Mower blade - how to repair suggestions

[dan_m]

I've got a few mower blades that are nicked and beat up from hitting various objects over the years. I've already replaced them but kept the old ones as you never know when you need a nice hunk of steel. I was thinking about ways I can repair them for more use. It seems the most common way I've been seeing is to clamp the blade vertical in a vise and grind the cutting edge off to the deepest nick and then re-add the cutting edge. In cases with deep nicks, I've got at least one that is about half way into the cutting edge due to a unseen rock. With this method, that's a lot of metal that will need to be removed - is it time to scrape that blade and repurpose? Even with a re-sharpen, there are still nicks and I'm not sure how much those will affect the quality of the cut but the blade just looks terrible and i am hesitant to put it back on.

Does anyone have any other suggestions for reviving old heavily nicked (not necessarily all with deep nicks but a lot of nicks along the entire cutting edge) blades?

I had a wild idea of using welder to fill the nicks and then grinding down and re-sharpening the blade. Has anyone ever tried this? would the extensive time and effort be worth it vs repurposing and purchasing a new blade? As an example, I see kubota blades for 60" deck are around $23 each on messicks (just to toss out a number).

Dan

 

[JerryMT]

I've got a few mower blades that are nicked and beat up from hitting various objects over the years. I've already replaced them but kept the old ones as you never know when you need a nice hunk of steel. I was thinking about ways I can repair them for more use. It seems the most common way I've been seeing is to clamp the blade vertical in a vise and grind the cutting edge off to the deepest nick and then re-add the cutting edge. In cases with deep nicks, I've got at least one that is about half way into the cutting edge due to a unseen rock. With this method, that's a lot of metal that will need to be removed - is it time to scrape that blade and repurpose? Even with a re-sharpen, there are still nicks and I'm not sure how much those will affect the quality of the cut but the blade just looks terrible and i am hesitant to put it back on.

Does anyone have any other suggestions for reviving old heavily nicked (not necessarily all with deep nicks but a lot of nicks along the entire cutting edge) blades?

I had a wild idea of using welder to fill the nicks and then grinding down and re-sharpening the blade. Has anyone ever tried this? would the extensive time and effort be worth it vs repurposing and purchasing a new blade? As an example, I see kubota blades for 60" deck are around $23 each on messicks (just to toss out a number).

Dan

I would not try to repair a badly damaged blade. The risk of an unseen crack propagating and causing an uncontained failure that can seriously hurt the user or a bystander is to great. Some mower manufacturers provide guidance on resharpening blades but I don't know of any that have repair procedures for severely damaged blades. Too risky for a manufacturer. Use the old blades to make a knife or a machete but don't put them on a piece of rotating machinery.

 

[RBsingl]

I agree with Jerry about the risk of using a severely damaged blade, especially once you start welding on it.

And unless you are really bored, the ratio of time spent to money saved trying to do major repair work versus the cost of new blades probably doesn't make much sense unless you are buying your new blades from the parts department of a BMW dealership

Rodger

 

[Mark_BX25D]

I hadn't thought of the crack aspect. That's food for thought.

I just wonder if it's even worth your time.

 

[skeets]

Ther are a lot of videos about using old blade to make a chopper out of,, but yeah plese dont try to weld them

 

[D2Cat]

I'd like to see a picture of the blades you consider nicked beyond sharpening. I'd never weld a mower blade, but a nick doesn't necessarily make it scrap.

When you say, "It seems the most common way I've been seeing is to clamp the blade vertical in a vise and grind the cutting edge off to the deepest nick and then re-add the cutting edge." is what causes me to wonder. I've sharpened MANY mower blades and I've never put one in a vice vertically to grind on it. Not saying it's wrong, but it indicates not much experience.

Mower blades are not sharpened to shave the hair on your arm. That edge is not required and if it is put on a mower blade it won't be sharp long. Show us a picture of what you're questioning.

