lawn mower blade problem

[LMan1967]

On my ZTR, its got three blades. I mow about 5 acres with it...not putting-green smooth grass, but not wilderness, either. I stick to the grass.

Last year, my wife came and told me that she accidentally hit a piece of metal in the yard while mowing. I look at the blades and sure enough, the back (hi lift area or whatever) area on all three is blown out/broken off, and the front edges are...not edges any more. Blunt as a butter knife.


So I put on three new blades, and both of us have been real careful about picking up the sticks, hitting nothing but grass, etc. a week ago I go to sharpen the blades. two of the three look EXACTLY like the old set did...the back of the blades is blown out/missing, no edges any more, completely ruined. :confused2: Weve hit nothing worse than a pine cone!

Whats going on? I can rem using a push mower for decades on a suburban yard, hitting all kinds of things, and NEVER actually seeing 1/4 of the blade missing! Why am I going through blades like this? :confused3:

 

[toppop52]

Sand, small sticks and pebbles, but especially sand, will eat blades and dull them like a brick.

 

[LMan1967]

Yeah someone suggested to me it was hitting anthills. Dont think that would break off the backside of the blades, though...:confused3:

 

[toppop52]

All three of mine were ruined, 2 had the lifts broken off, all were brand new in April, nothing but sand and small sticks.

 

[woodchuckie]

Sand will wear away the blade in a hurry. End, front and back.

 

[LD1]

Any pictures?? I cant visualize what you actually mean by "backside broken off"

IE: are they actually broken?? or just worn down?

 

[LMan1967]

All three of mine were ruined, 2 had the lifts broken off, all were brand new in April, nothing but sand and small sticks.

This....the lifts are broken off. Thanks, I didnt know that's what they are called

At least its not just me, although my problem remains :laughing:


I wasnt counting on having to replace all the blades 2x a season...this is an unpleasant development!

 

[LD1]

Are they actually broken?? or just worn down??(or worn so thin that they THEN broke?)

 

[DonnieP]

I've mowed a lot of grass in the past half century, starting with reel mower, 1 push mowers, 2 ride on's and the past three years have had a ztr. I have never replaced a blade until this ztr, sharpened them enough, but never replaced. I'm on the third set now. I feel your pain.
Donnie

 

[LMan1967]

Are they actually broken?? or just worn down??(or worn so thin that they THEN broke?)

Ill take a pic and post it when I get a chance. They are broken.

Im thinking it may be the high RPMs. A push mower runs, what, 3600 RPM? I know ZTR blades turn a lot faster.

 

[RandyT]

I will try to explain what is going on. When you mower you pick up debris, IE, dust, sand, rocks. The air flowing over the air lift tends to get more dirt abrasion right where the blade is bent to create the lift. this sandblasting slowly cuts the blade at that point, until it basically cuts the air lifts off the blade. Blades from years ago didn't seem to have this problem like todays blades, so I don't know if they are just softer, or a different material.

 

[Dapolksjj]

I will try to explain what is going on. When you mower you pick up debris, IE, dust, sand, rocks. The air flowing over the air lift tends to get more dirt abrasion right where the blade is bent to create the lift. this sandblasting slowly cuts the blade at that point, until it basically cuts the air lifts off the blade. Blades from years ago didn't seem to have this problem like todays blades, so I don't know if they are just softer, or a different material.

Can a hard surface be welded on to the backs of these blades to cut down the erosion?

 

[LD1]

I dont think ZTR blades really spin much faster than a pushmower @ 3600.

Most tout a blade-tip speed in the 19,000 fpm range. Thats 228,000 inches per minute.

An average 60" deck will have 20" blades. 20" times pi (3.14) is 62.8" circumfrence

228,000 IPM / 62.8" = only 3630 RPM

Another way to look at it....compair the size of the spindle pulleys to the motor pulley. For the blades to spin faster than the motor, the spindle pulleys have to be smaller than the motor(drive) pulley. Most are the same (or close) sizes.

RandyT explains what is going on pretty well. But it usually dont happen in only one season unless it is REALLY sandy OR you are mowing ALOT.

Thicker blades will help too as will a milder blade. (NOT a high-lift).

 

[LMan1967]

Thanks for the info. I'll look for a lower lift blade then.

I cant do anything about the sandy soil or how much I mow, but its not alot....I only avg about 25-30 hours a season on the clock.

 

[jinman]

I replace blades at least once per year on my regular use mower with 48" deck. The lift fins will be completely eroded away or paper thin from the sand erosion. Perhaps if you have a dense cover like St. Augustine, the sand will not erode the blades, but in my Bermuda grass/mixed grass lawn the sand can come right through and just tears up the blades in a very short time. I consider blades a consumable just like gas and oil.

 

[toppop52]

Blades don't last the way they use to, I don't know if it's inferior metal, higher speeds or what, I use to get 2-3 years with sharpening easily, now I rarely even sharpen them. By the time they dull they're worthless.

 

[bigtiller]

Wow, I did not know sand would do this to mower blades. I have never had to replace a worn out blade, but I don't have any sand either.

 

[JDgreen227]

Blades don't last the way they use to, I don't know if it's inferior metal, higher speeds or what, I use to get 2-3 years with sharpening easily, now I rarely even sharpen them. By the time they dull they're worthless.

The OEM 7-Iron deck blades on my Deere lasted 8 mowing seasons (about 75 mowing hours per season) with only minor touch ups to the cutting edges every year and when I replaced them with Gator blades two years ago they (OEM) were still reasonably decent and could have been resharpened and used. Much of the 5 acres of yard here are rough weeds and my ATV trails that I cut are full of grapevines, etc. but after 2 years the Gator blades still look almost new and there is no erosion anyplace. LMan1967 says he only goes 25-30 hours a season...I am amazed any blade can be that worn down so quickly but I don't have any sand.

 

[toppop52]

The OEM 7-Iron deck blades on my Deere lasted 8 mowing seasons (about 75 mowing hours per season) with only minor touch ups to the cutting edges every year and when I replaced them with Gator blades two years ago they (OEM) were still reasonably decent and could have been resharpened and used. Much of the 5 acres of yard here are rough weeds and my ATV trails that I cut are full of grapevines, etc. but after 2 years the Gator blades still look almost new and there is no erosion anyplace. LMan1967 says he only goes 25-30 hours a season...I am amazed any blade can be that worn down so quickly but I don't have any sand.

It's the sand, no doubt, when I got property with a high content of sand my blades went to hel!!

 

[JDgreen227]

It's the sand, no doubt, when I got property with a high content of sand my blades went to hel!!

Have to wonder if mowing right after a rainfall or after the yard being sprinkled would cut down on the amount of sand being lifted?