blade sharping

scottgardner · Jul 5, 2005

I have a 6 foot finish mower.How do u sharping the blades.I just bought a bench grinder but not sure how to go about it.The tips are rounded off do u just sharpen the rounds or do u grind it all the way back so the blade is str8 across again.How far can u grind the blade back till it is no longer good or safe.

RalphVa · Jul 6, 2005

I run them back and forth, from end to where the beveled edge stops, over the bench grinder lightly and grind down until I get a sharp edge. Do about the same number of back and forth grinds on each side. Only grind the flat side VERY lightly, just enough to remove blunt end damage. If you grind hard enough to slow the grinder or start getting smoke or red or blue metal, you're grinding way too hard. You should be able to grind it and still be able to hold it in your bare hands.

Some hard core folks will tell you NEVER to use a grinder; always use a file. This is fine, but it's a lot of work if the edges are rounded like you say.

This is for a finish mower blade. There have been a couple other threads about techniques to use on brush hog blades that typically aren't ground to a sharp edge.

Ralph

rswyan · Jul 6, 2005

( Some hard core folks will tell you NEVER to use a grinder; always use a file. )

I used to be one of those guys /forums/images/graemlins/grin.gif

Ideally you should build a jig to hold or slide the blade along so that the same angle is maintained for the length of the cutting edge.

I bought one of these:

Delta Sharpening Center

last year specifically to sharpen mower blades with, although I have not gotten around to fabbing up a jug to hold my blades yet. The blades with be sharpened by sliding them over the white wheel from front to back - not side to side. This gives the best finish on a mower blade I've ever seen and is very quick.

Since I learned to use a right angle grinder and have gotten halfway decent with it, I've been using that this year until I get some jigs for the blades built.

rswyan · Jul 6, 2005

Errr ... that was jig not jug

trlong · Jul 6, 2005

( Some hard core folks will tell you NEVER to use a grinder; always use a file. ) 

I'm still one of those guys (at least for now). I had always been told that grinding heated the steel too much and took out the "temper", leaving it more succeptible to cracking, or at minimum dulling more quickly. I know if I sharpen my chainsaw chains by hand file that they stay sharp much longer than if I take them in for sharpening where they use a high speed grinder bit.

That said, the filing is very slow. Now, seeing that Delta sharpening setup, I'd love to save the time and keep all my blades touched up. It does make an incredible difference in the finished job with nice sharp blades vs. dulled and/or chipped blades.

As for how much the blades can be sharpened (i.e. how many times, how thin the width before it's time for new blades), I believe I see a line on my 1060E and my Honda hand mower blades that indicates when it's time to replace. However, I definitely defer to those TBN'ers with much greater expertise for that answer.

Tom

Eric_Phillips · Jul 6, 2005

My F-I-L uses an attachment for his hand drill. He says it beats taking the blades off and taking them to the basement to use the grinder. Now that I have a real mower that will need attention I was thinking of trying the same thing.

Eric

have_blue · Jul 6, 2005

( >Some hard core folks will tell you NEVER to use a grinder; always use a file. >

I used to be one of those guys /forums/images/graemlins/grin.gif )

You still are.

The only time you need precision sharpening is on mills, drills, and other machine tools. A mower blade needs to be fairly sharp and balanced, but eyeball is plenty good enough.

Come to think of it, "eyeball" is how you find out your fixturing and measuring devices are not accurate!

That's been my attitude since I discovered that all that care precision is long gone after the first circle is mowed around the field. /forums/images/graemlins/shocked.gif

Just pulling your chain RS. I've been known to use use more precision than I need myself. I still sometimes carry a caliper and micrometer to the hardware store. It rally freaks out the clerks. /forums/images/graemlins/smile.gif

Tom_H · Jul 6, 2005

( My F-I-L uses an attachment for his hand drill. He says it beats taking the blades off)

The disadvantage of not taking off the blades is that you are not able to balance them. If one side winds up being significantly more heavy than the other, you can get a lot of vibration which is not good for the mower or the tractor.

There are balancing devices from cheap to expensive. I find that a finish nail in a garage wall stud suffices well enough for me.

scottgardner · Jul 6, 2005

When i say rounded i mean the outer edge or tip that at a 90 angle.This is to very outer tip that cuts the grass first In order to get it back in shape i will have to grind back a half in. or more.Do u grind it back or just give it a sharping it. Its my thinking that if it is rounded at the tip it has shorting the blade and my leave uncut grass.It is not the whole outer edge but just the tip.In my thinking as the blade spins in a circle with the tip gone it is a shorter blade.

have_blue · Jul 6, 2005

( In my thinking as the blade spins in a circle with the tip gone it is a shorter blade. )

Well, you are sort of right. However, it doesn't shorten the effective blade diameter much. Maybe 1/16th" or so per side for a well-worn blade. You can't restore the lost length by squaring it up.

I wouldn't worry about the corner being rounded off. Just follow the contours when you sharpen it, and it will cut fine. Squaring it up would waste time and blade life, and it wouldn't cut a bit better.