 

[lugbolt]

I know that some mower blades are made of 1040 or 1045 steel. Not particularly hard, and not really crack prone. I've had some really dinged ones and just used a TIG to fill in the deep nicks, then reground them. Ain't never had a problem out of them but I've not hit anything with 'em after the repair is made either. At one point I made a set of blades--3 blade deck, I made it a 6 blade deck by welding 2 more blades 90 deg criss-cross. It also made the mass of spinning blades so heavy that the motor would barely turn them on; and then once on/running it took all 25hp to run them with no load. But they never broke, cracked, etc.

if you were to fill in the deep dings with a welder, I'd highly suggest tig welding and using ER70S-6 filler rod as it flows a little better than ER70S-2; making it easier to get that ding filled in. I haven't used any of this one blades, but 309L stainless filler will work well on dirt hot rolled steels, may also work on mower blades but it's a lot more expensive than ER70S-6. You'll have to grind away some material beforehand as TIG welding requires good clean base material; meaning you'll have to grind way back up into the vee of the ding. Once ground and cleaned, you can then fill it. When lighting up on it, hit it hard quick with lots of heat, and start dabbing filler into it quickly, to keep the heat affected zone to a minimum. Once you start moving your filler puddle toward the cutting edge, you're gonna have to back way off the heat because the material gets thinner and thinner. But it also gets wider, so you might have to make more than one pass to get it filled up. Then at the end of your job, run your puddle around in a circle as you ramp the heat down. This helps prevent a crater and helps to avoid a crack at the end of your weld. Then you get to grind, and finally balance. I like to paint them after the work is all done, but I don't weld them very often-only on my own stuff for testing purposes, and even that's rare..

I would not use any other welding process for this job, MIG MIGHT work but you have little control over the heat. Stick is out of the question.

Next issue if you have to grind much off of the cutting edge, you are effectively making the cutting diameter of the spinning blade a little smaller; thus affecting cut quality. Reason being, if you look at the blade tips, where the cuttin edge meets the very outside edge, it's not a 90 degree corner-it's more like 95-100 degrees. As you make the blade narrower by sharpening, it makes the blade cut width smaller. I notice it on my yard after about 2 sharpenings I start to see a difference. So I just replace them every other season and I'm due for it this season. I'll put another edge on them about Sept, then mulch up the pine needles and leaves to finish them off.

 

[RBsingl]

Agree with D2Cat that you aren't trying to go for razor blade sharpness. A decent bevel without major imperfections AND in balance after the edge is achieved are the critical objectives.

I rotate sets of blades for the deck on my Deere 955 and they go into scrap once they get enough hours and sharpening sessions on them. I start the season with the set that is currently the oldest/worst condition because I know the first mowing of the spring will be the toughest on the blades in terms of contacting things it shouldn't.

Lugbolt sounds like he definitely knows what he is doing with correcting blade imperfections via welding but with my level of skill, I wouldn't try it. It is sort of the same approach I used to take with Harbor Freight, I would take a chance on some seldom used hand and power tools from there but I wouldn't buy a carbide tipped saw blade or router bit from them. I just didn't trust the quality level with a piece of carbide spinning at high speed and maybe/maybe not brazed on properly. I would feel the same way about my blade welding ability.

Rodger

 

[dan_m]

I would not try to repair a badly damaged blade. The risk of an unseen crack propagating and causing an uncontained failure that can seriously hurt the user or a bystander is to great. Some mower manufacturers provide guidance on resharpening blades but I don't know of any that have repair procedures for severely damaged blades. Too risky for a manufacturer. Use the old blades to make a knife or a machete but don't put them on a piece of rotating machinery.

I wouldn't consider these badly damaged. Some are nicked in many places.

Dan

 

[dan_m]

I'd like to see a picture of the blades you consider nicked beyond sharpening. I'd never weld a mower blade, but a nick doesn't necessarily make it scrap.

When you say, "It seems the most common way I've been seeing is to clamp the blade vertical in a vise and grind the cutting edge off to the deepest nick and then re-add the cutting edge." is what causes me to wonder. I've sharpened MANY mower blades and I've never put one in a vice vertically to grind on it. Not saying it's wrong, but it indicates not much experience.

Mower blades are not sharpened to shave the hair on your arm. That edge is not required and if it is put on a mower blade it won't be sharp long. Show us a picture of what you're questioning.

Basically they grind off the cutting edge - grinding staight down on the edge to the deepest nick, then regrind a new cutting edge - in effect making the blade narrower.

Here's an example of the most common way I've see in researching (youtube + various forums).

Dan

 

[dan_m]

Here is an example of a "gently used blade" that has a couple bigger nicks (not bad in comparison) after it's already been resharpended. This is about as average of a damanged blade as I've got.


in this picture, you can see a couple bigger (longer, not really deep) nicks.

here is a view looking straight down on the cutting edge showing the nick (middle toward bottom of picture) and you can see it's not as narrow (sharp) as the inside (top of picture) of the cutting edge. I'm not sure how "terrible of a cut" this blade will leave. If I can improve the cut, I'd rather do that.

