blade sharping

[scottgardner]

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]

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]

</font><font color="blue" class="small">( Some hard core folks will tell you NEVER to use a grinder; always use a file. )</font>

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]

Errr ... that was jig not jug

 

[trlong]

<font color="blue">( Some hard core folks will tell you NEVER to use a grinder; always use a file. ) </font>

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]

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]

</font><font color="blue" class="small">( >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 )</font>

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]

</font><font color="blue" class="small">( My F-I-L uses an attachment for his hand drill. He says it beats taking the blades off)</font>

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]

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]

</font><font color="blue" class="small">( In my thinking as the blade spins in a circle with the tip gone it is a shorter blade. )</font>

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.

 

[PineRidge]

We find it easy to remove the blades and hit them with an angle grinder. Once they are sharp a nail driven into the end of a 2 X 4 and held in the vise will suffice for the balancing job.

We do use a hand file on the backside of each blade to remove any burrs.

When you are doing the sharpening just don't bear down on the tool so hard that you overheat the blade. A damp rag can always be used in a pinch if the blade starts to get to hot.

Before balancing each blade use a stiff wire brush to knock off any dead grass or rust that has accumulated on each blade.

The blades will then cut just like new and without excessive vibration.

 

[rswyan]

</font><font color="blue" class="small">( You still are. )</font>
Well blue .... you are probably right /forums/images/graemlins/grin.gif

Truth be told, when I put the MMM back in service this season I did hit the blades with a file .... they were in pretty good shape from last season and just needed a little clean up.

</font><font color="blue" class="small">( 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. )</font>
It is amazing how quickly a really, really sharp blades will dull - razor's edge might not be the best thing.

When I picked up my tractor originally the dealer told me I might want to sharpen the blades as Kubota doesn't put much of an edge on them from the factory. When I took the mower out of service at the end of last season I had a chance to scope them out - he was right - the edge wasn't sharp at all ... it was flat .... about 1/16th or 32nd high. Even so I was really pleased with the cut .... very clean, with no frayed grass. Probably the blade tip speed,

</font><font color="blue" class="small">( Just pulling your chain RS. )</font>
No problem ... it needs pulled every now and then /forums/images/graemlins/grin.gif

</font><font color="blue" class="small">( 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. )</font>
Yeah .... but ain't it fun ? /forums/images/graemlins/cool.gif

 

[have_blue]

</font><font color="blue" class="small">( It is amazing how quickly a really, really sharp blades will dull - razor's edge might not be the best thing.
)</font>

Well, I'm amazed at how long my blades stay sharp. Really, try it. Sharpen the blades extra sharp and reduce the blade RPM by 20%. If the metal in your blades is about like mine, you will be amazed at how much better they cut and how much longer they stay sharp.**

**Make sure the deck is tilted forward a degree or 2 so you don't re-cut the grass. I suspect this is a major culprit in short blade edge life.)

 

[rswyan]

</font><font color="blue" class="small">( Well, I'm amazed at how long my blades stay sharp. Really, try it. )</font>
Actually I always have ... on the Simplicuty commercial ZTR and Cub Cadet 782 - for some reason the blades seem not to stay sharp all that long when they have a razor's edge on them .... maybe it's the angle I was sharpening them or something ......

But I was amazed at the blades on the Kubota MMM when I looked at them at the end of last year ... they basically looked new ......

</font><font color="blue" class="small">( **Make sure the deck is tilted forward a degree or 2 so you don't re-cut the grass. I suspect this is a major culprit in short blade edge life. )</font>
Yeah, I did handle this at the end of last season on the Simplicity .... there's a set of check chains that controls the rear deck height .... I raised them up by one link. The Cub is undergoing restoration at the moment.