Go BottomSharpening blades on a mowing deck -- easy
 | BX23Fan
Join Date: May 2005 Posts: 25 Snohomish, WA 
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2006-05-30 130011
I have a 60" mowing deck for my BX-23, but haven't used it yet since my lawn is still a work in progress. This sucker is pretty heavy to lift/tilt by hand, which makes me wonder what the easiest way is to sharpen the blades. The manual says nothing about how to go about this. What's the easiest way to remove and sharpen the blades?
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| wingwiper
Join Date: Jun 2004 Posts: 676 
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2006-05-30 130013
I have a 60 inch as well and I made a pyramid stand out of 2 x 4 s and I push the back of the deck up to the stand and at the base is a shelf, I life the deck up onto the shelf and then tilt the entire deck against the stand. It holds it and prevens the deck from falling. I can clean, remove and sharpen blades do whatever and then it is just lower the front of the deck back onto the ground and then life the back of the deckoff of the shelf and I am done. ....
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 | DennisCTB
Join Date: Nov 1998 Posts: 2707 NorthWest NJ 
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2006-05-30 130014
I use the storage stands from Larry' mower axle. See the TP review in the link below. Great winter storage idea and makes maintenance easy. I only sharpen blades annually though.
Check the TP archives, we have had many other approaches to blade sharpening as well. ....
Link: Larry MowerAxle Review
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 | kthompson
Join Date: Oct 2005 Posts: 5275 South Carolina
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2006-05-30 130015
BX fan,
I have used ramps for autos but for my ztr found the hyd sissor jack the best option to access the blades.
GD, GB ....
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Add PhotoSharpening blades on a mowing deck -- easy
 | Murf
Join Date: Dec 1999 Posts: 7249 Toronto Area, Ontario, Canada
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2006-05-30 130031
As long as you're limber enough to get down on the floor alright, a MMM generally has enough lift height to get the deck up off the ground more than enough to spin the blades off.
Dismounting the deck just to sharpen is a lot of work, but if you have to take it off anyways that's a different story.
Best of luck. ....
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 | AnnBrush
Join Date: Mar 2004 Posts: 463 Troy OH
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2006-05-30 130037
How do y'all sharpen blades, any truth to the don't heat the blade using a grinder deal (tempering and all that). Who uses a file anyway? ....
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Add PhotoSharpening blades on a mowing deck -- easy
| kthompson
Join Date: Oct 2005 Posts: 5275 South Carolina
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2006-05-30 130039
AnnBush,
I use a 4 1/2 inch hand held grinder with the grinder wheel at the angle of the sharpen edge. It leaves it smoother that using the edge of any size wheel for me.
I have a 6 inch belt sander with proper belt it does the best job.
Neither gets the blade very hot, but I don't run blades until they are rounded either.
GD, GB ....
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| kthompson
Join Date: Oct 2005 Posts: 5275 South Carolina
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2006-05-30 130041
Murf,
"As long as you're limber enough to get down on the floor alright"
Amazing isn't it how far the floor can move to. There there is getting back up part. Also remembering all tools you will need while there and then all the jobs you need to do while there. ....
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Add PhotoSharpening blades on a mowing deck -- easy
| Murf
Join Date: Dec 1999 Posts: 7249 Toronto Area, Ontario, Canada
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2006-05-30 130042
There is some truth to the theory that overheating will change the temper of the metal, however, you also have to bear in mind what it is this material is doing also.
It's not brain surgery we're performing with this edge.
Having said that, and the fact that we sharpen a LOT of blades, both rotary and reels, we use a water cooled grinder (the bottom of the grinding wheel runs through a water bath like a tile saw), however the other big bonus to that is there is little if any dust or mess either.
The reality of the physics puts it in better perspective, the blades spin at the same speed as the motor, about 3,000 rpm. Since an average size for a blade is say 20" that is about a 63" circle, 3,000 times a minute or 189,000" per minute.
So the tip is moving about 3,150" or 262'6" a second.
At that speed nearly anything sharper than a Lousville Slugger will cut just fine!
Best of luck. ....
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Add PhotoSharpening blades on a mowing deck -- easy
| kthompson
Join Date: Oct 2005 Posts: 5275 South Carolina
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2006-05-30 130043
Murf,
Since an average size for a blade is say 20" that is about a 63" circle, 3,000 times a minute or 189,000" per minute.
How do you go from the 20" blade to the 63" circle? Does not a blade cut a circle the same diameter as it's length?
On the tip speed, you hit right what Bushhog says my RFM is running.
....
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Add PhotoSharpening blades on a mowing deck -- easy
| wingwiper
Join Date: Jun 2004 Posts: 676
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2006-05-30 130044
KT
20" is the Radius and not the Diameter and the circumference is the radius times pie or 3.14 which would give you 62.8".
Just thought I would jump in and give a hand.......smile ....
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Add PhotoSharpening blades on a mowing deck -- easy
| wingwiper
Join Date: Jun 2004 Posts: 676
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2006-05-30 130045
KT
20" is the Radius and not the Diameter and the circumference is the radius times pie or 3.14 which would give you 62.8".
Just thought I would jump in and give a hand.......smile ....
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 | AV8R
Join Date: Oct 2003 Posts: 882 North Central Wisconsin 
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2006-05-30 130048
Changing the temper of the steel:
I doubt that there is enough carbon in this steel to change the temper by grinding. This will only happen on a high carbon steel. Judging by how soft my blades are/were they are made from mild or low carbon steel (1018 or similar).
Just my $.02 ... ....