In this picture you can see how deep the nick is on the cutting edge. The blade is laying against level/straight edge. I'm guessing maybe 1/8" max, probably smaller.

Dan

 

[RBsingl]

For just nicks, grind a new edge. There is enough "meat" on the blade to clean it up a few times and once you have to take off too much material then it is time for a new blade.

When grinding out a lot of material, pause and let the blade cool a bit a few times during the process. Getting too aggressive with the grinder can heat it to the point where you have turned your factory heat treated blade into a brittle blade.

Rodger

 

[dan_m]

I know that some mower blades are made of 1040 or 1045 steel. Not particularly hard, and not really crack prone. I've had some really dinged ones and just used a TIG to fill in the deep nicks, then reground them. Ain't never had a problem out of them but I've not hit anything with 'em after the repair is made either. At one point I made a set of blades--3 blade deck, I made it a 6 blade deck by welding 2 more blades 90 deg criss-cross. It also made the mass of spinning blades so heavy that the motor would barely turn them on; and then once on/running it took all 25hp to run them with no load. But they never broke, cracked, etc.

if you were to fill in the deep dings with a welder, I'd highly suggest tig welding and using ER70S-6 filler rod as it flows a little better than ER70S-2; making it easier to get that ding filled in. I haven't used any of this one blades, but 309L stainless filler will work well on dirt hot rolled steels, may also work on mower blades but it's a lot more expensive than ER70S-6. You'll have to grind away some material beforehand as TIG welding requires good clean base material; meaning you'll have to grind way back up into the vee of the ding. Once ground and cleaned, you can then fill it. When lighting up on it, hit it hard quick with lots of heat, and start dabbing filler into it quickly, to keep the heat affected zone to a minimum. Once you start moving your filler puddle toward the cutting edge, you're gonna have to back way off the heat because the material gets thinner and thinner. But it also gets wider, so you might have to make more than one pass to get it filled up. Then at the end of your job, run your puddle around in a circle as you ramp the heat down. This helps prevent a crater and helps to avoid a crack at the end of your weld. Then you get to grind, and finally balance. I like to paint them after the work is all done, but I don't weld them very often-only on my own stuff for testing purposes, and even that's rare..

I would not use any other welding process for this job, MIG MIGHT work but you have little control over the heat. Stick is out of the question.

Next issue if you have to grind much off of the cutting edge, you are effectively making the cutting diameter of the spinning blade a little smaller; thus affecting cut quality. Reason being, if you look at the blade tips, where the cuttin edge meets the very outside edge, it's not a 90 degree corner-it's more like 95-100 degrees. As you make the blade narrower by sharpening, it makes the blade cut width smaller. I notice it on my yard after about 2 sharpenings I start to see a difference. So I just replace them every other season and I'm due for it this season. I'll put another edge on them about Sept, then mulch up the pine needles and leaves to finish them off.

Great info.

I have 2 sets of blades. When it's time to sharpen, I replace with spare then sharpen the ones I took off and get them ready for when they are needed again. I used the all american sharpner to get the correct angle for the blade and it only take a few passes to get done so it's not razor sharp / too thin.

Dan

 

[mikester]

My used blades go in my scrap bin and new ones go on after I cut the grass a few times in the spring.

New blades cut better and don't vibrate with imbalance.

New blades are cheaper than replacing spindles and bearings.

Having less lawn to cut is priceless.

 

[GreensvilleJay]

I've got 2-3 milk crates full of used blades, grab what I need, 'regrind' with a flapwheel in 4.5 angle grinder, make sure it's balanced. I don't worry about nicks or divots..heck they SELL blades like that now......

 

[dan_m]

I've got 2-3 milk crates full of used blades, grab what I need, 'regrind' with a flapwheel in 4.5 angle grinder, make sure it's balanced. I don't worry about nicks or divots..heck they SELL blades like that now......

I bought a balancer for a few bucks from amazon a long time ago. in my opinion better than trying the old nail trick.

Dan

 

[MOOTS]

Here is an example of a "gently used blade" that has a couple bigger nicks (not bad in comparison) after it's already been resharpended. This is about as average of a damanged blade as I've got.


in this picture, you can see a couple bigger (longer, not really deep) nicks.

