How to Build a Knife

Step 3Rough cutting the blade--the easy part

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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25 comments
Aug 12, 2011. 5:14 AMcurious youth says:
LOL im going to make a birdhouse.
Jun 3, 2010. 7:30 AMpurplewg says:
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.
Oct 10, 2010. 5:23 PMhifatpeople says:
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.
Aug 5, 2011. 10:02 PMMR.builderguy says:
all it takes is $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$!!!!
Oct 22, 2010. 4:13 PMbadideasrus says:
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.
Jul 3, 2011. 4:39 PMclemsonguy1125 says:
What type of coal forge did you use. Is it a DIY one.
Jun 22, 2011. 12:46 PMjcardenas4 says:
(removed by author or community request)
Jun 20, 2011. 12:22 AMshadow wave rider says:
how long did it take to cut with the hacksaw
Sep 15, 2009. 8:43 AMHomeschooler360 says:
Couldn't I cut out the blade with say, a Dremel tool?
Dec 31, 2009. 10:22 PMMrMystery96 says:
dependingon the thickness of your blank, yes. however, if you intend to do so, I would recommend using a solid carbide bit.
Dec 31, 2009. 2:08 PMzukomarley says:
this is very nice. well done.
Dec 8, 2009. 5:53 PMqwertyman10 says:
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! 
Dec 27, 2009. 7:13 PMpicklepie159 says:
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.
Jun 24, 2009. 5:20 PMibuildstuff says:
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.
Jun 28, 2009. 5:29 PMapod13 says:
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
May 23, 2009. 4:45 PMsharpsword7 says:
u rock !were did u get the idea to make a knife?
Sep 6, 2008. 1:23 PMdanoliveri says:
for making the edge should i use a bench grinder or angle grinder?
May 23, 2009. 8:17 AMsharpsword7 says:
for the drill can I use a drill press?
Oct 12, 2008. 3:31 PMKenMN2010 says:
Would a bench grinder still work for most of extra stuff untill you get down pretty close to the edge?
Feb 7, 2009. 9:08 AMslydark says:
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.
May 19, 2009. 3:53 PMJKibs95 says:
Electric mandolin NEEDS its own instructible
Mar 17, 2009. 4:34 PMndelurey says:
If I could only use one, which would be better: an angle grinder or a bench grinder?
Apr 1, 2009. 6:49 AMNebraska G says:
Go with Both and experiment!
Mar 29, 2008. 3:44 PMCountry dude says:
is there a certain fin ness of hacksaws like with sand paper or sand
Feb 7, 2009. 9:15 AMslydark says:
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! =) )
Mar 30, 2008. 5:38 AMCountry dude says:
Thanks man
Aug 31, 2008. 2:03 PMdanoliveri says:
i dont own an angle grinder do i need one? if so were can i get one and how much are they?
Aug 2, 2008. 1:13 AMlaci37 says:
The best tool to cut this type of steel is plate shears.
Aug 5, 2008. 2:33 PMlaci37 says:
Yes, I speak easily with four old plate shears... My family have collected everything over 60 years or so.
May 11, 2008. 6:58 PMlilel says:
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.

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