Mower Blades?

[kBob]

Last week I got my ZTR mower back from some serious reworking and as it was in the shop anyway had them change the blades. After loading the mower on my trailor I noticed a set of old blades laying next to where I was parked and commented on them to the mower repair guy. He scooped them up and announced he would make a few bucks on them as there was a local "knife maker" that dropped by once a month or so that looked through the pile of scrapped blades for starting material for his blades.

So what about using hard as rock lawn mower blades to make knives from? Can you cut them to shape and do stock removal without softening them first?

I had a buddy ages ago that got mad at me because I delievered oil to a saw mill that had a gigantic broken band saw blade piled next to where I made a delivery. When I commented that it was atlast out of the way as it had been sold as scrap (and that was the first he had heard of it) he became angry at me. Would not want a repeat on the mower blades I have changed over the years and just piled in the pump house ("What kind of people live here" name that film)

-kBob

 

[hso]

You'd want to anneal them, then grind, then heat treat. The hardness requirements for mower blades are pretty different than for knives.

 

[Jason_G]

Most lawnmower blades aren't rock hard. They're usually pretty low in carbon, and tend to be softer, so that they can take a beating without breaking or chipping out badly. That means when you heat treat it, it will probably fail the file test miserably. Lawnmower blade knives have been made before, but I would say get some better steel if you really want to make a good knife. If you just really want to try it (no harm in that), I would cut a small piece, anneal it, and then heat treat and quench it (that's another thing- you'd just be guessing at the heat treat), and see if a file bites the steel or skates across it. If it skates, it might have potential. If it bites, I'd say toss it before you spend a lot of time and elbow grease on something that will never take an edge.

All you can do is try it and see. The joys of mystery steel

Good luck with it.


Jason

 

[Zeke/PA]

Mower blades are in fact Hi-Carbon Steel like 1095 or so heat treated to bring out a balance between "hard" and "tough" to withstand the rigors of mowing.
I have a Blacksmith friend who makes decent knives by first forgeing and re-heat-treating mower blades as one would an Oil quench steel.

 

[hso]

The recommendation to test the steel is sound considering there are all sorts of quality issues with mower blades.

Take a small pice from each blade you're interested in using. Heat it to about 1500 F, you can use a magnet to test when you think you are close and if the magnet doesn't stick heat above that point a little bit more. Quench your test piece in oil like vegetable oil, automatic transmission fluid, mineral oil. Let it cool down and then perform a file test or breaking test on it. To test with a file, use a good metal file on you piece and if it bites easily your steel doesn't harden. If it doesn't bite easily it has. Alternately, break test it by clamping a small portion in a vise and give the protruding bit a moderate smack with a hammer. If it has hardened it will break, if not it will bend. If it did not harden, or did not completly harden, try the test again, but use water to quench. If it doesn't harden you can try brine, but now you're snipe hunting. If it won't harden in oil or water then you're not going to harden it for a blade. That doesn't mean you can't use them for other purposes, just not for blades.

 

[Jason_G]

Mower blades are in fact Hi-Carbon Steel like 1095 or so heat treated to bring out a balance between "hard" and "tough" to withstand the rigors of mowing.

I don't know man, I'm not saying you're wrong, but respectfully, I'd be hard pressed to believe that there are very many, if any, typical lawn mower blades out there, of modern manufacture, that are using 1095 or similar. I'm not doubting that your friend makes a fine knife, but I'm hesitant to believe an across the board statement about mower blades being similar to 1095.

I could easily be wrong, but here's why I'm skeptical:

A mower blade doesn't need to be that hard, and that would be a lot of wasted carbon, and manufacturing overhead, for a blade that doesn't need to keep a razor-honed edge. Those blades are probably spinning at better than 2500 rpm. As long as they stay wedge shaped, and semi-sharp, they'll cut a yard. Add to that the fact that a very hard blade will shatter and possibly send shrapnel across your yard if you hit a rock or the edge of your driveway, or at best crack or chip out badly, and it becomes even more tough for me to envision 1095 for that application. I know some blades are edge hardened, but I'd imagine a blade manufacturer's definition of hard, and a knifemaker's definition of hard are not the same.

