Sharpening large mower blades

[meackerman]

I'd hate to see what the blades on my big rotary cutter look like.  I've hit concrete chunks, twisted T-Posts into pretzel shapes and hit who knows what else.

[daddo]

I made one of these to balance my blades. Using the nail trick, I found out, didn't work at all when compared. I dealt with vibrations and unbalanced blades until then without knowing it.




 
Or one of these works good enough. 

[R Clark]

Remove blade and use a 4" angle grinder. We have a lot of rocks here.
When done, put a long whatever size length bolt in the vise, and hang the blade  on it. You can balance it real easy by taking some off the heavier side.

This is what I do for my 54" mower.  Just sharpened it Sunday before putting it away for the season.  Took less than an hour, including lifting it up, getting the blades off, sharpening them, putting them back on.

As for bevel, it's pretty thick, perhaps more than 45 degrees.  Makes the edge a bit more durable.

I keep three acres cut all season long, and this works well for me.  Only sharpen blades 1-2 times per season.

[bennybmn]

I made one of these to balance my blades. Using the nail trick, I found out, didn't work at all when compared. I dealt with vibrations and unbalanced blades until then without knowing it.




 
Or one of these works good enough. 

I'd love to hear what you used for a taper and magnet to make that. And where you could get that cone thing

[DieselDennis]

Is there a tool that perhaps will chuck into a hand drill to sharpen the blades on my 72 inch mower?  The 3 blades are 3/8 to 1/4 inch thick.  The factory angle on the cutting edge looks to be about 30 or 40 deg.  Is that angle critical? And what about grinding on the flat side?  I have been using a hand held grinder with blades mounted in a vice.
Thanks,
Bill

So what's wrong with keeping up your current practice? 
What do you not like about the way you're doing it now?

[tomsteve]

I'd love to hear what you used for a taper and magnet to make that. And where you could get that cone thing

blade balancer- amazon,ebay, lowes, HD, any mower shop, ace hardware........

[Robert Adams]

Way back when I worked in a friends mower shop we sharpened on a bench grinder and touched up afterwards on a flap sander wheel on the other side of the grinder. 
       Than use any decent balancing jig. But make sure it's level to start with as there are cheapies to need truing before use.
      
          You can use a file but that's an exercise in futility as you will be at it for hours even with a good file as blades are not soft steel and you need to remove more material than you realize.


         I personally don't sharpen blades anymore for my mower. I buy them in bulk on ebay because my blades don't even last a summer before the lift wings are eaten away and thrown off due to the sand here.

[Bill Bob]

My concern is the angle critical or not?  And from what I read it is not.  Another poster said he does not sharpen, just buys in bulk.  These blades are a set of 3 and replacement when needed are over $120.00 not your little riding mower blades at all.   Since there does not seem to be a dedicated tool for a factory angle if that would be necessary I will continue with the grinder and vice.   Thanks to all.
Bill

[Robert Adams]

Nope  the angle isn't critical. Just follow what's there and don't veer way off one way or the other. Also mulching blades are generally considered non sharpenable.

[DieselDennis]

If your concern warrants it, they do make devices that will sharpen those mulching blades to factory specs.

http://www.magna-matic.com/index.html  See their Model 8000.  There are others that do similar things. 

And you're also asking in the wrong forum.  If it matters that much to you, start cruising www.lawnsite.com