John Deere Mower Blade Steel?

T

The Mighty Ginsu

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Aug 11, 2016
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Does anyone know what kind of steel John Deere mower blades are made from? I inherited a pile of them when I got this house. I would probably get about five bucks on Craigslist for the lot of them, and I will never use them on the mower because I now have mulching blades.

They must be really tough. I ran into a partially buried rock the size of a football. The mower ripped it out of the ground and threw it several feet, and when I looked at the blade, it was hard to tell where it hit it.
 
Knives are sharp .. mower blades are tough …. different types of steel.

Normally, mower blades do not make good knives. You can contact the company and ask Tech Support what the steel type is. You will need the part number for your specific blades.
 
I have no idea but recycled steel makes me nervous. I'd never sell anything unless I knew what it was. You could try spark testing it. Might give you some indication.

 
John Deere claims its blades are high-carbon steel with nickel added. I have been Googling around, trying to find out what nickel does to steel.

I found a site which lists characteristics of steel with added nickel. It lists increased toughness, abrasion resistance, and resistance to warping when quenched. If it can be quenched, then I assume it can be hardened to some degree. Unless there is some other purpose for quenching.

Maybe it would be okay for things like hatchets, or just for forging practice. I guess if a blade can rip a large buried rock out of the ground without significant damage, the steel has to be okay for garden tools.

I would feel funny dragging 30 pounds of steel to the dump when it could be used for something. If it can't be forged, maybe it welds or machines well. I need TIG and stick welding practice, so there's always that.
 
JohnDeere supposedly uses very good steel for their equipment,but different steels for different applications. What Have heard ishat the steel that they use fo rtheir output shafts some of the best 5160 made. Soti would be worth your time to find out what else they might use.
 
I wonder if John Deere has their mower blades made in China like most of the other mower blades? If so, I suspect the "high carbon" would have varying carbon contents depending on the batch made.
 
And, there is John Deere and then there is JOHN DEERE.
 
If you do contact them, There is a good chance you are the fifth "Forged in Fire" Fanatic they dealt with that morning and they wont readily know and/or dont want to take time to answer.
Answering, "sorry, its trade secret, proprietary alloy or similar" so they can answer the next call.

Mind you,
I dunno care what you or anybody else thinks of the FiF TV show, But its generated loads of non-productive traffic to manufacturers technical help centers.

Fwiw,
As mentioned, treat mowerblades as crapshoot of mystery steel.
They might turn out as great tools, Maybe not...its seat of pants exercise.
 
The home use mower blades are not useful for knives, for the most part. The industrial equipment used along hiways etc. are more likely to be useful.

I have a Husqvarna landscaping duty riding mower and I couldn't get the blades to Rc60, iirc. This was 6 years ago, but I spent a whole day trying different temps, even brine.

The entry level equipment is all made overseas, and branded for each company. The professional level equipment is different.
 
The John Deere power shafts are the best round forging steel you can get for a tough knife. I still have a bundle or two in the shop for fully forged blades make from round stock. There is a lot of metal in a 6" piece of that shaft. Enough to make a Bowie knife.

I have never been a fan of mower blade knives. You may get it hard ... or maybe not. It may have a good edge ... or maybe not. That isn't worth the time just to save a few bucks on steel.
 
I am sure John Deere uses the very best mower blade steel they can get. The issue is that mower blades are made to be very tough and to not break. These are accomplished by different metallurgy that the atributes we want in a knife blade. Also, mower blades are normally only in the lower Rc50 at best. I suspect that some could be made harder, but most mower blade knives I have seen or heard about have not hardened nearely as well as the maker desired.

If you have a tractor supply and repair place around, you may be able to get some John Deere power shafts for free. These are pure gold for knifemaking.
 
John Deere advertises that their mower blades are made from the same steel used to make automotive leaf springs and are tempered to a lower hardness for toughness. This is different than a lot of other mower blades made from lower carbon alloys to be cheaper while being at that lower hardness.

I have forged multiple blades from John Deere mower blades with good results treating it as 5160 heat treating in the forge. I do not have a hardness tester, but file testing and ongoing edge holding in actual use tell me it worked well. I have also tried with a couple different types of mower blades people gave me and the result was not the same. Based on my experience, for hobby use John Deere mower blades work great and any other mower blade isn’t worth your time.
 
10B38 is a common lawnmower blade steel. https://patents.google.com/patent/US5916114A/en

You said J.D. claims the steel is high carbon with nickel. If that claim is true, then it is probably something like 4340. https://jdparts.deere.com/partsmkt/document/english/pmac/4382_fb_Lawn_Mower_Blades.htm

JD's claims are somewhat eyebrow-raising, because they claim the steel is (a) nickel-bearing, and (b) the "same steel used for automotive leaf springs." 5160 is the steel used for leaf springs, but 5160 contains no nickel. Hmmm.

Keep in mind that formability is a required material property for lawnmower blades.

If you have so many, and you're serious about using them, then send a piece to a lab for composition identification.
 
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Sending them to a lab would kill the goal of getting free steel.

I may harden one end of a blade and see what it's like. I just tried a file on one, and it cuts, so they're not hard now. Of course, I don't know what to use to harden them. I guess oil is the safe choice.

The nickel claim comes from a John Deere dealer's site. I have not seen the leaf spring claim from anything resembling an official source.

I don't understand why these things are here. They look perfectly fine, but they were removed, replaced, and stored anyway. I have a total of 9 spares.

I am planning to weld gussets on a 3-point attachment. These would be great for that purpose, assuming the steel welds well.
 
From the patent: “Furthermore, although the Marquenching heat treatment process has been disclosed, other conventional heat treatment processes may be used to increase the hardness of the boron steel blade into the range of 48 to 55 Rockwell C.” That is consistent with my experience heat treating mower blades.

They compare it to 9255.
 
P.Brewster's link here: https://jdparts.deere.com/partsmkt/document/english/pmac/4382_fb_Lawn_Mower_Blades.htm
The following lines are right at the top of the above linked page. Isn't that a John Deere official site? Auto leaf springs have always been said to be 5160, but isn't there a chance the new leaf springs could have nickel?
- Made from high-carbon, nickel-alloy steel
- Same steel used for automotive leaf springs.

Edited to add: As of Nov, 2020 the first link is broken or requires to log in to access info. Here's another link with same info: https://tinyurl.com/yy36vcfk
 
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