When is a blade ready to change

[Mickwhitt 4,593]

Hi all.

Just wanted to ask your views on mower blade replacement. 

Obviously they are a wearing part and will need replacing after being sharpened so much.

But what makes a blade junk?

How much edge can be ground away before a blade needs to be scrapped.

The photo shows a blade from my John Deere deck with a brand new one for comparison.

The other blade is from a wheelhorse deck.

What do you guys think of the amount of metal left? Worth another sharpen or only good as a paper weight?

Mick 

[tunahead72 2,411]

Good question, I'll be interested in seeing what people think here. 

 

I usually keep a spare set or two around, so I don't have to rush a sharpening job while the yard needs to be mowed.  In close to 40 years, I've only actually tossed one set of badly worn blades that my trusted neighbor / Wheel Horse guy said were "sandblasted" and showing signs of cracks.  I usually sharpen my own blades, but I'm not very good at it, so every once in a while I'll take them somewhere to get them "professionally" sharpened.  I tend to trust their judgment about whether it's time to let them go, so far so good.

 

[lynnmor 7,302]

Due to the radius on the tips of the used ones, I would toss them.  If they were sharpened correctly the cutting edge would be all the way back to the bend.  I have seen thin blades, on throw-away big box mowers, that were worn completely thru at the bend leaving two fingers at each end waiting to become projectiles.

Edited September 5, 2020 by lynnmor

[Stormin 9,981]

  I'd sling them, Mick. And thanks for reminding me. I need a new set for my 42" rear discharge.

[peter lena 8,583]

good paper weights, the thing that killed those blades was improper sharpening , agree with above and toss them. i regularly use a small fine flat file on mine , minimising the metal loss ,and yet quickly recovering a sharp edge. when i see people just attacking a blade with a power grinder , you are destroying the blade . my blades are years old and still have a square ,sharp cutting edge. pete

[953 nut 55,099]

7 hours ago, Mickwhitt said:

what makes a blade junk?

They aren't junk, they can be used for dozens of projects around the shop, especially if a 3/4" hole in metal is needed.    Good for mowing,  not so much!

[Lee1977 6,648]

The real question is how good do you want it to mow. If you want the lawn to look great blade no. 1. If you are nocking down weeds on the back 40 blade no. 2. No. 3 is way past being good for anything.

[pfrederi 17,674]

#3 can be made into a spindle nut wrench (Cheaper than buying a Wheel Horse version)  Can also use it on the jam nut on sunstrand Motion controls.