Mower Blade Flap Discs

[Wamsutta]

You guys prefer the Type 27 or Type 29 when sharpening your mower blades?

And if you don't mind, can you tell me whether you prefer 40, 60, 80, or 120 grit?

 

[d.mcfarland]

I've used both without issue and the 80 or 120 grit would be plenty. No need to hog away that much material.

Ideally you'll want to sharpen every handful of mows if you have sandy soil, a large yard, and/or hit something.

 

[Beerhippie]

I use the flat style--T27. 80 grit, but I put a final, slightly steeper, edge on with a single-cut ******* file.

I only use the flap disk when the blade needs serious work, and give it touch-up with the file after every round of mowing. Old riverbed--and feral children hiding rocks in the grass--is hard on blades.

If you want a hollow-grind to the edge, just hold the disk so it cuts on its edge instead of flat to the blade.

 

[BTL-A4]

I find that power tools sometimes are too aggressive, so I use a hand file for mower blades. A smooth one works well. It takes longer, but you have more control. I balance the blade on a nail in the wall after I sharpen it and make sure it's level so I know both sides are even to keep the blade balanced.

 

[Steve_P]

80 grit T27 style. I do mine once a year after the season ends.

 

[Wamsutta]

You guys are fantastic. Thanks for all the replies.

 

[dnschmidt]

I don't have any grass so I don't know anything about sharpening lawn mower blades but I know a lot about flap discs. Either type will work fine but I generally prefer 60 grit for everything from weld removal to whatever. Oddly, if you watch "JIMBO'S GARAGE" on YouTube he's a fan of 60 grit as well. The 80 and 120 grit wheels tend to load fairly fast and they tend to overheat the work. I've never had a problem with 60 grit. Another point: Flap discs should be used at about 5,000 to 8,000 RPM so a variable speed grinder is highly advisable. Check out the flap disc section of the following technical article: https://www.lehighvalleyabrasives.com/content/developments-in-abrasives.html

 

[Beerhippie]

I don't have any grass so I don't know anything about sharpening lawn mower blades but I know a lot about flap discs. Either type will work fine but I generally prefer 60 grit for everything from weld removal to whatever. Oddly, if you watch "JIMBO'S GARAGE" on YouTube he's a fan of 60 grit as well. The 80 and 120 grit wheels tend to load fairly fast and they tend to overheat the work. I've never had a problem with 60 grit. Another point: Flap discs should be used at about 5,000 to 8,000 RPM so a variable speed grinder is highly advisable. Check out the flap disc section of the following technical article: https://www.lehighvalleyabrasives.com/content/developments-in-abrasives.html

The trick to keeping a flap disk from "burning" the blade--overheating it--is simply to keep it moving with light pressure on it--like no more than the weight of the grinder.l

I've never burned a mower blade using a flap wheel. A solid stone disk is another matter altogether.

For heavy metal removal--cleaning up welds, shaping, etc--I go with 36 grit Cubitron II on a 5" fiber disk. I've never seen anything cut so fast.

 

[seber]

I agree with the 60 grit advice. I have no problem with the finish it gives on mower blades. In addition to working faster with no build up, it avoids heating the steel.