Turn an Old Saw Blade Into a Kamagata
by JGJMatt in Workshop > Knives
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Turn an Old Saw Blade Into a Kamagata
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Hello fellow makers!
In this Instructable I would like to show you the process I used to make my very first knife using an old circular saw blade. I don't have any of the fancy equipment that knife makers usually use so this will be great for anyone that would like to get started on this hobby with the bare minimum of tools.
And if you are a knife maker I would greatly appreciate any tips and tricks that you can leave me in the comments below.
In my previous Instructable ( LAYERED PAPER COMPOSITE RINGS ) I used pages from old books with resin to create a composite that I then created some rings out of, during that build I realised just how tough the material was and thought it would make a great knife handle.
As I don't have a forge....and too cheap to buy new metal....I searched for some alternative sources and found a lot of people that used circular saw blades to make knives from, so I set off to my local metal recycling center where I was greeted by a pile of old saw blades.
Join me on my journey to learn how to make your own!..
What You Will Need:
To make this Instructable you will need the following:
- an Old 9 inch or bigger saw blade
- Material for your handle
Mine is leftovers from my previous > Instructable < but you could also use some wood.
- Epoxy glue
- Butane torch
- Brass rods
- Sanding paper
- Glass pane
- Polishing compound blocks
Optional:
- Epoxy resin
- Brass tube
- Vinyl sticker
For the laser a matte black works best.
- Laser module
- Sharpening stones
- Alligator clips
- Salt water
- 12V Battery or power supply
- Sponge/cotton swabs
*As an Amazon Associate I receive a small percentage from sales made through provided links at no cost to you, this helps fund future projects.
Design Your Knife:
Shallots, garlic, herbs, itty bitty diced onion and tomato… none can stand up to the small but mighty Kamagata. The flatness along the edge and its height makes it ideal for chopping, and its flat-out adorable size makes it easy to wield for cooks of all sizes.
I started by tracing the old saw blade onto a piece of printer paper, now that we have our size limit we can start to design our Kamagata. My design is 55mm high with a 90mm cutting edge and a 20mm thick tang.
Once you are happy with your design you can cut it out with some scissors and stick it onto the blade with some school glue. Now you can either trace around the design or like I did use some spray paint and spray over the design and then peel the paper off when it is dry.
Cutting Out Your Knife:
Now we need to cut out our design.
You can use a thin reinforced metal cutting disk or a scroll saw to cut out the knife just take care as a lot of the circular saw discs have carbide around the edge that will eat away your blade very quickly.
After I cut it out I used a thick grinding disk to smooth out all of the edges and also round the curves.
Getting Rid of the Rust:
Now we need to get rid of the rust that is on the surface of the blade.
First we will need to soak the knife in a vinegar bath before sanding.
Removing rust with vinegar:
- Submerge the rusted object in undiluted white vinegar.
- Allow the object to soak in the vinegar for at least 30 minutes. If you're dealing with a lot of rust, a longer soak will probably be necessary. If that's the case, start with a couple of hours. Then, check on your progress.
- Pull your object out of its vinegar bath, and use a brush to scrub off any remaining surface rust. An old toothbrush or nail brush works well for this.
- Rinse the object with water, and dry it thoroughly with soft, clean rags.
- Repeat the process if any rust remains.
Next we will use a coarse 150-180 grit sanding paper to knock back the imperfections on the metal, now you can take this as far as you want to but I liked the small imperfections and lines left from its previous life as a saw blade.
Now we will be establishing our cutting edge depending on what you have available this can be done with a belt sander, bench grinder, a coarse sharpening stone or like I did using the thick grinding disk again.
We will be refining our edge later on, for now we just want to remove the bulk of the excess metal to establish our edge.
Optional: Etching
To personalise my knife even further I decided to etch something on the one side of it.
I decided to go with a floral branch as it went well with the overall design of the knife and have included vectors for you to choose from.
To cut the sticker I used my 3D printer to which I added a 0.5 watt laser module (You can find out more on my Instructable), loaded the vector into LaserWeb and generated a gcode that the printer can then cut out of the vinyl.
Next I cleaned the blade using isopropyl alcohol/acetone and transferred the sticker onto the blade make sure that there is at least 5cm of excess sticker around your design so that you don't accidentally etch other parts of the blade.
Now connect the positive from either a 12v battery or a power supply to your blade using an alligator clip and then the negative goes to your sponge/cotton swab (I wrapped some copper wire around the top of my sponge to make it easier to connect the clip).
Dip your sponge/cotton swab into a strong saltwater solution and begin gently wiping it over your design, rinse the sponge regularly in the solution and continue until you have a nice deep etch.
Mine took about three minutes.
