Hardened cutting blade
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Matt_Jr
Platinum Member
I think it depends on if it's a high carbon steel or not and what the other ingredients in the steel are. This science is called metalurgy and I will admit I know just enough to confuse me more
. I know carbon steels and low alloy steels are quenched in water and high alloys are queched in oil or in an air oven slowly. Some are quenched in lead baths and salts too. Like I said, I know just enough to be confused. The stuff I harden are tools. I have over $100,000 in tools. Snap-on, Craftsman, Matco, Mac, Proto, you name it. I will probably never have enough. Anyhow sometimes I have to modify one to make it work 'cause what I need isn't available. Say I need to bend a wrench. I learned early on if I just put it in a vise and bend it it'll break. If I heat it up and bend it it'll be bent the way I want but break if I put some pressure on it before it does what I need it to do. If I drop it in a bucket of cold water while it's still hot it can handle what I need it to do and I can keep it to use again. I know they often use the color that the steel changes to as a guage on how hot it gets so that the tempering can be done at the correct temperatures. Both my grandfathers worked at steel mills in PA. One was a chemist. That doesn't make me an expert though. I just remembered a little. Wish they were still alive. I still had a lot to learn from them.
. I know carbon steels and low alloy steels are quenched in water and high alloys are queched in oil or in an air oven slowly. Some are quenched in lead baths and salts too. Like I said, I know just enough to be confused. The stuff I harden are tools. I have over $100,000 in tools. Snap-on, Craftsman, Matco, Mac, Proto, you name it. I will probably never have enough. Anyhow sometimes I have to modify one to make it work 'cause what I need isn't available. Say I need to bend a wrench. I learned early on if I just put it in a vise and bend it it'll break. If I heat it up and bend it it'll be bent the way I want but break if I put some pressure on it before it does what I need it to do. If I drop it in a bucket of cold water while it's still hot it can handle what I need it to do and I can keep it to use again. I know they often use the color that the steel changes to as a guage on how hot it gets so that the tempering can be done at the correct temperatures. Both my grandfathers worked at steel mills in PA. One was a chemist. That doesn't make me an expert though. I just remembered a little. Wish they were still alive. I still had a lot to learn from them.
Matt_Jr
Platinum Member
Oh yeah, tempering steel makes it harder. If it's too hard it becomes brittle. Another thing that makes them harder is whats in the steel. For instance, chromium, nickel, carbon, copper, manganese, blah, blah all in how much of each, one or the other and so forth makes the steel harder without becoming brittle. Tempering of steel is a very complex process that I don't know much of anything about. Just what I've done.....backyard crap. If I wanted a hardened cutting edge I'd be reaching for my wallet. Sorry for saying a lot of nothing.
.shinnlinger
Silver Member
I will share what my knowledge is...
ONly metal that has a high carbon content can be hardened by a simple quench. If you take a peice of rebar for instance and heat it and quench it, it wont do much (unless that rebar happened to have some carbon in it)
"back in the day" thay would wrap hot steel in horsehooves and bury it for a few hours to "case harden" it that is get the carbon from the hooves into the steel. THey still do this but I think it more sophisticated these days.
MOst tools are high carbon steel so MAtts observations are correct.
If you take a peice of very high carbon steel and heat it to red hot and then imediatly quench it in cold water it can become so hard that it will literally break if you drop it (sometimes it will crack just quenching it)
Since this is obvously not a desirable trait you can change it by "tempering" the steel. This is done by heating the metal again and "Drawing colors" If you have ever noticed how heated metal can turn blue, you have seen a color change. MOst tools like a "Deep straw" color as a happy medium. That is you heat the tool untill it is "deep straw" and then quench it. MOst tool companies have ovens that heat the steel to their desired temperature for a specific color and then quench. THe quench can be animal fat or salt water or used motor oil. pure water is the fastest quench, but sometimes it is desirable to have a slower quench to give the metal "toughness"
If you heated a peice of steel to red hot and let it cool off on it's own that softens its or "anneals" it and makes it flexible, somtimes too flexible as Matt has noted.
