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How to Build a Knife

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Step 3: Rough cutting the blade--the easy part

Now it's time for the really fun part. Here's what you're going to need:

A hacksaw or jeweler's saw and several blades
An angle grinder with a hard wheel and flap wheel
Files (if necessary)
A drill
A vise
Necessary protection (glasses, gloves, jacket if you don't like sparks)
And a steady hand

Step one: cut out your blade using a hacksaw or jeweler's saw. If you're using a thick piece of steel, go with the stiffer hacksaw. I recommend standard, medium-to-fine blades. If you're using a relatively thin piece of metal and you have a jeweler's saw, you can cut out a pretty close profile which will save you some grinding in the next step. I just cut out a rectangle around my basic shape--using a hard, steel-cutting wheel, you should be able to grind through the excess pretty quickly. See picture one, below.

Step two: slap that blank in a vise and start grinding. Use the hard wheel on your angle grinder to cut away excess metal from the profile of the blade. This should be pretty self-explanatory; you're just cutting out a shape. The different colors that appear along the edge are just products of low-level heat changes in the steel, and won't compromise its strength or finished look. Remember those colors, though, you'll be using them to your advantage later when you heat-treat the knife. See picture two below for an action shot, and three for the completely cut-out blade.

Step three: grinding the edge. Use the flap wheel (the one with flaps of coarse sandpaper) to gently and EVENLY grind a slope to the middle of the steel. Don't go past the center, because that will give your edge a dip--and you don't want that. Picture four is of the job at this step, half done. Grind the other edge the same way, until the edge becomes an edge. If you think you're starting to go too far, STOP! Be patient. This is possibly the most delicate step in rough-shaping the blade. Work the edge evenly, so that it's straight and consistent. See below, picture five, for the finished shape.

EDIT 6/28/10: You can also hollow grind the edge if you have a wheel, or a belt grinder with a wheel attachment. Go to this link (http://www.instructables.com/id/A-Simple-Hollow-Grinding-Jig/) to see a jig I made to make this easy.

Step four: drill rivet holes. Make sure you use a drill bit the same diameter as the rod or rivet you plan to use. They can go anywhere and be any number, so get creative. Sorry, I don't have a picture of this...if you can't figure it out, try making something simpler, like a birdhouse.
 
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LOL im going to make a birdhouse.
What type of coal forge did you use. Is it a DIY one.
how long did it take to cut with the hacksaw
purplewg4 years ago
Just curious if a lawn mower blade would make a good knife blade? I don't mean the china stuff blades but good old USA made heavy duty blades.
zukomarley4 years ago
this is very nice. well done.
qwertyman104 years ago
Wow. This is going to be useful. Ive wanted throwing knives for a while, but theyre too expensive to buy, and they get lost. Im going to have to learn how to do this. Nice instructable! 
Couldn't I cut out the blade with say, a Dremel tool?
ibuildstuff5 years ago
When you are grinding down your blank try not to overheat the blade and change the color as shown in the 3rd picture. It can change the tempering in the blade and make the ratio between "hard" and "tough" change, causing the blade to either snap easier or not hold an edge as well.
Basta (author)  ibuildstuff5 years ago
That might be an issue with a blade that is already heat-treated, but this steel blank is not. In the fifth step I harden and temper the blade, after which it would be iffy to machine-grind the blade. The friction heat increases the temper, softening the metal--though it would be impossible to make the blade MORE brittle without heating to orange and quenching...the hardening process.
apod13 Basta5 years ago
it would be a good idea to anneal the blade a few times before you harden the blade though, to release all stress from the milling process of the steel and anything like getting heated up while being grinded
sharpsword75 years ago
u rock !were did u get the idea to make a knife?
JKibs955 years ago
Electric mandolin NEEDS its own instructible
ndelurey5 years ago
If I could only use one, which would be better: an angle grinder or a bench grinder?
danoliveri5 years ago
for making the edge should i use a bench grinder or angle grinder?
danoliveri5 years ago
i dont own an angle grinder do i need one? if so were can i get one and how much are they?
laci376 years ago
The best tool to cut this type of steel is plate shears.
lilel6 years ago
Can I use a hacksaw to make a chakram you know like the one on the show XENA: WARRIOR PRINCESS if you dont know its a metal circle frisbee weapon.
is there a certain fin ness of hacksaws like with sand paper or sand