Rinse the blade with clean water and then remove the sticker to reveal your beautiful etch.
Optional: Making the Handle Pins
This is also an optional step but I think it's really worth it, otherwise you can substitute this with plain 4-6mm brass rods.
To make the pins I started with a 6mm brass tube from an old antennae, then I searched through my jewellery scraps to find some brass rods that will fit into the tube (this was a 1.5mm and 3.5mm wide piece).
I cut both the rods and tube to approximately 6cm, this is way more than I needed but I wanted to be sure there was enough just in case I mess up.
I then stuck the end of the brass tube into a blob of play-doh (something like blue tack will also work, you just want to keep it upright and create a seal so that the epoxy resin doesn't leak out) and mixed a small amount of epoxy resin according to the manufacturers instructions, you only need 1 to 2ml.
Pour the resin into the tube and insert the brass rods.
Wait for the resin to fully cure.
Hardening the Edge:
Now this is the part I know is not perfect but as I don't have access to anything like a forge or kiln I had to make do with my butane torch.
Hardening is a way of making the knife steel harder. By first heating the knife steel to between 1050 and 1090°C (1922 and 1994°F) and then quickly cooling (quenching) it, the knife steel will become much harder, but also more brittle.
I've scoured the internet to try and find the best way to harden the knife with my available resources and went with the Japanese edge hardening technique that hardens the cutting edge, but leave a portion of the spine unhardened.
Fill up a container big enough to fit your knife into with hot water and salt (about 2 tbs per litre) this will be your brine to quench the knife in.
Now we need to heat up the cutting edge of the knife to critical temperature, you can test this with a magnet as soon as it is no longer attracted to the magnet it has reached the correct temperature.
Once your edge reaches an even orange color you need to quickly quench it in the brine solution until it has cooled.
To check the temper take a file and lightly rub it across the surfaces of the blade. It should bite into the area that was unheated, but should skate off of the hardened parts.
Next we can temper the blade by putting it in a 180 degree Celsius oven for about an hour.
Sanding the Blade:
Now for the final sanding.
I started with 400 grit sanding paper wetted with soapy water to get rid of the most stubborn fire scale on the sides and moved up to 1500 grit for a nice even finish.
I then placed a piece of 400 grit sanding paper on a piece of glass (or if you have access to sharpening stones that would work much better) and started refining the cutting edge.
I continued with the 400 grit until I had an even sharp edge, when the knife is complete I will just give it a final sharpening with old super fine sharpening stone I have.
Prepare Your Handle:
We now need to make our handle.
First grab some 400 grit sanding paper and sand the surfaces of the paper composite that will be against the tang of the knife until they are dull then place the two pieces of paper composite on top of each other and taped them together tightly with painters tape.
Then marked and drilled two 6mm (the same diameter of your pins) in the tang of my knife, these should be close to the edges of your handle.
I placed the knife tang onto the taped up paper composite and drilled the same 6mm holes through the composite.
Remove the tape and check that your pins fit through the holes nice and snug and that everything lines up. Then you can go ahead and cut off two pins of about 20mm.
Attaching the Handle:
Now clean the tang and composite with some isopropyl alcohol to get rid of any oily residue apply a thin layer of 2 part epoxy glue to both the composite and the tang.
Press the two halves onto the knifes tang and align the holes.
Next smear some epoxy glue around the two pins and push them all the way into the handle.
Clamp the handle until the epoxy is fully cured.
I recommend using a slower curing epoxy glue as the one I used started hardening as I was busy clamping it.
Trim the Handle:
We're almost done!
After the epoxy glue has fully cured it's time to trim away the excess composite.
I started by cutting away most of it with a cutting disc, just be careful not to nick the metal. Then using a drum sander and sanding flap disc I slowly took off the remaining composite until I reached the edge of the metal.
Now I switched to piece of wetted 400 grit sanding paper wrapped around a rubber foam block to shape the handle and get rid of any rough edges.
Finally I went over the entire piece with some 1500 grit sanding paper before moving on to polishing.
Make It Shine:
We have reached the final step.
Time to get polishing, I attached a cloth polishing pad to my drill, applied some fine compound meant for plastics and started polishing the handle first.
After the handle has reached a smooth semi-gloss appearance we can apply some coarse compound and get to work on making the blade shine, then repeat with the fine compound on the metal.
Buff the entire piece with a clean soft cloth to get rid of any polish residue.
Because I found the paper composite behaves much like a hard wood I finished it off with a coat of food safe linseed oil on the handle and buffed away the excess later.
Enjoy!
We have reached the finish line.
Now all that's left to do is to give the knife a final sharpening and then enjoy all the compliments on your new masterpiece at your next dinner party!