Angle grinder for sharpening blades

Discussion in 'Mechanic and Repair' started by Roger, Jul 19, 2006.

  1. Roger

    Roger LawnSite Fanatic
    Messages: 5,940

    I bought an angle grinder about 10 days ago. Historically, I have sharpened blades with a hand file. A recent purchase of a ZTR with thicker blades makes the job more difficult with a file.

    My question for you who use an angle grinder (I know there are some because I checked threads before I bought mine): How do you hold the blades when grinding?

    I ask the question because I wanted to sharpen with the wheel turning TOWARD the cutting edge. However, after much rotating of the vise, changing the safety shield on the angle grinder, etc, I find the only way that seems to work is having the wheel rotating AWAY from the cutting edge.

    I have settled on the vise grips being parallel to the workbench, mounting the blade horizontally, flat. This leaves me with one cutting edge on one side of the vise, the other cutting edge on the other side of the vise. I have the handle on my angle grinder mounted on the left side of the unit. Grabbing the grinder in my left hand (with on/off switch within easy control), and my right hand on the extended handle, I can hold the grinder at an angle so that the wheel is flush with the sloping cutting surface of the blade. With a good light above, I can easily see where the wheel is cutting and make any adjustments. Moving the grinder back/forth, I can get the surface ground flat.

    I turn the blade, and do the other end the same way. Also, I now take a hand file to touch up the first end. And, turing the blade again, the file is used to touch up the second end.

    How do you use your angle grinder for sharpening? I'm looking for how you hold the blade in the vise, where you position yourself, how to align the grinder, etc. Or, is my configuration the best one?


    P.S. Save the suggestions about getting a blade grinder. I'm a small operator and don't have that many blades to sharpen (about 12 per week), and I don't want to spend $300 for something used so infrequently.
  2. Audrey

    Audrey LawnSite Senior Member
    from Pa.
    Messages: 570

    IMO, that would warrant a blade sharpener. If you were to take them to a dealer, you would easily pay for the machine in less than one season.

    I now use the grinder as opposed to the dealer sharpening them. What I do is use sanding discs instead of grinding wheels. I don't let the blades get to the point of where they need to be ground, but just touched up. If I hit a rock, stump, or small dog, and there's a chunk taken out, I will then use the wheel as opposed to the disc.

    Using a sanding disc eliminates the heavy downward pressure you need to apply. This makes it easier to hold. You can also change grits to remove more if you wish. I hold my blades flat in a large, heavy vise. Works like a charm. Just be easy with your method.

    If you have a decent bench grinder with some snot to it, you can do your blades there. If you have the feel in your hands you won't have any problems. Sometimes I'll rough them in there and finish with the sanding disc if i'm too lazy to change wheel grits.

    Anyone here ever try with a belt sander? Either a free hand one or one of the big ones on a stand. I thought of it the other day but didn't get to try it yet.

    I'm a tool wh0re and spend more than I should in that area, but I opted for the sander/grinder option also. But I did pick up a Magna Matic balancer. Good piece of equipment and I would recommend it. Save your money on the mounting bracket and make your own out of scrap wood. Just a big "L" is all you need.

  3. Let-it-mow!

    Let-it-mow! LawnSite Member
    Messages: 91

    We shapen with an angle grinder. We turn the vice 90ยบ so we are looking at the end of the blade and sharpen it that way. Flip the blade around and do the other edge.

    I don't care if the wheel is turning towards or away from the edge. When the wheel turns away from the cutting edge, it leaves a little rolled burr of metal at the cutting edge. But after 5 minutes of cutting, this burr is gone anyway.

    Althought I've never heard anyone say this, I suspect the grinder takes the temper out of the metal and softens the edge. We have a bucket of water next to the vice and quench the blade after each edge is ground.

    Somebody's going to post now that tempering needs to be done at very specific temperatures and at controlled rates of cooling and that quenching in water after grinding isn't the right way to do it. But I'm going to continue to do it that way anyway.

    The grinder doesn't do a pretty an edge as I'm sure a sander would but I don't think a blade needs to be polished, just sharp.
  4. ed2hess

    ed2hess LawnSite Fanatic
    Messages: 14,374

    I use angle grinder all the way. I have a little portable foldup table that is found at Home Depot. I clamp the blade to the table with a clamp. I put a sanding pad on top of a metal cut off wheel to give the pad some rigidity that the rubber backup don;'t provide. The sanding pad doesn't heat up the metal as much. I want sparks to fly up in the air and away and not down toward me so that determines grinding direction. As I have started the angle grinder can be used for the wavy mulch blades and hedge trimmers.
  5. Audrey

    Audrey LawnSite Senior Member
    from Pa.
    Messages: 570

    If the metal changes color, you have changed the hardness of the material being ground/sanded. It will never again hold an edge as it once did. 5 minutes of grinding? You must be cutting some nasty stuff!

    A sander will remove a decent amount of material depending on the grit you choose. Don't discount it because it's a "sander". We're not playing Norm Abrams here, it is not polishing the blade. What it is doing is helping to keep the temps down, and only removing the amount of material that is needed to redress the edge. The more material that is removed, the quicker you have to spring for a new blade. If I have a deep gouge I will use the grinder to take it out. Otherwise, I only remove the amount I need to.

  6. MLawns

    MLawns LawnSite Member
    Messages: 68

    I picked up a belt sander at an auction once just for blade sharpening and ended up giving it to my uncle for his woodshop. There just weren't enough RPM's and the edges were rounded....not a quality job. I know an industrial belt sander for a commercial use would do the trick so if you are going to go that route get a quality sander, and get one with plenty of RPM's. I don't remember the speed of the one I had but it wasn't fast enough. I am in the market for a blade grinder myself.
  7. Jim@MilkyWay

    Jim@MilkyWay LawnSite Senior Member
    Messages: 472

    I looked at that on the WWW a while back and immediately thought it looked like a good tool. What is it, like $50.
    I use a tuned up and very tricked out cheap cone balancer but will never be entirely happy with precise centering while using it.
    I also hollow grind my mower and even bush hog blades, plus I am a big fan of what I think is called the micro bevel.
    The master gardener course stated that cutting your grass is much friendlier to it than ripping it off. It also eases the load on your machine as a razor sharp blade virtually glides effortlessly through the cut job.
  8. oldrustycars

    oldrustycars LawnSite Senior Member
    Messages: 301

    if you're in business of mowing lawns, get a proper blade grinder, just my opinion. keeping the blades sharp, and at the original angle, makes everything easier on the mower, and does a better job of mowing. hand grinding can result in being off just a tiny amount each time, than after a year or so its way off, it adds up.
  9. Audrey

    Audrey LawnSite Senior Member
    from Pa.
    Messages: 570

  10. Jim@MilkyWay

    Jim@MilkyWay LawnSite Senior Member
    Messages: 472
    The magnetic balancer #3702716, part way down the page at this link is not the same item as you described, since it "appears" to still be a cone balancer. What do you think though; it should center the blade precisely. However, my statement about my el-cheapo being tricked out ....
    ....includes a modification to center blade about as well as possible for it.

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