How often do you sharpen or replace mower blades?

[sixdogs]

My current mowing setup is a 7 ft pull type Woods RD8400. Recently I put new blades on and the difference in the grass quality is amazing compared with the "before" blades. I mow at 3 1/2". The mower also doesn't clump the grass clippings any more either but distributes them evenly. I'm now sold on sharp blades.

I know to sharpen them when they are dull and need it but how often is that for most people? And do a given number of sharpenings mean you replace or do you just keep sharpening as long as there are no nicks in the blades? I hear everything from four times a season to every four years. What do others do?


Also, the owner's manuals say to not sharpen the blades to an edge but, in effect, leave them with a dull radius. Why? It doesn't sound right so it that advice just a liability issue?

 

[k0ua]

My current mowing setup is a 7 ft pull type Woods RD8400. Recently I put new blades on and the difference in the grass quality is amazing compared with the "before" blades. I mow at 3 1/2". The mower also doesn't clump the grass clippings any more either but distributes them evenly. I'm now sold on sharp blades.

I know to sharpen them when they are dull and need it but how often is that for most people? And do a given number of sharpenings mean you replace or do you just keep sharpening as long as there are no nicks in the blades? I hear everything from four times a season to every four years. What do others do?


Also, the owner's manuals say to not sharpen the blades to an edge but, in effect, leave them with a dull radius. Why? It doesn't sound right so it that advice just a liability issue?

This is just my opinion.. so take it for what it is worth. I don't mow a large amount now where I live so I sharpen the blades once a year. But my mowing is about 12 hours per year. When I had a large place to mow, I would mow about 12 hours in two weeks. I would sharpen the blades in about the same time period or at least every 20 hours of usage.

Dont sharpen them razor sharp, Just a decent edge, but not sharp enough to slice your skin if you touch them. The best way I have found to sharpen blades is with a hand held 4 1/2 inch angle grinder with an 80 grit flap wheel. I will never use a bench grinder again for this task.

If there is a bad nick I leave it, and concentrate on keeping the overall straight configuration of the edge and sharpen to a moderate edge. In other words, don't grind off a ton of metal to get that one nick out.

 

[Mikeeemo]

Ditto!

 

[RandyT]

Oregon, the largest mower blades manufacturer in the world has what they call the 30-30 rule. Which means sharpen the blades at a 30 degree and and leave a .030 blunt edge on the front. A thin leading edge will dull very quickly, which results in the .030 edge anyway.

You want to remove enough metal to produce a uniform edge but nicks and chips will have little to no effect on cut quality. Most grass is cut with the last 1/16" of the blade tip.

 

[ovrszd]

The blade will hold it's edge longer if sharpened to a dull point rather than a razor sharp edge. The cutting edge is thicker and will wear off more slowly.

For the past 5 years I've been mowing with a JD 2210 MMM. I bought it used with 100hrs on the clock. The blades were sharp. I mowed all that Summer without touching them. The next Spring I took the blades off to sharpen them. I then realized they are hardened. They had some nicks but were still relatively sharp. I put them back on without doing anything to them. I ran them for the next 3 years never sharpening them. I replaced them last Winter when I inspected them and noticed they were wearing thin where the blade curves up at the back edge to create lift. Eventually the raised edge was going to break off. I don't know what they make those blades out of, but sharpening is a thing of the past for me now. I mow 4 acres.

On my brushcutters the cutting edge is blunt. I never sharpen them. My little 6' Rhino leaves a very well cut look. Not lawn quality, but close. And that's with a blade that you couldn't cut yourself with if you tried.

 

[ovrszd]

Most grass is cut with the last 1/16" of the blade tip.

And this is confirmed when you look at an old blade, the outer 1/2" of blade is always worn away more than the rest of the edge.

This is also why going too fast starts pushing the grass over and not cutting it properly. When your forward speed is faster than the outer end of the blade can make the circle and come back around to cut again without leaving a gap. You then begin to cut with the inner part of the blade and efficiency is lost.

 

[Kyle_in_Tex]

My current mowing setup is a 7 ft pull type Woods RD8400. Recently I put new blades on and the difference in the grass quality is amazing compared with the "before" blades. I mow at 3 1/2". The mower also doesn't clump the grass clippings any more either but distributes them evenly. I'm now sold on sharp blades.

I know to sharpen them when they are dull and need it but how often is that for most people? And do a given number of sharpenings mean you replace or do you just keep sharpening as long as there are no nicks in the blades? I hear everything from four times a season to every four years. What do others do?


Also, the owner's manuals say to not sharpen the blades to an edge but, in effect, leave them with a dull radius. Why? It doesn't sound right so it that advice just a liability issue?

First off, your tractor is way too clean.

I like to even have sharp bush hog blades, but not so easily kept up with. I have flint rocks that are up to large potato size. I try to pick them up, but they keep spawning. They take their toll on the blade's tip, rounding it off where you need it sharp.

Sharp blades cut through grass easier and save fuel. In Bahia grass, I have to slow down as it lugs down my 4310's 25 pto hp. Sharp blades help it cruise right on through.

