Introduction: Cast a Blade!
When I was a kid my father used to make jewelry. I watched him make
amazing things and I could always count on him knowing how to do something that would help me with my projects.
One day I asked him to make me a fish necklace. I was surfing at the time and everyone was wearing something interesting. Dad pulled out some cuttlefish bone and asked me to draw what I wanted on it. I drew a fish and then watched him turn my picture into a 3d object. He used a fine tipped oxy acetylene torch to heat up a bar of silver and drop forge it into a mould.
The result was so beautiful! The fish had a timber-looking grain running throughout it and it was timeless because of the old-school feel. I never forgot that day and have always wanted to try it again. Well here we are! Time to forge a letter opener with a timeless feel. This knife may not be practical as a bush-bashing, hair-whittling kitchen knife, but as a work of art it will certainly have people asking how you created it. I hope you all enjoy and get the opportunity to try this at your own home.
Step 1: Why a Knife?
Knives are one of the oldest tools and remain one of the most useful. A beautiful blade is rarely thrown away because people recognize its usefulness and topical value. Knives carry history, stories and are recorded throughout history.
This instructable is a great way to learn knife-making with a softer material. You will have the opportunity to think about blade design, functionality and purpose. I even discovered that brazing rod, after being poured, takes well to being beaten with a hammer. You may want to pour some blades that you can put into your forge and have a go at black-smithing. You will also learn a bit about grinding a bevel on a blade and shaping a handle - or at least get to practice and learn along the way.
I will outline the basics to the best of my ability so that you can go on a journey of your own.
Step 2: What Is Cuttlebone?
Cuttlebone is part of the skeletal structure of the cuttlefish. The bone runs from the tail to the head of the cuttlefish and is situated just below the skin on the top of the cuttlefish.
These bones often wash up on beaches because they float, though really good specimens can often be hard to find. My father brought me some from a beach he walks often here in Australia. You can also buy these at pet stores because people use them for a calcium supplement for their birds to gnaw on. "Num num num"
Because the cuttlebone is comprised of rich calcium layers and air pockets, it makes an ideal mould for pouring moulten metal into. This is one of the oldest ways of casting objects and there are a good amount of artifacts found to support this. Cuttlebones also create a very unique look with every knife because, like fingerprints and snowflakes, there are no two alike.
Step 3: What You Will Need
Things you will need for this knife:
- Two large cuttlebones
- Some 3mm or 1/8th ply wood
- Coping saw or scroll saw
- Quick clamps
- Pipe cleaner
- Brazing rod (not containing lead)
- Map gas or propane torch
- Crucible tongs
- Old tin (large enough for crucible to sit in)
- Selection of files or a belt sander
- Various off-cuts of bone, timber, stone, compressed paper or leather for making the handle
- Wet and dry sandpaper, various grits
Step 4: Make a Prototype
Here you can design your own blade shape. Make it fairly simple with not too many sharp curves, as you want the hot metal to follow your pattern with ease.
Here I used some thin ply to cut out the shape I wanted. Don't get too hung up on your shape because you can sand it down the track and neaten it up.
Use a coping saw or scroll saw to cut out your shape.
Step 5: Cutting a Guard
The small letter opener will need a handle so I decided to cut a guard out and mold it into the blade.
I first marked out the width of the tang and the top of the guard on a piece of ply. Then I cut the center hole till it fitted nicely. You can then cut the whole guard out and sand it till it's nice and even in shape.
Step 6: Pressing Your Shape
With your pieces cut out, it's time to start pressing the shape into your cuttle. I held the cuttle and used both my thumbs to push the prototype into the cuttlebone. The prototype will stop when the crushed cuttle dust fills the hole you are pressing. To fix this, remove the piece and blow the dust away, then continue pressing.
Most people only press in one cuttle side and use the other just to cover it, but because I want a guard, I decided to make two halves to ensure the mold line falls close to the center of the blade.
Once the blade shape is pressed evenly into both sides, fit the guard and push that in also. It's important you have enough cuttlebone to insulate a pour like this. You do not want molten metal to burn through the sides and fall out.
Hot tip: The less dust in your mould, the better your pattern will come out. You can use a straw to blow your mould out if you don't have an air compressor.
Step 7: Prepping the Mould
With your shape pressed simply, cut a funnel in the top of your mould and flatten it off. With the prototype still inside the mould, drill a small hole and push some locator pins through. I used some fine wire.
Now open the mould, remove the prototype and put it back together with the locator pins.
To ensure my mould stayed tight, I used a quick clamp to press it tight while I twitched it off with some pipe cleaners. Prop your mould upright near where your forge will be.
Step 8: Gathering Materials for the Forge
I am using map gas because it burns hotter than propane.
As my medium I am using brazing rod because it melts pretty fast compared to a lot of other alloys. Be sure the stuff you buy does not contain lead. Breathing lead is not a good idea. I bought a carbon crucible off eBay for $20AUD and some stainless crucible tongs which make holding the crucible safe and a breeze.
Step 9: Notes on the Forge
Now it's time to burn it! Or melt it.
