Before my required weekly appointment with the lawn, I had to do some deferred mower maintenance. It is a self-propelled mower that had lost the self part. It was even hard to push. The teeth on the inner rim of the wheels and been mostly ground off. The bigger problem was the the the remaining tooth stubs would bind up against the drive gear and not propel, self or otherwise. The replacements of the wheels and the dust shields was uneventful. This surprised me.
While the mower was on the bench, I decided to check on the blade. I am ashamed to admit when I removed the blade, I had to stop and try to figure out which edge was supposed to be sharp. I don’t think I had been cutting the grass as much as annoying it.
As I was sharpening the blade, I started wondering if I would need to sharpened less often (more than two years) if the blades were made out of better steel. High speed steel (HSS) is a good material for general cutting tools but won’t hold an edge as long as other choices. A2 (air-quenched) is a very hard steel that holds an edge longer but is harder to sharpen. O1 (Oil-quenched) is easier to sharpen but doesn’t hold an edge as well. The chromium content of O1 is less than that of A2 steel and will also rust more readily. And finally Lee Valley’s PM-V11, the relatively new powdered metal alloy. Between A2 and O1 in hardness. The claim is that the powered metal is finer grained and more durable and impact resistant. Might be useful in a mower blade. In that Lee Valley already has a gardening line of products, I should be able to talk them into making the blade.
Now some of you engineer types might have issues with my proposed blade improvements. I will attempt to address them all below.
1. Expense – Rough calculations make me think that a high-speed steel blade would be around $300, A2 or O1 around $400 and a PM-V11 close to $500. If I only have to sharpen it every three years it might be worth it. One way to cut costs is to use the old method of laminating an expensive metal edge onto a cheaper blade body. Planes and chisels used to be made this way and I believe that some Japanese tools still are.
2. Brittleness – Harder steels tend to be brittle. One might think that an A2 mower blade hitting a rock at full speed might cause a catastrophic blade failure. I think after five years I have hit all the rocks that there are to hit. One solution might be to again laminate a hard edge on a softer blade. For additional safety, I might want to have a steel mower deck and not an aluminum or plastic one.
Based on the above discussion which steel would you recommend? (My first poll. How exciting!)
For my second poll, how do you sharpen your your mower blade?
It is easier to see where you mowed with a sharp blade. On the other hand, it is much easier to see shat you missed with a sharp blade. Now there is that whole oil change issue. I read somewhere that you should change your oil every 3000 miles. I’ve had the mower six years and even counting the year I had to mow the lawn of the house we owned and lived in and the house we owned and didn’t live in, I don’t think I have 3000 miles on it. If you believe the Car Talk guys, Click and Clack, the Tappet Brothers (Tom and Ray Magliozzi), I should be able to get 5000 to 7500 miles between changes. It will be interesting to see if the engine fails before scheduled service.
Air filter wasn’t that bad. When I blew and banged it a bit, I could see the paper pleats.
Next, back to furniture.