Crunch

lawnmower blade heat treating?

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OK, this discussion probably belongs in the heat treating sub-forum, and if so, I apologize, but it didn't look like there was a whole lot of traffic there.

Here's my question.

I have a 54" cut riding mower that uses 3 blades. Buying three blades from Sears will put you back $75 or more. To a person like me, who throws around quarters like manhole covers, this price is absurd.

I am a decent SMAW weldor and have the welder and rods and grinders and belt sanders etc etc, and I was thinking of cutting some small "strips" out of some old lawnmower blades and welding them in to replace the steel that has been worn, ground and eroded away, and then grinding on a new bevel and mowing grass.

Here are my concerns:

1. Are lawnmower blades (especially the edges) heat treated, and if so, will SMAW welding new metal in wipe out the temper? (I suspect not, judging from the obviously overheated grind jobs I've gotten from "pros" in the past, but if so...)

2. If so, how would one go about restoring the temper, if it's possible? Allow the weldment to fully cool, then heat the whole edge area until it's non-magnetic, then quench, then temper in an oven?

3. If so, what temperature(s) and techniques would I want to use? I'm sure I wouldn't want the entire blade to be too hard, lest it break and kill the neighborhood like a nail bomb...but I suspect the edge portion of the blade should be at least marginally hardened.

There are other issues that I'd want to discuss beyond this, but I'll throw this out there as a starter.

FWIW, I would be using 6010 or 6011 rod to do the weldment.

Thank you in advance for any replies. And please no "Just spend the stupid $75 and be done with it!" flames...I'm poor but have lots of rod and love to weld and am dying to learn about heat treating.

Best to all,

Jeff

Edited by Crunch

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well the big question would be what the blades are made of they make them out of alot of different metals depending were they come from i have honda mower and its got some tough blades on it and i bought some blades for another mower and they wore out in a year but i checked ebay and there selling sets of them for that mower for 30 bucks with free shipping

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Buy blades, it's a safety thing. The blades are designed to not fracture if you hit something. The pieces can come out like bullets and if it injures someone YOU are liable, and the mfg is harmless due to alteration of the equipment.

Lawnmower blades are edge treated with different processes, they are not homogeneous steel, and cutting a strip off of another blade does not mean you get a treatable edge.

If your "pro" overheats the edge, then the edge is softened and makes the blade wear faster. Learn to do a proper sharpening job yourself, it's easy and is best done with a bastard file and a vice. A hand held grinder is useful if you hit something and need to hog off some metal, but not best for dressing the edge.

Shop around, I am sure you can carve $20 off that price tag for some high quality blades that are made properly for your equipment but bear a different logo than Sears. I am using Oregon blades on my 46" John Deere, and they set me back about $50 for 3 blades. They were "rebranded" as John Deere, and I bought them from the local dealer. I think Sears sells a rebranded MTD machine, but could be wrong.

Many stores sell replacement blades so shop around before trying something so deadly. Us the old blades as practice mystery metal for something else.

Phil

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Go for it. I think that would be a good chance to learn something about heat treating. Even if it doesn't work all that well the worst that can happen (as long as it isn't a broken weld) is that you may have to sharpen them more frequently. What do you have to lose?

One thing you should watch for is the blade balance after refurbishing them. You will want to take care of the bearings. A year or two ago I rebuilt a three blade John Deere deck and the blades were the cheap part.

Good luck.

Bill

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I guess the real question is: Is saving $75 +/- worth the risk of serious injury or death if a home made repair fails? Remember, it's not just the person on the mower it could be anyone within 100' maybe farther. Any dogs, cats, horses, children, Spouses, neighbors or other valuables within that distance?

Mower blades are NOT simple steel anymore and the heat treatment is an exotic process not doable in the home shop. Any home shop I'm aware of anyway.

