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Thread: OT - sharpening push reel mower with lapping compound - what grit?

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    richard newman is offline Stainless
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    Default OT - sharpening push reel mower with lapping compound - what grit?

    The old lady says its time to sharpen the push mower NOW! I saw youtube videos using lapping compound, wondering what grit to use? Could order a kit, but it seems unnecessary, and can't wait for it arrive.

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    gvasale is offline Hot Rolled
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    I used automotive valve grinding compound the last time I did it. medium grit worked ok, but if you want to do it twice & then use a finer grit, that would work too.

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    TGTool is offline Cast Iron
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    Not sure what videos you watched. 240 grit (medium) works fine. Don't forget you're rotating the reel backwards so you don't round off the cutting edges. You can look at the reel and the bedknife wear pattern now and see what condition they're in. If the reel blades are worn completely cylindrical you're not going to get much from lapping. You want a small land and a relief just like a primary and secondary on a milling cutter on the reel blade and just a small land on the bedknife for the best cutting action without undue effort.

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    Pikle Faktory is offline Plastic
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    A long time ago I was directed on grinding the reels and bed knives for a golf course gang mower set, and I remember taking some of the lapping conpound for valve grinding compound --it was in between the 320 and 180 that I had, these were iron wheel mowers fron the20s, first the bed knives were ground flat across the length, then a relief, and the reels were set on a fixture and ground so the contact area was small-relief angle-then to a cylinder shape (round) a tool was installed to turn the reel backwards to lap the reel to the bed knife with compound -after they were ground--properly adjusted they took almost no effort to pull, the contact area had to pass a piece of newspaper flat without cutting it, yet when presented 90 degrees to the blade contact cut it cleanly. ---at one time I was offered the sharpening machine, the old mad had died, I was the only person that knew how to use it, but I had no place to keep it and wasn't interested in sharpening reels then.
    JoeE. likes this.

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    Forrest Addy is online now Diamond
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    I could care less about lawns and lawn mowers. Landscaping is the world's boggest bor so far as I'm concerned but I do admire a handsome green healthy lawn especially under my bare feet.

    Yeah. lapping a lawn mower reel to its bar is a quick and dirty fix if casually done without thought. It works but the effect is to make a cylindrical surface on the reel blades. They won't cut cleanly. They pinch the grass blade off bruising the tissue of living plants. The cells die back and 1/16 to 1/4" of the cut end turns brown depending on weather and water stress. The cut has to be clean inthe grass blades are to heal properly.

    You have to remember a reel lawmower rotor is like a milling cutter The edge has a radial clearance otherwise the grass blade will be pulped not sheared. The result is a zillion little brown ends sticking up. I can see lapping as a final matching operation but not as a means re-sharpening a reel from dull to like new condition. You need a purpose built reel grinding machine for that - or a well enginnered home built reel joining grinder; you have to establish concentricity, remove nicks, and set the radial clearance before any touch-up and refinement is attemped.

    If you value the appearance of your lawn and the weather is warm, pay the money and get it sharpened right. OTH, try it. Report back.

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    Thanks a bunch for the information in this thread! I need to sharpen my Locke triplex soon. Probably should get some of the stones out of the lawn too...

    Actually have two to do. One I use alot, and another that is Rusty! and will need lots of grinding. On the reel grinding machines, do they use a finger like the endmill grinders do to turn the reel as it is sharpened? Anyone have a picture of such a machine?

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    adama is online now Diamond
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    I just sharpen mine by pulling it apart, Real goes in the lathe and a light skim is taken, such that any burr is left on the back of the cutting edge. Bottom blade - anvil gets a quick ride on the surface grinder.

    For your own personal use, don't bother trying to remove every nick, just remove the worst, you will never notice the effect in cut quality of perfect blades versus the odd slight nick.

    As for pushing the thing up and down the lawn. its a cheap gym member ship for a fat SWMBO :-)

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    adama is online now Diamond
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    As to reliveing the cutting edge on the cylinder why? Grass is not a solid block of metal it will happily push away as cut.

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    crossthread is offline Stainless
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    Way back when I was pushing one of these I found you could do a half way (or at least quick) job of touching up the blades with one of those hand ice skate sharpeners. It consisted of a cylindrical stone about three inches long and 3/8" diameter mounted in a holder/guide that you would slide back and forth on the ice skate to put a concave, razor sharp edge on the blade. I tried it on my lawn mower just for grins and it did a very passable job and only took about 10 minutes.

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    crossthread's Avatar
    crossthread is offline Stainless
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    Limy Sami is online now Diamond
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    When dealing with grass, if a rotary or flail mower ain't good enough, this fixes it.


    Roundup Weedkiller, the best weed killer for gardens: get rid of garden weeds!

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    Ray Behner is online now Titanium
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    My brother has a Fate, Root & Heath grinder for the reels and bed knives. With the proper relief on both, the clippings don't stay on the bed knife and you get a much better shear effect, leaving a clean cut lawn. Not much different than an endmill.

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    TGTool is offline Cast Iron
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    RE: Reel Grinding. When I worked for a turf outfit way back when and we sold Jacobsen equipment, they also had the Worthington line of pull behind reel mowers, the kind you'd see gangs of behind a tractor. Jacobsen taught that there were two methods or reel grinding. At the factory they did a cylindrical grind, just like a cylindrical grinder, followed by a relief leaving a small land. This was a good production method and lasted longer perhaps without adjustment. The method used mostly in the field was to grind the relief first all the way up to the front edge, then grind the primary afterwards. It had a smaller angle but didn't leave a cylindrical land per se. It was a sharper cut but would require a bedknife adjustment sooner. They could be sent out that way and for gang mowers generally were. Greens mowers usually got the hone job after grinding. And yes, there is a follower finger rest just like end mill flute sharpening.

    Grinding reels and bedknives is a noisy, dusty, ugly job. I was glad to know how, but glad to move on to something else.

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    gvasale is offline Hot Rolled
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    I've got both machines, reel sharpener, & bed knife grinder. I've looked for a long time for directions on how to use them.

    Still looking...

    Fate Root Heath...Ideal...

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    HuFlungDung is online now Diamond
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    Would it be the case that the 'bed knife' is the one that takes the most wear and needs addressing first? No amount of lapping is really going to fix that in the direction that it needs to be fixed in. Lapping will only serve to increase the gap, and won't square up the edge.

  16. #16
    gvasale is offline Hot Rolled
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    That gap is adjustable until you run out of adjustment. I suspect a thicker bed knife will make it work for a while.

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