Rotary Cutter Sharpening rotary cutter blades.

[N80]

I looked under my used, but new to me, JD LX6 rotary cutter. Everything looks great except for the blade edges, which look terrible. I know they're not supposed to look like Ginsu knives but they a dull and dinged with some indentions.

So I'd like to sharpen them. I have a big new file that I sharpen axes with by hand, but I have access to a larger bench grinder and a pneumatic handheld grinder.

I just don't know how to get to them. The manual (online, I don't have a hard copy) shows accessig the nut through a hole in the deck but they show some sort of tool that I don't recognize (torque multiplier). Do you have to have this tool to get the blades off?

The manual also says to discard the mounting hardware but doesn't say specifically what that means or why it must be discarded. Is it just a nut and bolt or a bushing? Do I discard it only if I'm putting new blades on, or do I discard them if putting the same blades back on?

My brother-in-law recommended, in passing, that I could use his pneumatic grinder to sharpen them on the mower. But how would you get access to them? The tractor doesn't really lift it high enough to work underneath it. I guess maybe i could tighten the top link way down to get a little more lift and then put jackstands under it, but even then it would be a little cramped for running a grinder. Any ideas.

Finally, how do you know when to replace the blades. They are nicked and dinged but they are not bent and there are no chuncks of blade missing.

Thanks for any pointers you can throw my way.

 

[Highbeam]

I have a similar situation but it is just because I have worn them down. When new, these blades have about a 45 degree grind down to a 1/8" thick edge. Not very sharp. After using them, the 1/2" thick blade looks pretty much like a frisbee edge and would take lots of grinding to get back to that 45/0.125 setting. Then the very ends of the blades farthest from the center wear much faster so they are rounded off in two directions. I have even considered adding beads of weld to make an edge since it would be quicker than grinding and would be adding metal rather than removing it.

I have yet to remove the blades and don't think I will want or need to. You can disconnect the top link and pto, then somehow raise the tail of the mower high enough to get in there. The tool of choice for grinding is a 4.5 inch right angle grinder from walmart for less than 30$, great tool and there's enough room to get in there with it. Ear plugs and glasses.

Why sharpen? The blades do a fantastic job even when shaped like a frisbee. With heavy grass a sharp blade will do the job easier and look better but for field mowing I have found the weed wacker effect to be sufficient.

The large blade retaining nuts are high torque items and I suspect the part you are suppsoed to discard is the cotter pin.

 

[Bird]

I've never really looked at an LX6, but I'll assume it's similar to a Bush Hog with the hole in the deck to access the nuts that hold the blades on. They are torqued very tight; probably 400 to 600 ft. lbs.. I never had any problem removing them with an air impact wrench that produced 425 ft. lbs., but otherwise you may need a long break over or "cheater" bar. I know there are some products that recommend discarding used nuts and bolts and replacing with new ones, but I'm not sure how many people actually do that. So if you don't remove them, and instead sharpen them on the mower, some people unhook the mower from the tractor and use either the tractor's front end loader, or a block and tackle in a tree, to raise it up on its side so they can easily get to the blades. Also remember that you don't normally sharpen those blades as sharp as you would a lawn mower. Bush Hog recommends a 1/8" flat edge to prevent or at least slow the number of "nicks" you get in the edge. Of course if you're only going to be mowing grass, no woody material, you might want them a little sharper. As for when you replace them, some never sharpen them; just replace them. Personally, if I couldn't find any cracks, bends, etc., I'd probably just sharpen them.

 

[RalphVa]

Try doing a search on this. There have been tons of posts on it in the past.

I have an LX4 and have yet to do the sharpening. Bought a Farmhand 1/2" drive impact wrench that is good for up to 550 ft-lb that I hope will take the bolts loose. Hoping to take it back a couple stops on the control for retightening. I bought a nifty little compressor that's good for 5 scfm that powers it fine in other uses I've used the impact wrench for so far. It's a little oil-type Clark. Bought the Farmhand impact wrench and the Clark at TSC. Had to go down the street to a heavy duty tool place to buy the impact sockets though. However, I bought the heavy 1 1/2" socket for the bolt on the brush hog blades somewhere else, maybe Sears. Good idea to buy special impact sockets and 6 pointers. DO NOT use multipointed sockets for heavy impact work.

I used a "cheater" bar that I made by just clamping a piece of pipe to my big 3/4" drive with a couple heater hoses to get the 3 ph nuts loose and back tight. They're supposed to be torqued to 450 ft-lb, too. Worked. Don't think the torque is so critical that you need to actually use a torque wrench.

Search on the internet for torque wrenches. You'll find the double type and even find instructions on how to make your own from a bar with drive on one end and socket on the other end with your standard torque wrench going into the socket. There's a name for them that escapes me as I'm typing. Buying them off the shelf is high bucks. Don't need.

Ralph

 

[Highbeam]

My experience with bolts that are supposed to be torqued to 450 ft-lbs is that an impact wrench rated for 500 won't do it. Maybe they seize up with time or maybe the factory puts them on extra tight but they are not easy to remove.

Let us know how those buggers come off.

 

[N80]

Thanks for the advice guys. Like I say, I've got access to a pretty complete shop just down the road. It is starting to sound like just borrowing the angle grinder and leaving the blades in place might be easier.

I also remembered that he has an overhead hoist system. So, like someone said, remove the top link and PTO then hook the hoist to the tail wheel and cranking it up should give me enough room and be relatively safe.

I'll let you know how it comes out. He may have one of those torque multipliers things to, I'll check, but even so, leaving them in place is sounding better by the minute.

Thanks again.

 

[19977]

I thought about taking them off just to put never-seize on the nuts,so later on they'll be easier to get off.Is this a bad idea?
Thanks Mike

 

[Soundguy]

The 'correct' (bondage & discipline) way would be to drop the blades, and sharpen, ballance, and reinstall with new nuts and botls.

However.. every farmer and 99.9% of ever tractor owner that I have ever met.. simply lift / jack the mower, and take an angle grinder to it.

As other mentioned.. for brush cutting, a 1/8 flat is as sharp as you need to get. if yuo are going to clip grass for a shaggy lawn look, and will not encounter rocks / brush / burried obstacles.. you coult go down to an edge more like a lawnmower.

Try to grind nicks out a bit.. but not much.

A blade has plenty of 'wear' built in to it. Eventually the blade will round out on the leading edge, actually making the blade and cut width shrink. At this point.. replace them, as you are loosing cut width, and the tip of the blade is thinning... also.. bad chips and broken tips = blade replacement.

Always support the mower.. lumber / stands... chain..e tc.. don't rely on hyds...

Depending ont he discharge chute orientation.. you may be able to reach under thru the chute and sharpen the blades with only a foot or two of lift on the mower.

Soundguy

 

[Farmwithjunk]

What SoundGuy said..........

Good to see you made it through the heavy weather too!

 

[Highbeam]

Are these blades typically 10$ items or 100$ items? I can add material to the blades if the replacements are pricey.