Sharpening lawn mower blades?

[98sierra]

Hey guys, buddy of mine has trusted me to take his blades to work and make them nice again. Plan to sharpen and balance as best I can.

What tool do I use? Bench grinder with stone wheel? 4 1/2 grinder? File? (Hopefully not a file.. Quite a few blades LOL) also, what angle is best? How sharp do you get them?

These are going on a new kubota zero turn used for business. Cut anything from rich people's manacured lawns to jungle status grass.


Thanks in advance!

 

[zkling]

Speechless.

 

[Bikes&Bowties]

Well keep the factory angle. And just go till the Knicks are out of it. Sharp enough to cut yourself but not a razor edge. I use a 4 1/2 inch angle grinder and just hold them in a vise.. If they are to beat up just tell him to buy new ones... If its his business.. That's part of doing work

 

[zkling]

I guess my initial comment may have been a bit rude. I'm just kinda shocked that you are going to be learning on something that a friend's income depends on.

Key is to take off as little as possible. Clean them well with a wire wheel or the like then sharpen the cutting edge then balance. When you balance them balance by taking material off the end, NOT the cutting edge.

For really dinged blades I go to the bench grinder and a stone. Finish off with on my belt grinder.

For touch up a med grit flap wheel in a 4.5" grinder works pretty well. Will put a nice durable, yet very sharp convex edge on them. Don't forget to watch the burr on the backside.

Since you will be doing this on a routine basis, invest in or build a good quality blade balancer.

 

[98sierra]

Thanks guys.


And this is his weekend only business, he rides the zero turn and I carry around a weed eater and blower lol. And he has new blades, these are a few old blades I'm going to rejuvenate and save his wallet some pain. I think he said it costs like 180 to get 3 GOOD blades

 

[zkling]

I'd start with a med grit flap wheel on a 4.5" grinder. Just make sure to lock the blade down somehow. If that ends up being too slow then go to the bench grinder. Remember it is always easier to remove more material than it is to add it back on.

Do not over look the importance of balancing, especially on larger blades.

 

[98sierra]

These are smaller blades. There are 3 and I guess there probably ~20" each. Still plan on balancing just because of how fast these are spinning. To take material off to balance, take it from the end of the blade or the back side, exactly opposite to the side I'm sharpening?

 

[A_Pmech]

To take material off to balance, take it from the end of the blade or the back side, exactly opposite to the side I'm sharpening?

Don't over-think this.

Just keep sharpening the heavy side.

 

[98sierra]

Lol ok thanks guys.

 

[jeremy v]

One thing to remember is that you are not sharpening a kitchen knife. You really do not want the blade too sharp or else the leading edge will just fold over the first time the blade accidentally scalps a little bit of dirt. If that happens the blade will cut terribly. If you think more along the lines of the blade being ground at a pretty steep angle (just like it is when new) and making the edge as sharp as something like a good butter knife you will be much happier in the long run. It will still cut the grass cleanly but the blade will stay sharp for much longer because there is now almost no chance of the leading edge folding over on you if you accidentally skim a little bit of dirt, bark, etc.

Also, one thing I notice a lot on used mowers is that many people add a bevel to the bottom edge (grass side) of the blade to save time by removing less total metal. Never add a bevel to the bottom edge, that just increases the chance that you will tear up the freshly cut grass tips as the blade spins. Take the time to grind back the entire top bevel at the same angle it was when new until the edge is fresh and clean again.

Make sure you balance the blade as well, as was mentioned already. One thing to keep an eye on is that the blades on a lot of mowers have quite a bit of side to side play when remounting the blade to the mower. The bolt holes in the blade itself are usually noticeably larger than the mounting bolt diameter. Try your best to keep the blade centered when bolting it up. All your time spent blade balancing might not amount to much if the blade ends up being mounted 1/8" off-center on the mower shaft because of the extra play in the mounting bolt holes.

 

[Skin]

I tend to prefer a belt sander since it gives a nice smooth looking polish. Just use the original edge as a guide and dress it up. Don't try too hard to get a razor edge, with all the abrasives that get kicked up while mowing they'll lose their extra sharpness by the end of the first job.

I don't worry much about balancing unless im grinding a lot of material off and in most of those instances its often easier and more cost effective to just replace the blade.

 

[lilscorpion]

Don't over-think this.