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 | Iowafun
Join Date: Jul 2004 Posts: 955 Central Iowa
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2006-05-30 130050
As long as you aren't hogging on the blade hard with a grinder you won't put tons of heat in them. But then I also wouldn't grab the fresh ground area with bare skin right after grinding. It will be hot to touch, but not hot enough to affect temper.
The main thing is to try to take roughly equal amounts of material off each side of the blade so the balance remains about the same. I've heard of some guys on this board using a hanger or nail in the bolt hole to check for balance.
I need to sharpen my MMM blades. They get dull when you run over lots of gopher mounds. Sigh... just something else that needs doing. ....
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 | DRankin
Join Date: Jan 2000 Posts: 5116 Northern Nevada
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2006-05-30 130052
The manual for my new Woods RFM says the blades should not be sharpened to a knife or razor type edge.
Instead, it says the blades will function best with a 1/64th squared off leading edge.
As far as the method..... I experimented for several years with the blades on my push mowers. When I sharpened as Murph described with a water bath grinder or a file the blades stayed sharper, longer.
When I used a bench grinder they not only dulled quicker, but chipped easier on the cutting edge.
I am not a metallurgist, but I think the red hot heat from the bench grinder makes the metal more brittle. I fooled around with annealing and case hardening the blade after sharpening but it still didn't do better than the cooler methods of sharpening.
....
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Add PhotoSharpening blades on a mowing deck -- easy
| kthompson
Join Date: Oct 2005 Posts: 5275 South Carolina
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2006-05-30 130055
WW and Murf,
Okay read WW reply: I did not read Murf's post to mean the circumference. I thought the Canadians had a way sneaky way to extend blades.
Thanks WW.
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 | Chief
Join Date: Jul 2003 Posts: 4297 Southwest MiddleTennessee
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2006-05-30 130057
I use a hand file. I found the largest single cut flat file the hardware carried and purchased a couple. I remove the blades and inspect the spindles and scrap off the old grass clippings. You can pressure wash if you like. It is a very SLOW process which takes me about 4 hours to sharpen 3 blades back to the original contour. In my opinion, I think the temper of the blade gets compromised with an electric grinder as it builds up so much heat; even with quenching in water after each pass. The blade sharpness seems to hold up much better if sharpened with a hand file in my experience. I have tried it both ways and the hand files seems to work best for me. It is a royal pain in the butt as it takes so long but works well. Don't forget the check the balance of each blade after you are done sharpening. ....
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Add PhotoSharpening blades on a mowing deck -- easy
| Murf
Join Date: Dec 1999 Posts: 7249 Toronto Area, Ontario, Canada
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2006-05-30 130058
I asked a friend of mine who is a metalurgical process engineeer just now this very question.
It seems that BOTH of AV8R's and DRankin's answers were right!! But not necessarily for the right reasons.
The metal is low carbon (mild) steel, and grinding will NOT make enough heat, or hold it for long enough to affect the temper.
However, the combination of cheap low cabon steel, and the rapid heating and cooling caused by grinding on such a small (thin) section of metal will cause extremely weak spots to occur, sort of like cracks in the structure, running from the front (cutting) edge to the rear.
This is what causes the symptoms DRankin mentioned in his post, about the chipping, and the overall shorter life of the edge.
We learned something today!!
Best of luck. ....
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| kthompson
Join Date: Oct 2005 Posts: 5275 South Carolina
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2006-05-30 130059
The success of a file over a grinder I don't beleive is due to the difference in tempature. I think it has to do with the fact you are sharpening the total angle of the edge. By taking a small hand held grinder I am able to lay the wheel on it the same as a file and it give very good results. I find my edge holds up about the same as the factory edge. This for me is impossible with a bench grinder.
I think you will find the factory edge is often cut with milling machine. Could be flooded with cutting fluid or not while being milled.
Murf, how does your friend sharpen his blades?
I found out yesterday Oregon is a large manf of replacement blades. Went to their web site and they give very good instructions on how to sharpen chain saw chains and how to break them in and such but I failed to find anything on lawnmower blades. Which I took to mean either they don't know or they assume we all know how to sharpen a blade. ....
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| DenisS
Join Date: May 2006 Posts: 367 NJ
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2006-05-30 130060
I don't know how much Kubota charges for their MMM blades, but I used to pay $7.99 for a John Deer blade at the Home Depot. My take on this is, it's easier to sharpen these blades any which way you want and get new ones when the old ones get wear out in a couple of years. ....
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Add PhotoSharpening blades on a mowing deck -- easy
| wingwiper
Join Date: Jun 2004 Posts: 676
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2006-05-30 130063
Murf & KT
It has been on my mind since this morning. The equation C = pie * R did not seem right. I just looked it up to refresh my mind and it turns out to be C = D * pie so instead of 62.8 feet it should be 125.6 feet. Just for GP
....
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Add PhotoSharpening blades on a mowing deck -- easy
| wingwiper
Join Date: Jun 2004 Posts: 676
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2006-05-30 130066
Whoops! again... change the feet to inches. ....
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Add PhotoSharpening blades on a mowing deck -- easy
 | Peters
Join Date: Feb 2002 Posts: 3034 Northern AL
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2006-05-30 130078
WW you were right the first time. It is two pie radius or pie times the diameter.
The temper and steel on the mowers vary. The blades on the Bulher are quite hard I would think harden D2 as I have real problems grinding them. I have only sharpened them once. They hold the edge well. I would not want to guess how long they would take to file. ....
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Add PhotoSharpening blades on a mowing deck -- easy
| Murf
Join Date: Dec 1999 Posts: 7249 Toronto Area, Ontario, Canada
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2006-05-30 130081
WW, another reason I don't 'practice' as an engineer, I'm out of practice!!!
Kenneth, he doesn't, he brings them to me!!!!
Best of luck. ....
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