View attachment 84708

here is a view looking straight down on the cutting edge showing the nick (middle toward bottom of picture) and you can see it's not as narrow (sharp) as the inside (top of picture) of the cutting edge. I'm not sure how "terrible of a cut" this blade will leave. If I can improve the cut, I'd rather do that.

View attachment 84709

In this picture you can see how deep the nick is on the cutting edge. The blade is laying against level/straight edge. I'm guessing maybe 1/8" max, probably smaller.

View attachment 84710


Dan

What type of grass and height of cut are you doing?

 

[D2Cat]

As Greensvillejay mentioned get a 4 1/2" angle grinder and a floppy disc for it, and a simple balancer and start practicing on what you have. Always clean off any dried grass on the blade before doing any sharpening. You can get an inexpensive angle grinder at Harbor Fgt for <$20.

When you have the edge cut the way you want it lay the blade on the balancer. If one end is lower than the other put a chalk mark on it and dress it down a bit more all the way across the cutting edge just to lighten it up so it becomes level.

The video you posted shows the guy grinds all the way to the center of the blade. He grinds too far from the outer edge and takes way too long grinding with that disc. Only grind where the original cutting edge is. Go quickly with short strokes and try to keep the blade as cool as possible.

I've seen these balancers for $5 at hardware stores or Wal Mart.

 

[dan_m]

What type of grass and height of cut are you doing?

I mow my lawn and a field.

My lawn is southern fescue blend - usually 2.5-3 height. At times, based on weather, it could be super dry or taller and thicker. Summer here in GA has been consistently in high 80s - 90s for several weeks now. We can get a daily thunderstorms but lately it's been missing me and not much rain last 7-10 days. a couple weeks bad, had 10-12 days of daily rain.

The field is bumpy and can be very tall where it needs mowed twice because it's so thick and/or tall. it has some rocks (golfball - baseball size) in some areas that occasionally get disloged and get hit with blades. I am not sure what all grasses/weeds are in field. This can be cut on highest setting depending on how long since last cutting. Also, it can have very tall ant hills and the discharge is nothing but a cloud of dirt/dust.

First time I mowed it, some of the shoots were as tall as I was sitting on my bx2380. since then, been able to keep it much lower, it gets mowed maybe every 2-3 months based on my schedule and weather. The first time I cut it, had to change filter it was clogged. Also had to clean out around radiator and screen.

Dan

 

[dan_m]

As Greensvillejay mentioned get a 4 1/2" angle grinder and a floppy disc for it, and a simple balancer and start practicing on what you have. Always clean off any dried grass on the blade before doing any sharpening. You can get an inexpensive angle grinder at Harbor Fgt for <$20.

When you have the edge cut the way you want it lay the blade on the balancer. If one end is lower than the other put a chalk mark on it and dress it down a bit more all the way across the cutting edge just to lighten it up so it becomes level.

The video you posted shows the guy grinds all the way to the center of the blade. He grinds too far from the outer edge and takes way too long grinding with that disc. Only grind where the original cutting edge is. Go quickly with short strokes and try to keep the blade as cool as possible.

I've seen these balancers for $5 at hardware stores or Wal Mart. View attachment 84719

I have a similar balancer that I used that I got from amazon a long while back. The blade I posted above was sharpened using the all american sharpner and my angle grinder. I'm not sharpening too much into the center of the blade, I'm following he factory cutting edge.

That's what I like about the all american sharpner, it gets the correct angle and sharpens in a straight line. I have the gen2 version of the one below in the video. I have a porter cable plug in and dewalt 20v battery. The sharpner comes with mount for many brands of grinders. Dewalt and porter cable are basically the same company.

My question isn't about how to or how much to sharpen a blade, but at what point a blade no longer usuable as a blade (should not be sharpened anymore). Specifically in the above pictures, is that blade sharpened enough to not damage grass to badly given the nicks - would you cut your own lawn with it?
Thoughts on reconditioning the blade in the above pictures? I got time and the tools to recondition - what is the best way? I'm not too happy with the first video I posted, it makes blade narrower and narrower and i'm not convinvced that's the best way and looking for other suggestions (weld and fill in gaps an option?)

They say time is money, I got time and tools to recondition and it using time doesn't empty the bank account. Given a blade is currently only $23 or so to replace, it seems a toss up. given how things are going with inflation and supply issues, could increase yearly. Also consider that i may need to replace 1 or more blades every season.

mainly looking at options to extend blade as long as possible with spending as little as possible out of pocket.

thanks for all the responses.

Dan