grinding. The reason for this is the stock is so thin that heat treating after grinding could result in a blade warping and takes extra effort to straighten. While it is certainly possible to heat treat afterwards, doing it before hand keeps having to do any straightening to a minimum. The disadvantage to this is it is harder on grinding belts.
To harden the blade I used a propane forge, the knife was brought up to a critical temperature and then quenched in a container of vegetable oil. The critical temperature is when the metal becomes non magnetic, you can test by trying to stick a magnet on the steel, if it doesn't stick the blade is ready to be quenched. I ended up just heating until red hot and quenching.
Testing to ensure the blade did harden can be accomplished by running the edge of a file over the blade, if the file skates over the metal then it is hardened. If the file scrapes and catches means the blade was not properly heat treated or the metal is not high carbon steel.
Now that the blade is hardened, it is too hard to be used for a kitchen knife. Most likely it will snap as the metal is very brittle at this point. You want to strike a balance between the knife being flexible enough for use but hard enough so it holds a sharp edge. To do this you need to temper the blade.
Tempering is heating the blade up to a temperature that will "soften" the metal so it is less brittle. I did this by using my kitchen oven and baking the knife for an hour at 350F-375F, checking with a thermometer as the oven thermometer can be inaccurate.
Step 6: Straightening
There was a slight warp in the blade near the handle so I straightened the knife by hammer it on a block of wood that had a concave ground into the wood. Gently tap the knife and work in small sections and it should straighten, remember to do this after annealing not after hardening or you run the chance of the knife cracking or snapping.
To make the wooden block for straightening, I used a mini-grinder with a flap disc to carve out a concave in a piece of wood.
Step 7: Grinding the Bevel
This is the trickiest part of the whole knife making process. I suggest watching the video to get a sense how it is done but I will do my best to explain it in text and pictures.
This knife will be ground with a single bevel on one side (flat on the backside), if grinding a double bevel the process is the same. This knife will be for a right hand user. The bevel is ground in in multiple steps, but in the end it looks like one even grind.
It is important to have a bucket of water to dip the knife while grinding to keep the knife cool, because the knife is being ground after heat treating, we don't want to over heat the blade and ruin the heat treating.
The bevel will be approximately 1/2", to grind a bevel that amount it is done in stages. A first grind is ground in (multiple passes) and then a second grind is put in, then a third, etc until the height of the bevel is achieved. Step up after each grind. A rough grit belt was used 40 or 60 grit. Grind with the edge upward, with lots of light so you can see what you are doing.
Even pressure is placed on the knife on each pass, don't stop in one spot to grind or you will end up with an uneven grind. Key is do all the heavy stock removal with the coarse grits.
After the rough grinds are done, they are all blended together with finer grits to make a nice even looking grind that makes it look like one big grind. From 40 or 60 grit for the major grinding, then to 120 to blend then finally 220 grit. You can use other grits if that is all you have access too, such as 180 or 320 for a finish grind.
Once I was happy with the bevel and it has been blended, the next step was to put a rough edge on the knife. The bevel was flat ground until an edge started forming on the blade, this is the primary edge. I didn't go crazy to try and put a super sharp edge, the Japanese waterstone will do that. At this point the knife should be shape enough to cut paper.
During this whole process I did not grind the flat backside of the knife.
This is the most important and hardest part of knife making in my opinion, grinding an even looking grind takes practice so it will take a few tries to get it right. Practice on some scrap steel first to get a feel for how a grinding belt works.
Step 8: Redesign of Knife
I was unhappy with my grind so I decided to cut off the bad grind and reuse the knife blank and make a smaller knife. The same process was followed for the grinding as before. In the picture you can see another knife blank for size comparison vs the smaller knife.
This second attempt with a smaller knife came out excellent.
Also I left the the millscale/fire scale from heat treating to protect the knife since this is not stainless steel. This is a protective layer that keeps the knife from rusting and looks cool.
Step 9: Sharpening
There are many videos out there on how to sharpen a knife with a Japanese waterstone. I will attempt to go over how I do it.
The stone I used was a combination 1000 grit and 4000 grit. I placed the stone on a cloth and whetted the stone. It's important to keep the stone wet so when sharpening the metal and stone grit is washed away.
First step was to put a secondary edge on the knife, the primary edge was ground in during grinding earlier.
- Angle the knife on the 1000 grit stone and move the knife back and forth (see pics and video), working each section of the knife.
- The flat side of the knife was flattened on the 1000 grit stone
A burr will start forming on the edge, knock this off with some cardboard by stropping.
Run the knife in long strokes across the blade (see pics and video), again knock off the burr off with some cardboard by stropping the blade on it.
- Test cut some paper, if it does not cut well, repeat steps 1 though 4.
- Repeat step 4 with the 4000 grit to get it super sharp.
Step 10: Making the Handle
The wooden handle was made from maple and bocote hardwoods. A piece of maple was glued and clamped to a small piece of bocote with epoxy. The size was around 5" x 1.5" x 1". A two holes were drilled so the tang of the knife could be inserted. The tang was heated to red hot with a blow torch and then burnt into the wood to ensure a good fit. Eventually the knife blade would be glued in place with epoxy.
The rough handle was then shaped and sanded on a belt grinder by hand and by just eyeing it, to make an austere but comfortable handle.
Once the handle was sanded, it was finished with some antique oil for protection.
At this point the knife blade can be glued into the handle with some epoxy.
Step 11: Etching a Logo - Optional
A knife isn't finished until the maker puts their mark on it. For this I used electric metal etching. There are lots of tutorials on how to do this but I cover it best I can here.
- 9v battery, I used a 12 volt lipo but just about any battery will work
- alligator clip
- paper towel
- salt water (dissolve some salt in water)
- stencil and masking tape
I masked of the area where I wanted the logo and then traced out a stencil with an exacto knife and removed the section of tape where I wanted the logo. The stencil was held in place with some spray glue.
For the electric metal etcher, you hook one piece of wire to the positive of the battery and then to the knife. Then using another piece of wire, hook that to the negative of the battery and the other end to the alligator clip. Put a piece of paper towel in the alligator clip and soak it in some salt water. Place the wet paper towel on the area you want to etch, in my case the stencil that was cut out. You will hear the water start bubbling, move the paper towel around the area, you can tell it is working if the paper towel turns brown.
Do this a few times and change the paper towel once it becomes completely brown. The more you do it the deeper the etch.
Remove the masking tape and wash the knife. You can clean up the etch, area with a scouring pad and water.
Step 12: Cutting Performance
This was done before etching as I wanted to make sure the knife worked well. The knife effortlessly cuts meat and the ultimate test was cutting tomatoes. Where this knife really excels is cutting thin vegetables and charcuterie slices because of the flat backside.
I always think back to the Seinfeld eps when Kramer says to Jerry "Look how thin that is, see that's all surface area. The taste has nowhere to hide."
Step 13: Finished Knife and Care of Knife
Here is the finished knife, I went a bit overboard with the pictures but it's hard photographing knives, especially the shiny parts of it.
I also made a gift box from some poster board for it as the knife is a Christmas gift.
This knife is made from high carbon steel and it will rust if not properly cared for. Do not let it soak in the sink, as that is bad for the wood and steel. After each use wash and wipe dry, that is all that is needed to care for it. Over time the part the bevel that is shiny will take on a nice gray patina like the rest of the knife and will be very maintenance free.
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