How to Build a Knife

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.

Comments

[curious youth]

LOL im going to make a birdhouse.

[purplewg]

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.

[Basta]

Never tried it myself but to my knowledge they're made from good tool steel. They should work fine.

[hifatpeople]

They are like really rally hard to cut (although i haven't really tried cutting any other metal before) wore out a bench grinder on the lawn mower blade and broke an angle grinder on it. I'd try a plasma cutter.

[MR.builderguy]

all it takes is $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$!!!!

[badideasrus]

you could try annealing the steal, since you're going to temper it latter...

just heat it up reall hot, cherry red? then bury it in sand or ash, or some insulator, then let it cool. this will make the metal soft.

[clemsonguy1125]

What type of coal forge did you use. Is it a DIY one.

[jcardenas4]

(removed by author or community request)

[shadow wave rider]

how long did it take to cut with the hacksaw

[Homeschooler360]

Couldn't I cut out the blade with say, a Dremel tool?

[MrMystery96]

dependingon the thickness of your blank, yes. however, if you intend to do so, I would recommend using a solid carbide bit.

[Basta]

Short answer, yes. Longer answer, I can't vouch for the type of steel you're using and its thickness, which will complicate things. Trial and error is king.

[zukomarley]

this is very nice. well done.

[qwertyman10]

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! 

[picklepie159]

http://knifethrowing.info/self_made_throwing_knives.html
http://knifethrowing.info/make_your_own_throwing_knife.html#pahl
 perfectly balanced
i had the same problem. stupid new york laws make throwing knives hard to ship and get.

[ibuildstuff]

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]

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]

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

[sharpsword7]

u rock !were did u get the idea to make a knife?

[danoliveri]

for making the edge should i use a bench grinder or angle grinder?

[Basta]

I think it would be easier to use an angle grinder or, even better, a belt grinder.

[sharpsword7]

for the drill can I use a drill press?

[KenMN2010]

Would a bench grinder still work for most of extra stuff untill you get down pretty close to the edge?

[slydark]

IN my experience a bench grinder doesnt work anywhere near as well as either a belt grinder or an angle grinder. In further experience I have noticed that a belt grinder with a wider belt (say 4" wide) doesnt work nearly as well as a thinner, longer one (say 2" wide) I have used a wide belt grinder, a thin belt grinder and an angle grinder to make the bevels (edges) and any and all of them will work acceptably well. If you plan on using a belt grinder, try to find a good aluminum oxide belt, instead of your standard sandpaper abrassive belts.

[JKibs95]

Electric mandolin NEEDS its own instructible

[ndelurey]

If I could only use one, which would be better: an angle grinder or a bench grinder?

[Nebraska G]

Go with Both and experiment!

[Country dude]

is there a certain fin ness of hacksaws like with sand paper or sand

[Basta]

There is--most common are the coarse, medium and fine types, measured in teeth per inch of blade. The fine one is something like thirty or thirty-two, which is really the only kind to use for tool steel. Also, invest in the bi-metal blades, they'll last twenty times longer and cut through steel almost like it's wood.

[slydark]

along with this question about the type of blade youre using I have a couple questions. first, is that a really beefy jewlers saw that youre using? or different type of hacksaw that I dont have?
Also, in the picture it appears that y dont youre using some kind of diamond cutting, or incredibly fine rounded blade, is that so? or is it just as you said above, a bi-metal blade?
thanks so much. this is a great instructable, Im a bit sad I didnt find this before I became wholly invested in forging knives, as this seems a bit quicker (even if you get to pound steel! =) )

[Country dude]

Thanks man

[danoliveri]

i dont own an angle grinder do i need one? if so were can i get one and how much are they?

[Basta]

You can get one at the hardware store for pretty cheap--the cheapest are about 20 bucks. I think mine was about 60 to 90, but I'm not sure, I got it as a gift. Think about quality when you buy. To answer your other question about the forge, there's a few ways you can do it. I have a real steel-pot forge but you can make a makeshift version from firebrick, cinder blocks/breeze blocks or concrete. The two important components of a forge's construction are its shape--you need to make a sheltered fire in either a deep pot or a covered cave--and its air supply. You can use a hair dryer or shop vac on the reverse setting. The air needs to be delivered to the heart of the fire either by pipes or by your arrangement of bricks.

[laci37]

The best tool to cut this type of steel is plate shears.

[Basta]

That may be true, but I'd take a five-dollar hacksaw blade over a two-hundred dollar bench shear. I wonder if a small thing like that would work, or if the tool steel would wreck it.

[laci37]

Yes, I speak easily with four old plate shears... My family have collected everything over 60 years or so.

[lilel]

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.

[Basta]

I assume you mean the hacksaw blade as the stock itself? Yes, but it would take some bending and a difficult hardening procedure.