Just keep sharpening the heavy side.

Back in the day (during summers between college semesters) I ran a maintenance crew and we mowed full time. We also sharpened out own blades because it wasn't cost effective to do otherwise. The entire time I did it, I never officially balanced the blade. I tried to take equal amounts off of both sides but that was all there was to it. Never had a problem. Course stone on a bench grinder. Nothing more.

 

[babyman1737]

Use a bench grinder.
Balance blades on a sharp knife on the center of the blade. If you take care to take off the same amount on each side, balancing shouldn't be an issue.
I run about 500hrs a year on my ZTR mower for the last 7 years. No problems at all.
I pay about $12/blade, 3 blades on my 61" deck.
I can get maybe 5 sharpening cycles on my blades before I have to throw them out.
The factory recommends sharpening every 8hrs, which is crazy. I sharpen about every 30hrs.

 

[cassidy]

I use a nail I have pounded about half way into my interior shed wall to balance them. I hang the blade from the mounting hole and which ever side is heavier will hang lower.

 

[jmm]

I just use a file, after I've cleaned the grime off with a wire brush. It's easier for me to follow the angle, and keep true to it if I don't use power tools. Taking such a small amount of material off, I can usually count on the balancing part being easy (or not having to balance them at all!).

But if I were in the business of sharpening lawn mower blades, the whole process would incorporate power tools.

 

[Buckgnarly]

Back in the day (during summers between college semesters) I ran a maintenance crew and we mowed full time. We also sharpened out own blades because it wasn't cost effective to do otherwise. The entire time I did it, I never officially balanced the blade. I tried to take equal amounts off of both sides but that was all there was to it. Never had a problem. Course stone on a bench grinder. Nothing more.

This...we also mowed commercial, Dixies, Gravelys, and Exmarks. Mowed some pretty damn fancy yards in The Main Line outside Philly. Never once balanced, never really got the whole **** balance/polish procedures I hear I guess to each his own, but we banged out the blades every couple of days with a bench grinder before heading out, would have taken forever to balance every blade.

 

[ToocoolZ28]

Coarse stone on a bench grinder, balance on a small nail driven in the side of the bench.

 

[Andybull]

I worked at a lawnmower shop while still in Highschool back in '68. We used a 10" bench grinder, which is the size grinder I still use to sharpen all of my lawnmoer blades. I set up the tool rest in a way that the blade cutting angle is always achieved. I'm **** and this is what I use to balance the blades:
http://www.magna-matic-direct.com/MAG-1000-Blade-Balancer-p/mag-1000.htm
BTW, balance by taking material off of the cutting edge, keep quenching in water as to not lose the temper.

 

[cidermill]

8 inch course wheel witha good tool rest, blunt grind (90) first to get out nicks, then set angle and slide back and forth on the rest untill sharp, equal strokes both side. if the back of blade (lift) is worn thin throw them out!~

 

[Chuck122]

Flap wheels on a 4-1/2 are your friends. They don't create as much dents as grinding wheels and tend to keep the heat down. I have had great success with the walther ones. They are my go-to for axes, hachets and the likes. I assume they'll give you good results

 

[98sierra]

I did them earlier today. Started with coarse stone bench grinder and finished up with a little finer stone then for good measure got the ole file out and pretended I was making it better for about 3 minutes. Installing tomorrow AM and goin to try them out all damn day long LOL will post back how it works.

 

[98sierra]

And these blades were horrible btw. Couldn't even tell which side was for cutting because they were so dull

 

[Farmall 1066]

Worked for one of the nations largest Deere power equipment dealers. Mondays, we'd have a mountain of blades to sharpen. We had an actual blade sharpening machine, but could do a better job, faster, with an a angle grinder and flap wheel.
If you sharpen a blade according to Deere's Reccomendations, your customers won't like it, but they last longer. I think they suggested leaving a 1/16" thick edge. They wear better, but customers want them razor sharp.
Used to have lots of them bring in blades after each mowing to be touched up. At $7/blade, that was a moneymaker!

 

[ssentt]

File.....30yrs sharping my own blades.

 

[Haveblue]

And these blades were horrible btw. Couldn't even tell which side was for cutting because they were so dull

Were they really so bad that there wasnt even an original angle there? Were the ends rounded? If so, its time for new blades. Its hard to tell without pics, but give em a try and let us know how it goes!