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Re: Reason for Dull Mower Blades?

Posted: Wed Oct 25, 2017 11:10 pm
by John Hasler
Not a hatchet grind. Grinding that .4mm back at 45 degrees will have about the same effect on airflow as leaving it flat.

Re: Reason for Dull Mower Blades?

Posted: Thu Oct 26, 2017 12:35 pm
by spro
Okay then but you understand the main point. I had to understand it. Every grind on the flat will eventually require a deeper grind on the beveled surface. It depends, of course, if new blades are on the menu. Deeper grinds of the beveled edge require attention to the heat generated and that requires quenching. Hey it is stuff you already know. Maybe I enjoy conversing with you.
If the blades aren't straight, it's only a conversation and we cut that xxxx the best we can ( do at the time) and be done with it.
We have better things to do.

Re: Reason for Dull Mower Blades?

Posted: Thu Oct 26, 2017 1:20 pm
by John Hasler
Well, if you are going to maintain that flat as specified you are going to have to grind the leading edge square before sharpening. It's true that my method will use up the blade slightly faster, though.

I worry a lot more about just how to sharpen the knives on my haybine. They cost close to $300 per set (but they aren't made of chinesium like the lawnmower blades) and take an afternoon of grunting and cursing to replace to I don't want to use them up too fast. On the other hand when they are dull yield drops and fuel consumption goes up.

Re: Reason for Dull Mower Blades?

Posted: Thu Oct 26, 2017 3:01 pm
by spro
Somehow I knew but mentioned anyway. Small potatoes with lawn blades compared to your experience with heavy equipment like that. Still, this minor conversation reveals some knowledge beyond a mower blade. Thanks John.

Re: Reason for Dull Mower Blades?

Posted: Wed Nov 01, 2017 11:37 am
by warmstrong1955
I've never gotten too fancy sharpening mower blades. Problem here, is a lot of sand, and too many gopher hills, not to mention some tough weeds.
Problem we had in Oregon, was a whole lot of mole hills, and a lot of grass.
Either yard, the part with real grass, is easy duty in comparison.

I stick 'em in the vise, and hit 'em with a 4-1/2" grinder, and grind 'em sharp. I pretty much maintain the original angle, but will shallow it up if I see rolling of the edges. Cheap blades tend to be softer. Only thing I measure is tip to tip length when done, and make sure they aren't too short.
Then I make sure they are balanced, and adjust with the grinder as required if need be.

Bill