hey guys,
i have this uncontrollable urge to grind some knife blades out of used lawn mower blades. just because i have enough to get in some good practice.
i know, mystery steel, but this will be good practice for me and i can learn something from using this stuff while grinding and heating and so forth.
so, my question is; any does or don'ts or if you have had experience using this
metal , any good pointers???
any advice will be most welcome.
i don't expect super knives, but some of these blades throw nice sparks,(high carbon).
buzz:D

Most lawnmower blades, as far as I know are 1080 carbon steel. Should make a decent blade. Of course lawnmower blade steel is just as prone to economics and whatever the manufacturer has on hand as any other.

Fred

watch out for cracks-l/m blades here take quite a beating,jimmy

If you were to clean an old blade so it is spotless, no paint, grass, dirt or anything else and hold it close to your ear and tap it with a small piece of metal it should have a bit of a ring to it unless it is cracked, then it will sound dull. If you can find a crack and remove that piece of metal try it again, more that a couple and I would try a new piece.

Ahhh if it's ok as a sword blade quenched in water with no temper it would be a pretty lowgrade alloy for knifeblades---the japanese who use that for swords use about a 1050 steel and even then the treat the back so it doesn't harden during quench.

i dig. so make sure blade stock is not cracked or fatigued.
quench for hard edge. and go from there,
i have in mind a scandi leuku blade a 7-8 incher, and a few puukko's 4-5 inchers for starters.
buzz
thanks for the input. this site rules.:D

Test each one for heat treat on scrap before you heat treat a knife you like. I have a piece of old lawn mower blade that shatters in water.

pt sent. how did we get to this point .???
buzz

When I ran a lawnmower shop, I discovered that the Cub Cadet blades were the hardest to grind with a sidewinder.I expect that the steel used in those blades are superior to most.

J.B.,
The hardness re. grinding could also be alloys i.e. vanadium etc. added for toughness. Not necessarily the best as far as forging blades goes. It's carbon content that makes the difference in hardenability & edge holding.

Larry

When I ran a lawnmower shop, I discovered that the Cub Cadet blades were the hardest to grind with a sidewinder.I expect that the steel used in those blades are superior to most.

there is a cub cadet dealer near here. sooooo....:D

What grade of steel are common lawn-mower (not the "REEL" type, but the Rotary-Type) made of?

the last time I tested any, they were 1080 but like all used/recycled/found steels it can be anything.

I have a student bring in several commercial mower blades that would not quench harden; very disappointed he was.

So I would say a wide variety of alloys and you don't know which!

Hello People
I have used disks from old agricultural "plow" implements with a lot of success, is there a grade I.D. on things of this sort, or is it the proverbial crap shoot. In my old job we had a phrase for this, it was known as a SWAG (scientific, wild xxx guess) but other than the good ol' spark test, how do you tell?
Paul
Its not over... Untill we Win!!!

On the lawn mower blades, I have HEARD that they can be 5160, but I really don't know from personal experience. I have several out in my junk pile. I may spark test them, or use them in pattern welded stuff one day.

ive heard that they were spring steel, never tested though.

The blade on my mower is dead soft and easily sharpened with a file, be surprised if it was not mild steel!

I've seen lawn mower blades bent from hitting rocks (no, it wasn't me...), I doubt they're good steel. And as Arbalist says they sharpen easily, I don't recall ever seeing branching sparks when sharpening them but I wasn't really looking for it.

Good Luck!

Disks will vary too depending on the local soil; some are designed to resist abrasion due to sandy soils and others to resist breaking in rocky ones. My grandfather owned a Case Tractor dealership once...

i have a honda push mower with mulching blade that his summer found a 3/8 grade 70chain it put a cuts in the chain about 1/8 deep and it bearly left a mark on the blade it did stall it but its still cutting grass i think i'll save them blades for some thing when i change them

I believe that you will find that different companies use different types of metal. On my mower when I use the brand of blades that came on it, I need to sharpen them before I finish cutting the yard. But blades from another supplier will cut the yard three or four times before they need sharpening. I’ve worn out several sets of both kinds, I don’t buy the brand name ones anymore.
Tim

I tried to find out what rotary blades are made of and after a while I got the answer, tool steel, carbon steel and mild steel, or just about anything so it's the spark test or even trying out tempering. I know my Snapper blade could be sharpened with a file, so it must have been something like 30 points (30% of 1%). I'm sure it wasn't tempered, if it was 80 point carbon, it wouldn't sharpen with a file and at that rate of carbon, it would spark and chip a lot under the type of impacks the typical lawn mowers run into.

Dave normalized 1080 will sharpen with a file and still be tougher than mild steel for the same object. I've filed D2 before, filing doesn't tell you squat about alloy content.

It's more than just the alloy it is the alloy AND the heat treat that produce hardness, toughness, etc

Why we tested the quench hardness of the blades brought in by my student and I'm perfectly willing to keep on testing them as the *next* one might be higher in carbon than the ones we have tested so far.

I forgot to add, "when tempered." Good carbon steel, like spring steel, can be slick to an ordinary file if it's been tempered for carving wood. I have to use special stones on my small wood carving tools I made from garage door springs, files can slide off without doing much work. I have a car spring punch that's too hard for a file.
As for lawn mower blades, the problem for us to figure out if they normalized a good carbon steel or used a low carbon mild steel for the blade or is something inbetween. As the site I found said, all forms of steel, from mild to tool steel, can be found used in the blades, another site said something about being careful not to lose the temper when sharpening with certain high speed tools. I figure the price of the lawn mower may indicate the quality of the blades, a $49.95 mower is sure to have a mild steel blade, but start investigating the steel quality in the $200 range and above.