Make a Lawn Mower Blade Knife

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Introduction: Make a Lawn Mower Blade Knife

Make a sweet knife out of a old junk lawn mower blade .

Step 1: Things You Might Need

Tape measure , square and or straight edge, pencil and marker, grinder , cutoff wheel, flap wheel, grinding wheel, and a couple of different sanding discs for starting the polishing finishing process, clamps for holding the material , A bucket of water would be helpful to for keeping the material cool. And one good lawn mower blade. For more detailed work a dremel tool may be handy.

Step 2: Make a Design

In this step you can use a piece of cardboard or paper for a pattern if you would Like. I just freehanded my knife. Use your imagination here. A blade is a blade you can make it as simple or as fancy as you desire. I draw them in pencil first so I can make corrections and then trace over with marker.

Step 3: Cut Your Part Out

Clamp your part so it does not move. Use your cutoff wheel to make the basic shape and take your time so you do not build up too much heat. Use your bucket of water to splash the part occasionally to cool it down . You do not have to take all the material off at this time, use your grinding wheel to make your finishing shape.

Step 4: Make Corrections to Your Shape If Needed

Hold your knife and change your design as needed . Make sure it is comfortable to hold and use. Use your flap wheel to help finish your design it will take off less material and be easier to use.

Step 5: Make a Edge

Take your grinding wheel and cut your Edge . Take your time to not build up heat because the sharper it gets the thiner the material will be and the hotter it will get.

Step 6: The Finish of Your Knife

At this point you can finish it how you would like, I used my sanding disc to clean smooth and polish my knife . I then used polishing compound and a buffer to get a shine. You could also sandblast and paint your knife .

Step 7: Sharpen and Enjoy Your Knife

Resharpen your knife with a stone or other sharpening devise . At this point you're done enjoy.

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    42 Discussions

    Watch movie King Arthur. A scene shows a decapitation with a very large sword if true imagine how sharp for such a large thick blade must have been. Point is to me doesn't matter the quality of steel just the sharpness and what you will be cutting I have had a lawn business so my job is to cut things YES or NO???????

    6 replies

    Actually broadswords, bastard swords, and the two-handed style blades had a edge so dull you could run your hand down it and it wouldn't leave a cut. It was the size and weight of the weapon that produced to cutting action. There is a great documentary on the Viking Ulfbert sword. They had a demonstration with a katana and then a broadsword. The demonstrator actually did run his hand down the broadsword blade and leave very neatly chopped a tatami mat in two just as he did with the katana. I recommend this video to anyone interested in swords and ancient weapons.

    that isn't entirely true, they did HAVE a sharpened edge, it just wasn't razor sharp, but they were sharpened every day after the knight trained (they were made from inferior iron). whereas Katana's were made from what we know as Damascus Steel, it was extremely hard. and they had a concave blade. (so basicly there were to microscopic blades)

    I have to respectfully disagree. I have seen demos by European weapon masters. There was a great one at the Tower of London, and another in Cologne, Germany. The swords (broadswords) had edges but not anything you could cut yourself with by running your hand down the blade. The cutting power was from the force of the blow and the angles of the cuts. I have no idea where you heard that broadswords were made from inferior iron. But that is patently false. Iron swords were older, from a different time. True, Japan, China, and the Middle East had access to better steel earlier than European countries, but we are talking about the early Dark Ages. Later periods caught up with the expansion of trade. Think the First Crusades. Though even then, swords were of good steel. Just not great steel. So was the armor for that matter. Later swords were made of higher quality steel. Some were even made with damascene or pattern welded steel. During Renaissance times the swords in Europe were every bit as advanced as Japanese Katana, as this was around the time period the Katana came to the pinnacle of it's art. But they were not broadswords! Compare a broadsword to a late Italian long sword or a cutlass and you'd be surpirsed.

    A blunt sword is completely useless! Theres no cutting Power on a dull edge, no matter jow big or heavy your sword is!!!

    That depends on what you define as dull. Different tools have different relative scales of sharpness. A knife's edge isn't gonna be the same as a sword or an axe.