This is a super simple way of making a forge. Just poke a hole in the side of a tin can and you're done.
Notice I angled the torch slightly. This enables the flame to flow around the side of the crucible rather then hitting one side and heating one side only.
During the heating process I placed some little flat pieces of copper on top of the crucible to speed things up. Add your brazing rod bit by bit till it's all melted. Better to allow more than less.
When the metal is hot enough you will see the surface moving. You will also see some patchy bits. These are impurities you don't want. Bend a piece of wire like an "L" and ladle this out before pouring. It will stick to the wire.
The pour must be made swiftly and accurately. Try to fill that mould as fast as you can.
Special thanks: To user "Ironsmiter" for answering some of my mini forge questions and offering good advice.
Step 10: Cooling the Mould
After you pour, the mould needs a little time to cool down. I then poured water on the outside of the mould, followed by over the top. The cuttle will soak in a lot of water. After about 5 minutes you can open the two halves to reveal what you have created.
My metal cooled at the top before filling the tang connection and so didn't completely fill my shape. I was not really upset because solder is cool stuff to work with. I will show you how I got around this later.
Check out the blade!!!! Cool huh.
Step 11: Attaching a New Tang
To get me back on track, I used some 45% solder to solder a new tang on. Simply put some brazing flux on your two clean surfaces and heat it up red hot with your torch and push your brazing rod in.You can use a piece of metal or pour another mould as your tang.
Clean up the tang and shape it with your bench grinder or a file.
Step 12: Making Your Handle
Now is the really fun part.
Gather hard materials of your choice and cut a tang hole through them. Here I used green suede leather as a spacer material and sangelo timber and samber stag bone to finish my handle. You can use timber as your last piece if you don't have any antler laying around. Be creative and have fun with the design.
To cut my tang holes, I drill a hole and then use a coping saw or scroll saw to clean them out to the right size. They don't have to be super tight, but very close is good.
Step 13: Drilling Pin Hole
I then used a drill bit of the same diameter as the brazing rod to drill my pin hole through the last piece. Make sure to push all your pieces down hard while you drill this hole.
Sand the brazing rod with course wet and dry, to create a hold for the epoxy to grip onto. I also sharpen one end to help me find the tang hole.
Step 14: Glue Your Handle
Now it's time to glue all your pieces together. Mix up some 2 part epoxy. I use 24 hour araldite because it's so very strong.
Use a sacrificial brush or small piece of timber to place a thick layer of glue between each spacer or piece of timber/bone in your handle. Include a good layer between the guard and first spacer.
Before placing on the last piece, fill it with epoxy be sure there is no air in this piece. Follow this rule the whole way as you stack your pieces by making sure everything is full of epoxy. Push your pin through the tang and make sure it has plenty of epoxy on it.
Since araldite dries like glass, it's important to clean up any you don't want on the blade or guard. Use a rag and the solvent suggested on the epoxy that you choose to do this.
Step 15: Let It Dry
Now it's time to wait 24 hours. Don't be hasty to start work on this. Leave it longer and you will be rewarded later.
Step 16: Sanding Down the Handle
Now it's dry, it's time to cut off the excess pin material and begin shaping your handle.
I have included progress shots so you can see it come to life. First sand around the whole thing to get all the pieces close to level with each other.
Next flatten both sides of the handle and sand down to the guard.
Add some detail by sanding slight finger grooves and rounding the top to make the piece flow.
Use a rasp or dremel to roughly cut in this shape if you don't have a sander.
Step 17: Sharpening Bevels
There is a right way to be accurate while doing this, but for this knife I did not feel it was necessary. As this knife is for opening letters you want the edge angle to be fairly steep, allowing the knife to separate the paper.
Start by grinding the bevels in on a bench grinder, alternating sides and checking your edge as you go. You can see the result is quite rough. If you don't have a belt sander or bench sander, just use a file. You would be surprised how quick a file chews through metal.
Swap to a 320 grit belt or a fine file to smooth out any lines. You can see how this looks afterwards, a big improvement.
Step 18: Finishing Handle
To finish the handle nicely, use some 600 wet and dry paper to rub out all the imperfections. Remember what style of knife this is and don't be too fussy, the idea is to create an older-looking knife.
After you're happy, rub the handle down with bees wax or gun stock oil.
Step 19: Finishing the Blade
Now you want to remove some of the oxidization that is making the blade look a little too dirty. I used a wire brush wheel, but a hand-held wire brush works just as well. Wire wheels throw steel bristles like bullets and they will go through clothes, so always wear eye protection.
Once this is done give the blade a buff on the edge also. You can use a buffing wheel, fine wet and dry or a scotch belt as shown above. Be careful if you use a buffing wheel, they tend to suck things in and spit them out just as fast. Stand to the side while wearing safety glasses!!!
Step 20: Contemplate
Now you're done you can sit back and get excited about opening bills with your new opener.
Remember, working with hot metals and power tools is dangerous. Use common sense and wear protection. It takes 2 seconds to put on the right gear and could save your eye or a trip to the hospital.