Type Abrasive Wheel for Sharpening Flail Mower

[: JerryBowers]

I need to sharpen the flails on a 5' mower. They are not severely damaged, but are definitely not cutting as well as in the past.

I am planning to do it by disconnecting the mower from the tractor, rolling it over and sharpening with the flails still attached to the shaft, with perhaps a little support from clamps and some wood strips. I'll use my 4 1/2" grinder to do the work.

What type wheel should I use? Do I use a rigid carbide wheel, or some other wheel, like a sanding disk? What grit to start with? I am hoping to do this in one pass, but seeing as how the mower is about 5 years old, and the flails have never been sharpened, I don't mind spending a little extra time to make sure they will cut well for another 5 years.

All suggestions sincerely appreciated!

 

[john *.?-!.* cub owner]

Put a heavy leather glove on your left hand (assuming you are right handed), and hold a small 4 1/2 or 4 inch grinder in your right hand, one small enough you can handle it one handed. Type of wheel is not critical. Grab the shank of a pair of blades wiht gloved hand and run hand grinder over beveled edge of blade 2 to 4 passes. Do not try to get all the nicks out, you will just waste blade material, they will get nicked again. Remember, they only cut on one side, no use sharpening both sides, the back sides will just get beat yup again from hitting the other blades. My instructions are for this type blade, if yours are different you will need to improvise.

 

[Steve@Advance]

All you'll need are general purpose metal grinding discs. Try not to get the edge of the blades too hot. You'll get the feel of it, use heavy pressure until you get a decent edge, then lighten up for the finish. A big file works well to remove the roll over on the back side, and to fine dress it.

 

[Charles in Aus.]

I have had good results using an 4,1/2'' angle grinder flap wheel designed for stainless steel . Takes off a reasonable amount of material without being too aggressive and without the risk of bluing the metal . Leaves a polished surface as well as being a little easier on the wrists when using it one handed .

 

[MarkB_MI]

Just use a regular metal grinding disk. You can grab the knife with a Vise Grip.

It goes without saying that you can flip your knives over rather than sharpen them. And if both sides are worn, it may be easier to remove them and resharpen them on a bench grinder. And of course if they're seriously rounded off it may be time to replace them.

 

[showcrop]

I have been amazed at how much faster rubber backed discs are than the rigid ones. It must be more contact surface due to the flex.

 

[: JerryBowers]

Thanks for the information and suggestions!

I'm going to get a couple of the 4 1/2" Steel Demon Grinding & Polishing Flap Disks. They are available in 40, 60 & 80 grit, and are pretty affordable at ~$8 each. Since I don't really need or want to remove lots of metal, I think I'll start with a couple of the finer (80 grit) ones to see how it goes.

My flails are J-shaped, kind of like the tine on a tiller. I really appreciate the suggestion to use a vise grip to hold them.

The good news here is that they are not really worn, but just have somewhat rounded leading edges. Should be lots of room to sharpen them without coming close to end of life.

Going to be ~105 degrees here today, so I might not get very far on this project: Just go to the store and get the grinding disks and perhaps get the mower off the tractor.

I'll report back in a few days.

 

[GordoSD]

Email me your address and I'll send you a couple of 40 grit flap wheels I have a shoebox full.

 

[flhr62]

An air 90 grinder with cutting wheel works good

 

[showcrop]

(quoted from post at 10:04:44 06/15/15) An air 90 grinder with cutting wheel works good

sharpening is a grinding operation which should not be performed with a cut-off wheel as the cutoff wheel is not designed for the side load. It could fail injuring the user.

 

[flhr62]

Some of you guys are quite safe