I'm betting most are made of some kind of a mid carbon content alloy, somewhere between high carbon steel and mild steel. Maybe 108X at most, which could possibly make a decent to great knife, but that's a liberal guess IMHO. I'm betting less carbon than that.

Like I said, I could be wrong, this is just my WAG, but I would definitely do a heat treat test before assuming it's got enough carbon. Might even try a spark test before that, although that's an inexact science to say the least.


Jason

 

[Zeke/PA]

Jason G,
I chose 1095 in my post because that steel is usually cheaper and readily available to a manufacturer.
The hardness/ toughness of course is determined by the end use of a product and is controlled by Heat Treatment.
A steel with less than .5% Carbon is not considered "hardenable" as the Carbon content is relatively low where in 1095 (.95%) the Carbon content is high and the steel is more "hardenable".
I have several mower blades around and I see a mower blade knife in the near future.

 

[stan rose]

I have tried my hand at a couple of lawn mower blades. I was told by an old timer that the steel was either L6 or 1075, all passed the file test after hardening. As time went on the blade quality got sketchy and a lot of them were being made in China. After thinking on it I decided it was no longer worth all the time to prep and work the steel for something of unknown quality. If you want to practice annealing, shaping and heat treating I'd say have at it, if you want to put a lot of time and effort into a knife spend the money on a good piece of bar stock.
By the way this post is 100 percent opinion of a non-professional knife maker, knife making is just one of my many hobbies. As such there are far more informed posters on this site who's observations should carry more weight.

 

[hso]

I chose 1095 in my post because that steel is usually cheaper and readily available to a manufacturer.

So that was just a shot in the dark?

There are a lot of other steels that are even cheaper (and then there are the "mystery steels"). The forging forums have occasional warnings about making assumptions about modern salvaged steel. Older steels from leaf and coil springs are pretty reliable, but mower blades can be weld ups of junk or mild with just the ends tipped in hardenable material.

I see a mower blade knife in the near future.

Let us know how you heat treated it and how it performs.

 

[meef]

Some folks call it a sling blade, I call it a Kaiser blade

Reckon you make me some biscuits. I like them French fried potaters.

 

[Jason_G]

Some folks call it a sling blade, I call it a Kaiser blade

Reckon you make me some biscuits. I like them French fried potaters.

I likes mustard on my potaters. Umhum.




Stan, I have also heard that they used to be harder and contain more carbon than they do now.


Jason

 

[Zeke/PA]

So that was just a shot in the dark?

There are a lot of other steels that are even cheaper (and then there are the "mystery steels"). The forging forums have occasional warnings about making assumptions about modern salvaged steel. Older steels from leaf and coil springs are pretty reliable, but mower blades can be weld ups of junk or mild with just the ends tipped in hardenable material.


Let us know how you heat treated it and how it performs.

Actually I have a blade set aside that has passed the "heat a corner red and quench" test.
Somebody mentoned using bar stock of a KNOWN alloy.
Obtain some O-1 flat bar stock and have at it.
Easy to heat treat and holds an edge very well.

 

[joshk-k]

If you've got a bit of blacksmithing capability, mower blades make great froes.

Josh

 

[Deltaboy1984]

We made a farm machet out of one back in the 1980's. It still going but we did heat it up good in a ole coal forge and oil quenched it.

 

[mio]

@kbob

twister

 

[theotherwaldo]

I've made bumper brackets, timber straps, miscellaneous brackets and braces, and a machete out of old mower blades. The idea of making a fine knife out of that stuff never occurred to me.

There's better scrap out there for that purpose.

 

[One_Jackal]

Old saw blades are the best for making knives. Old saw blades used to be freebies. Now even the cheapo Chinese decorative saw blades bring a pretty penny. Leaf springs from a truck or 18 wheeler trailer make decent knives as well.

Knife making is something I got out of in high school. You used to be able to buy high carbon steel "blanks" at the hardware store. Now all you can buy is a blank look.