Are lawnmower blades good for making knives?-Let’s find out!
Some lawnmower blades can be a good option to make a knife, but this depends on several factors. This is because mower blades are made from different types of metals.
And, it depends on the metal if they can be hardened or not.
If the steel of the blade can’t be hardened, then it won’t make a proper knife. Knife blades are made of various materials, with the most common options being stainless steel, carbon steel, alloy steel, and tool steel.
There are other, less common materials such as cobalt, titanium alloys, ceramics, obsidian, and plastic.
Lawnmower blades are usually tempered to ensure the blade is stronger and long-lasting.
The temperature depends on the type of material. For these blades, steel is said to be the most common option, but other frequent choices are alloyed carbon.
Transforming a lawnmower blade into a knife requires some time and skills, but it’s not impossible.
The most inexpensive, easy to work with, and types of steel that have easy-to-follow heat treatment recipes are 5160,1070, 1080, and 1084.
They have at least 0.6 percent carbon, but not more than 0.84 percent. All those above 1084 will make the heat treatment more challenging.
Heat treatment is needed to make the steel harder to be suitable for use.
The degree depends on the blade’s purpose. A blade has to be hard enough to keep the edge, yet still flexible to sustain a continuous and intense use.
Hardened blades aren’t necessarily tempered, yet tempered lawnmower blades may be hardened.
For a blade to be tempered, it needs to pass through a process of hardening. The product after the hardening is known as Martensite. Some may stop at this part, especially if this is their standard procedure.
It may also depend on the reasons for why a hardened blade is necessary.
Tempering shouldn’t be done excessively to prevent it from making the blade too soft, yet help it better its toughness and lower the brittleness. Tempered blades won’t wear out fast and they’re said to be long-lasting.
Hardening and toughening the blade are done together and tempering often becomes necessary to solve the low tensile strength.
Mild steel that can’t harden isn’t knife material. This type of steel is iron with a low amount of carbon. It’s strong, but not enough.
This is low-carbon or plain-carbon steel.
It’s inexpensive and a common steel form because it provides properties suitable for plenty of applications, including being used as lawnmower blades. If you have this type, it may not be the most adequate as a knife blade.
If the lawnmower steel is suitable knife material, here’s how you can make one out of it:
- Cleaning first
Lawnmower blades that are to be repurposed need to be cleaned well. You can use a steel brush for this step.
- Flattening time
Get the metal hot in the fire and using a hammer, flatten it as much as you can. At this point, any grass leftovers will also get burnt off.
A regular wood fire and a hairdryer with additional air will create enough heat to get the metal red.
- Can it harden or not?
The shatter and skittering tests can be useful for this. Light a fire and get a small corner of this metal red hot and dip it into water.
Once it cools down, hit it with a hammer and notice if it’s going to bend or shatter. If it shatters, it’s good for making a knife.
If it remains soft, it may not be suitable. You can also do the oil test (sunflower oil is okay).
Cut off a small piece and get it red hot and then dip it into the oil. Check to see if a file or a Hacksaw can cut into it or scratch it.
- Draw out the design & cut
Check the internet for this-there are plenty of online templates for knives. Cut the paper template and trace it onto the blade.
Some use typex for this step. When the design is onto the blade, cut it out with an angle grinder. Cut as precisely as possible because this will be the knife’s shape.
Don’t cut too much or cut the border too thick.
This will just add to the work when you’ll need to grind it to the shape. Around 1 to 2 millimeters around the border is enough to ensure an adequate grinding edge.
- Time to turn the metal into a blade
Grind the blade to shape following the template and then put a bevel onto it.
Do it slowly to prevent any mistakes. Avoid overheating the metal by working with your bare hands.
If the metal feels too hot, cool it down in some water. It’s very easy to damage the blade’s tip by overheating the metal.
The blade shouldn’t get any blue spots or get very red. Grind the edge not thinner than a millimeter or it may crack during the heat treatment!
- Time for sanding
Do it while the metal is soft and nice, prior to the heat treatment.
Clean up the edge and ensure the bevels are uniform. Remove any scratches from the exposed metal.
Use a coarse 150 grit and go up until you’re satisfied with the look. Remember to drill the holes for the metal pins for the handle.
Now, harden the metal by heating it up so it stops being magnetic, and then dip it into water or oil. That will make it hard, but brittle.
To create a hard edge that will remain sharp and a durable, soft spine, do a differential heat treatment.
For this, pack some clay around the blade to control the speed of cooling down while dipping it.
In order to temper the blade, heat it up to around 180 degrees C. Keep it at this temperature for an hour or so to make the metal softer and more long-lasting.
- Cleaning and sharpening
Use sandpaper onto a tile as a sharpening stone for the edge which is still around a millimeter thick and quite blunt.
Work it until it’s thin enough to use an actual sharpening stone. Begin with 150 grit and increase it as you go.
Once this step is done, it’s time for the “real” sharpening. Opt for your preferred method of sharpening. At this point, you also set up the handles. Here’s how to make them.
The answer to the question “Are lawnmower blades good for making knives?” is “Yes”, but it depends on the type of steel that the blade is made of.
Some types that can’t harden aren’t usually good candidates to be transformed into knives.
Other steel that has been hardened can be made into a knife, of course, if you’re ready for that DIY project. This is a great way to reduce scraps and repurpose the older, worn-out lawnmower blades.