 

[sixdogs]

Tractor not quite that clean. Date shown in photo is 4 years earlier.

But I do wash them either once a year or every other year and I am fundamentally (wife says) pretty sloppy otherwise. This tractor is a dedicated lawn mower. Used to be I used the 6' belly mower but the 7' rear blade does a better and faster job.

 

[JohnWhayne]

After Dinner......

 

[EddieWalker]

I tried sharpening the blades once. It worked find, but I found that they got dull really fast and when I took them off again to sharpen them, I changed my mind and just bought new ones. For the time and effort it takes to sharpen them, I've come to the conclusion that I'll just buy new ones every year.

I start out the season with last years blades, then when I have everything under control, buy new ones to keep everything nice for the rest of the year.

Eddie

 

[Kyle_in_Tex]

There is another thread about throwing a bush hog blade. Check your blade bolts carefully and replace them at signs of abnormal wear. You could easily kill or destroy something. I think a 6' blade weighs maybe 20 lbs?

I know it probably doesn't last long, but I apply a bit of high temp copper or titanium lube to the bolt journal. It might would help to polish the ID of a new blade's hole.

 

[C4Ranch]

Agree that sharp blades help reduce lugging and improve efficiency. I sharpen abt once a yr and cut 2acres around the house.

I balance the blade by hanging off a nail in a vice to make sure it hangs level.

 

[rswyan]

The blades on our 6' Kubota MMM came from the factory with a blunt edge 1/16" or so wide. I don't sharpen them any sharper than that because, as k0ua suggests, a very sharp blade will dull pretty quickly.

We probably mow about 4 acres every mowing with the Kubota (we have a smaller Simplicity that gets used to do the area around the house) Our mowing usually cycle varies between every 5 to every 10 days, depending on weather ... mainly how much rain we're getting.

Blades usually get rotated out at the start and the mid-point of the mowing season, although last year I ran a single set for the entire season.

I use a flap disc in an angle grinder to clean up the machined angle on the blade unless it's really chewed up and then I use a grinding disc ... and I'll leave any really bad nicks. I use a flat file to put the actual edge on the blade and keep it straight.

 

[Gary Fowler]

I have two sets of blades for each mower and change them about 3 times per season. I have lots of crawfish mounds that take a toll on the blades + the occasional rock that gets hit. I use my FEL to jack up the mower then my impact gun to remove the bolts. It takes maybe 10 minutes to complete the change out including time to get the tractor FEL chained up. I then sharpen up the spare set so it is ready for a swap out. I mow about 6 acres at a time normally about once per week but this year what with all the rain, it has been about every 4 days.

I sharpen them using a flapper wheel on my 4.5" grinder. I don't try to keep the end square as it tends to round up a bit, so I just sharpen to the blade contour out to the end. As said, all the cutting is on about 2" of the blade with most being right on the tip so not much to sharpen except on the last 2" of blade. The lift fin usually wears out before the rest of the blade. I have used weld metal to build up the transition zone where it starts to bend up as that is where they will wear thru at. This seems to work well using 6010 rod and the wear pretty much stops at that point. One does need to keep the weld metal the same on both ends so they stay balanced.

 

[Ed of all trades]

I have a commercial lawn mower blade sharpener. I sharpen for myself, I mow about 4 hr's a week, two neighbors that mow around the same and the other a lot more and a simi pro that has 8 or 10 yards, We all do it the same, the grass tells us when we need to sharpen. when the quality of cut starts to go down it is time to sharpen. I leave less than a 1/16 edge on the blade and if I get a spot sharp trying to get a dull place I dull it with a file. I sharpen my blades once or twice a year but could do it less if I would pick up sticks more often and did not mow along a state gravel road. I have run these blades for 5 years and expect to run them for another 4 or 5.

 

[sixdogs]

It's interesting that most people seem to use the abrasive flap disc rather than the grinding wheels of years ago.

 

[k0ua]

It's interesting that most people seem to use the abrasive flap disc rather than the grinding wheels of years ago.

You have much better control, It is much easier to maintain the angle, and it does not seem to heat up the blade.. A Win Win Win, situation.

 

[sixdogs]

You have much better control, It is much easier to maintain the angle, and it does not seem to heat up the blade.. A Win Win Win, situation.

Good thinking. I'm also going to get a backup set of blades or maybe just replace annually as EddieWalker suggests. These big blades are $125 a set, however and I can't find an aftermarket maker.

 

[Kyle_in_Tex]

It's interesting that most people seem to use the abrasive flap disc rather than the grinding wheels of years ago.

I actually mounted our bush hog 6' blades in a bridgeport type mill presenting the ground edge to the side edge of a 1/2" carbide endmill. I needed to remove a lot of metal. Moving the X and Z axis, they actually came out really good. Then I touched them up on the 6" wide belt sander with a 40 grit belt. 1/32 to 1/16 small flat on the edge.

 

[buckeyefarmer]

sharpen finish mower blades a couple times a yr on the bench grinder.