Instructables
Picture of Creating a Knife From a Lawnmower Blade
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The shop I work at  recently got a whole bunch of lawn mower blades so I have been trying to find things to make them into. One of the things that occurred to me was if lawn mower blades are strong enough to hit a rock then they might be a good candidate to make knives.

In addition to the instructions on making the knife I will include an explanation on how I replicate the knife design. (I ended up making 4 of the same ones)

These steps are not exhaustive and assume the maker has experience with some basic metal working tools.


Tools used

-Plasma Cutter
-Angle Grinder (with different grit flap disks)
-Bench Grinder
-Die Grinder


Materials

-Knife Template
-Lawn Mower Blade
-Sharpie
 
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Step 1: Safety

Picture of Safety
Remember when working with power tools to use the proper safety equipment.

In this case it would include:
Safety Glasses
Respirator  (remember grinding disks are putting many nasty things in the air)
Earplugs

Optional
Gloves (although not necessary and not for use when working at a forge I like to use a good pair of leather gloves to lessen the vibrations when I am working with grinders.)

Step 2: Making/Tracing the pattern

Picture of Making/Tracing the pattern
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If you do not have a knife already created that you wanted to replicate then you need to design a knife outline.

To get an idea of what kind of designs work I would suggest first cutting different patterns out of cardboard and seeing how they fit in your hand. Then when you have prototype you like then you can transfer this by simply laying your template on the lawnmower blade and moving it until it fits. Now just trace your template with a sharpie and you are set to cut it.
Schmidty161 year ago
very creative
Schmidty161 year ago
very creative
jbrauer1 year ago
This is a really cool design, but a shame it isn't heat treated. Here is how you can do it with a propane torch and a kitchen thermometer:
1) Heat the metal red-orange hot, until a magnet won't stick to it.
2) Quench it in some oil (including corn/canola) that is at about 280F.
3) Polish it to bright metal so you can see the colors.
4) Heat the spine (not the edge) of the blade with the torch.
5) As you heat, watch for the cutting edge to heat up to a straw-yellow, almost purple color. The spine should be a darker blue.
6) When you get to straw yellow, quench it in oil again.
7) Polish and sharpen.

There are other ways to accomplish this, but this is a basic DIY that I've tried and works.
sonicdrive1 year ago
a easy trick to get a good harden steal edge is to weld it with some chromium steel rods on the edge and temper it once you have the shape you want a solid bead will last a long time just my 2 cents
rimar20001 year ago
All lawn mower blades I know are mild steel, in order to diminish the risk of it breaks. Hence, the edge never will be a well sharp one. I reinforced the edge of mine with hard steel to avoid sharpening it so frequently.
HeWhoMakesStuff (author)  rimar20001 year ago
I have been doing some research into lawn mower blades and it seems that they are made of tons of different kinds of steel. I ran across this forum where no one could decide what the majority of lawnmower blades are made of. I am going to put a nice edge on mine and see how it holds up, that should help me figure out what kind of steel I am working with.
Forum I was talking about URL: http://www.bladeforums.com/forums/showthread.php/657675-lawn-mower-blade-steel
Well, while I was writing my comment I thought that possibility. I can't say I know the matter, I have seen only some blades, but all of them was mild steel. They lose the sharp edge very easily.
ZaneEricB1 year ago
Very nice! I had to reharden my blade i made out of garden shears. I did it in a BBQ pit after grilling some steaks...quenched it in some cooking oil, so it would have that carboned finish.
I like what you have done here....
Gregbot1 year ago
EXCELLENT! THANKS! (yes! I had to shout that!)
mdaniel51 year ago
Lawn mower blades are never a tempered steel, because of risk of fracture caused by accidental rock that may hit it. If you want some good knife steel you want to use old lumber bandsaw blades, they are durable, but will also hold an edge much better than a lawn mower blade.
HeWhoMakesStuff (author)  mdaniel51 year ago
I have heard about those band saw blades working well. I just need to get my hands on some....

I did try tempering one of the blades I made a discovered that the lawn mower steel tempers much harder than mild steel.
Kiteman1 year ago
That's a nice "fantasy" shape, but it doesn't look comfortable to hold - maybe wrap the handle end in strips of leather?
HeWhoMakesStuff (author)  Kiteman1 year ago
Its actually surprisingly comfortable, but I am designing a handle and sheath for it. Probably made of wood and leather.
Cool - next instructable?
HeWhoMakesStuff (author)  Kiteman1 year ago
yep probably in a week or so