It's up to you of course but my non-flame recommendation is spend the $75 and sleep worry free. Or let the grass grow. Better yet, next spring buy a couple lambs and let them graze then next fall put them in the freezer. They'll keep your lawn cropped to a uniform 3/4" +/- fertilize as they go and taste darned good on the grill.

Frosty

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Hey, Crunch, please don't take this wrong, but these guys are correct, this is a very bad idea. Just the fact that you want to weld high alloy steel with 6010 or 6011 is more than enough info for me to know that you shouldn't be doing this. Nothing personal, but your neibors have a right to stay alive, even if you don't care about your legs and feet.

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If you are going to do this you need to use pre heat, post weld heating, the correct rods (not 6010 or 6011 they are just mild steel general purpose) and you probalbly need to peen the weld after welding to relive stresses and induce grain refinement. Then normalise it. Then you need to heat treat the whole thing back to standard OEM. But then this is when you dont even know what grade of steel they used in the first place. We use lawn mower blades to remanufacture blades for drain root cutters for the water board here but we buy new blades from a known supplier that supplies us a quality product of a known steel grade. We have programable tempering furnaces, hardness measuring machines etc, and have about 25 years experience in doing this and we are not welding them, only cutting drilling and regrinding them then heat treat.
Just easier to buy some new blades from the shop I think, or try Ebay. I suppose that we should be glad that you don't own a helicoptor and need new blades for that.

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Forgemaster: Who says you can't fix a watch with a big hammer? I'll fix that sucker!

Reminds me of (back in the day) when we would have blacksmith type guests at my old shop. Well, they had always heard stories of how the old hammer drivers could pick a piece pf paper from a wrist watch without cracking the crystal. So I would oblige them and borrow a wrist watch from on of my guys, lay it on the bottom die of my 1500 lb hammer, put the obligatory paper on it and grab the controls. I'd take a couple short strokes then send the ram to the top for a "whip-lash" blow and flat vaporize the watch! Hardly made a stain on the die. Blew them away! 'Course it was rigged and I kept a drawer full of $1.00 watches. What a hoot!

Edited by nakedanvil

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Bottom line is no one knows what the metal is, so a proper treatment of the blade is not possible. You are almost guaranteed to have the blade come apart when it hits something hard. Simply not worth the risk, no matter how much you save.

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Forgemaster: Who says you can't fix a watch with a big hammer? I'll fix that sucker!

Blew them away! 'Course it was rigged and I kept a drawer full of $1.00 watches. What a hoot!


I don't suppose you got pics of their expressions?

You'd make one heck of a fun neighbor you know that? :cool:

Frosty

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i do, and have done lawn mower blades and 5 h/p multi mulcher blades.....especially after welding i do NOT heat treat or quench after welding.......you dont want them hard in case you hit something and bits fly off.......i have yet to have a problem with a welded blade apart from balance..make sure nice good weld, no inclusions etc....really prepare the joint for welding if you are going to......the rest is flatter and shape.....still no quench...regardless of what steel.:)

hope this helps

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Thanks for the replies, everyone.

Hey, Crunch, please don't take this wrong, but these guys are correct, this is a very bad idea. Just the fact that you want to weld high alloy steel with 6010 or 6011 is more than enough info for me to know that you shouldn't be doing this. Nothing personal, but your neibors have a right to stay alive, even if you don't care about your legs and feet.


Thanks, aftist, didn't know lawnmower blades were "high alloy steel." Doesn't 601X penetrate well enough to weld it? Or is 60kpsi tensile strength not enough (but 70 or 80kpsi is)? Oh, and I don't have neighbors and it's a riding mower (feet above deck) so not to worry. :D

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Hey Crunch, 6010 and 6011 are general purpose, mild steel rods. Sure they penetrate deep, especialy 6010, and it probably will not be the weld itself that fails...yet failure is almost sure to ensue. At a minimum 7018 is needed for anything medium carbon, along with proper procedure.