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    lkay5

    3 years ago

    GREAT instructable! I didn't have to fill in the gaps with my imagination! you walked me through it perfectly! now, I'm off to buy a new blade for my mower so I can make a small axe and a knife with the old one. RECYCLING HAS NEVER BEEN THIS MUCH FUN!

    I honestly would love to try this I will content how this would go after trying it in the summer.

    Popular mechanics used to publish articles on how to temper or harden blades. Basically you hear it then drop t in used motor oil. It'll add carbon and harden the edge. You can use the same method to harden a wood drill bit to drill steel. Google it.
    But here's one on blades:
    http://books.google.com/books?id=0uMDAAAAMBAJ&pg=PA105&lpg=PA105&dq=popularmechanics+tempering+drill+bits&source=bl&ots=rFioJOV48y&sig=rDAIDrFvAXRHUa5N-EZOyJyroGY&hl=en&sa=X&ei=6bM8VJ3UDKjH8AHKwIHoDg&ved=0CC0Q6AEwAw

    I have some small gardening tools I had custom forged in Korea from car springs several years ago that work excellently, and have never needed resharpening. They quickly developed a thin layer of rust, but it seemed to protect the tool from further rust. I just went to look at the tools, and discovered that they had been put away with dirt on them 2 years ago. After scraping the dirt off, they looked like they did a month after I got them. By the way, all the hand scythes the rice and wheat harvesters use are made by the same forgers using the same springs. They are very inexpensive, too. I think in the mid 1980s, they were about $1.75 each.

    A lawnmower blade is a poor choice for making a knife when you spend your time doing the same thing with a better steel that will hold a sharp edge.

    With the discussion on steel quality going on I cant help recalling a National Geographic documentary (or was it Discovery) on Japanese swordmaking in which the making of a traditional sword was compared with an american sword maker making it.
    The Japanese craftsman had to preorder steel that was only mined in small quantaties once every two years. I think he basically got it as a raw block of iron and he spend a loooooong time hammering it, molding it, folding it etc etc. then went to a process of covering parts of the blade with clay in the hardening and tempering process, then finally had a high quality sword made according to age old tradition.
    the american sword maker, just ordered a band of high quality steel, went to work with an angel grinder and a laser cutter (or a plasma cutter) to get to the raw shape. Then started forging it, using liquid nitrogen in the hardening and tempering process.
    In the end he had a high quality sword made by modern methods.

    So... which one was better. ofcourse they were tested and compared... they were basically equal in quality albeit that with one test the Japanese sword chipped off a piece of the cutting edge..... but the modern made sword was a hell of a lot cheaper and faster to make :-)


    With regard to the tempering/hardening of the lawnmower blade, I just do not know the quality of the steel, but I guess that even if it would be a softer blade, you'd still be able to skin a cat with it. ('skin a cat' meaning 'getting the job done')

    3 replies

    Are you sure you're remembering that documentary right? Because the real samurai sword making masters do not order their steel, they smelt it themselves in a ritual ceremony. Perhaps they order some metal stock for supplying the tourist trade though? Got to pay the bills too after all.

    i can only state what was in the documntary. His 'order' was on an amount of ore that was dug up once every two years. It isnt that he ordered a plate of ready made steel. just the ore. If he then processed that himself I do not recall

    If there is one thing that I have learned over the course of my life it is that not all steel is equal. Neither is the quality of the job that they can do for that matter. With the best of blades you could skin a whole herd of cats.

    Lawnmower blades are made out of mild steel. Lawnmower blades are soft so if you hit something hard they do not shatter, and break. A lawnmower blade that shatters, and breaks could be potentially pretty hazardous if it happens while the lawnmower blade is spinning.

    I hit a chunk of concrete mowing some tall grass in my backyard once, the blade bent like a hook. So I took it off the tractor and hammered it back straight again. Yehaw! I should add that I took that chunk of concrete and tossed it into the woods a bit. I don't want to hit it anymore when I mow.