As was mentioned, The best solution to your problem, IMHO, is to learn to sharpewn the blades yourself. You will likely find that they last five times longer or more if you do them your self. I sharpen blades for a local lanscaper. I don't care how much metal I take off, as long as he likes how sharp they are. Thats not really true, I don't wantonly waste the metal, but I am certainly not all that carefull either. Buy some new blades, sharpen then with a file.

Edited by arftist

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I don't suppose you got pics of their expressions?

You'd make one heck of a fun neighbor you know that? :cool:

Frosty


HA, I was thinking the same thing

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i dont weld to prolong, or add, only to repair broken sets, and if forged/flatter'd to re edge/shape, i still dont heat treat lawn mower blades.


i still dont heat treat lawn mower blades........!!!!!insert.........HARDEN or temper......IMPLIED....:)

Edited by double_edge2
explanation for a tilted to the right type person clarrification

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My buddy bought this thing for balancing a lawnmower blade. It is really simple. Excuse my picture, I know it is crude. The red part is the lawn mower blade. The blue part is a washer like thing with a pin that goes through the bolt hole in the blade. The black lower piece is a a metal cone. The blue piece has a small dimple drilled into the bottom. The pointy tip of the cone sits in the dimple under the blue washer thingie. Then you just set the blade on the washer and the washer on the cone. The blade will not only show balance from end to end but also from side to side. It's amazingly simple but perfect for determining proper balance of any blade really. As long as it has a center hole, you can check balance with this thing. I'm sure it would be so easy to make.

balance.jpg

Mutt

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OBTW for what it's worth: Engineer friend was working on a product liability case. Seems a local municipality was interested in this new road side brush cutter, the dealer mounted it on one of his excavators and set up a demo. All the mucky-mucks in their suits come out to watch. Well, it seems the hydraulics were not compatible flow-wise and this thing spun up to some hellacious RPM and totally scattered. Two on-lookers were killed and four others seriously injured. Like I said, "for what it's worth".

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double_edge2: Heat treating is not always a deliberate thing. To me, ANY TIME you apply heat to steel, you are heat treating it. Welding, forging, cutting, they all affect the heat treated state of the part. So, I don't agree that you "never heat treat lawnmower blades".

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double_edge2: Heat treating is not always a deliberate thing. To me, ANY TIME you apply heat to steel, you are heat treating it. Welding, forging, cutting, they all affect the heat treated state of the part. So, I don't agree that you "never heat treat lawnmower blades".


my mistake i accept your apology......i allow it to cool, not in a forced breeze to accelerate cooling, nor place in a liquid at any temp to reduce heat or aid in warping or hardening a weld, nor do i RETARD, its cooling in any way by deliberately smothering in any solution, gas or chemical substance either powdered or liquified.

"""So, I don't agree that you "never heat treat lawnmower blades""""......

the ones i purely press....i did not heat....noticably by eye, touch, etc.

"""ANY TIME you apply heat to steel"""

although i suppose i should heat treat them with a cigarette lighter first as that would be a heat treatment and less shock to the grain structure.

:D

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I have been thinking of some Stellite treatment on my blades. $75 seems high, I get really good blades from John Deere for much less than that. BTW, my favorite mower is a 111 JD rider that I put an 18 horse twin into.

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I have been using some old mower blades as raw material for garden tools... I like the steel as it mostly seems pretty strong. I have even made one into a plane blade (took some patience to get that upset to my desired thickness). It seems like you tightwads are threatening my steel supplies with your excessively thrifty ways! JUST STOP NOW! I will heat treat them after I retrieve them from the scrap pile, thank you!

Grant I want to try that with my new Anyang! I will get some watches from the dollar store. I have some people that want to come over and see my shop... this will be great! I have to look properly chagrinned when the hammer falls! I must look shocked and embarrassed! WOW! It's gonna be FUN! Thanks for sharing this kind of real blacksmith lore! This is what's so great about this forum! It's the best place on the web since the old "Badger Pond"!

Clay

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