If you look closely at an axe head you will see it has a peice of hard steel at the edge to hold an edge, welded to a softer steel for toughness.
Back to the point of this thread, if you dont have a big forge I dont see how you would harden a cutting edge, and if the steel wasnt high carbon in the first place it wouldn't do much good.
old Grader blades are good bets, but with the cost of scrap steel rising, dont expect any freebies.
ONly metal that has a high carbon content can be hardened by a simple quench. If you take a peice of rebar for instance and heat it and quench it, it wont do much (unless that rebar happened to have some carbon in it)
"back in the day" thay would wrap hot steel in horsehooves and bury it for a few hours to "case harden" it that is get the carbon from the hooves into the steel. THey still do this but I think it more sophisticated these days.
MOst tools are high carbon steel so MAtts observations are correct.
If you take a peice of very high carbon steel and heat it to red hot and then imediatly quench it in cold water it can become so hard that it will literally break if you drop it (sometimes it will crack just quenching it)
Since this is obvously not a desirable trait you can change it by "tempering" the steel. This is done by heating the metal again and "Drawing colors" If you have ever noticed how heated metal can turn blue, you have seen a color change. MOst tools like a "Deep straw" color as a happy medium. That is you heat the tool untill it is "deep straw" and then quench it. MOst tool companies have ovens that heat the steel to their desired temperature for a specific color and then quench. THe quench can be animal fat or salt water or used motor oil. pure water is the fastest quench, but sometimes it is desirable to have a slower quench to give the metal "toughness"
If you heated a peice of steel to red hot and let it cool off on it's own that softens its or "anneals" it and makes it flexible, somtimes too flexible as Matt has noted.
If you look closely at an axe head you will see it has a peice of hard steel at the edge to hold an edge, welded to a softer steel for toughness.
Back to the point of this thread, if you dont have a big forge I dont see how you would harden a cutting edge, and if the steel wasnt high carbon in the first place it wouldn't do much good.
old Grader blades are good bets, but with the cost of scrap steel rising, dont expect any freebies.
shinnlinger
Silver Member
I hada "cheap redneck" way to do this thought....
OLd leaf springs(fairly high carbon) thrown in a good brush fire and heated to red hot and then quickly removed (you will need tongs) and clamped to a peice of angle or the edge of your bucket to flatten it. two sections of leave would proabably be long enough. Ideally you would heat it once and let it air cool to soften it and then drill your mounting holes and then do it again after it is flattend and holed but then throw it in a 55 gallon drum of water to cool imidiatlky after removing it the second time.
OLd leaf springs(fairly high carbon) thrown in a good brush fire and heated to red hot and then quickly removed (you will need tongs) and clamped to a peice of angle or the edge of your bucket to flatten it. two sections of leave would proabably be long enough. Ideally you would heat it once and let it air cool to soften it and then drill your mounting holes and then do it again after it is flattend and holed but then throw it in a 55 gallon drum of water to cool imidiatlky after removing it the second time.
have_blue
Veteran Member
shinnlinger said:
There ya go!
Big truck leaf springs are thick enough and far harder and tougher than stock cutting edges. If you can find a leaf wide and thick enough, and find a trough long enough to dunk it in, you've got a killer cutting edge.
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You can't just take HRS or CRS and harden it. They don't have enough carbon. Heating and quenching hardens the metal, tempering draws the hardness back a little bit so it won't break like a file. Hardening temp is usually bright cherry red (hard to get in a normal fire, but possible). Tempering temp is around 600F for 3 hours, if you can find a commercial pizza oven.
djw250
Silver Member
Another approach might be to weld on a hardend edge. Most welding rods and wire produce a much harder material than mild steel. You can weld an edge on, and when it wears, build it up again.
shinnlinger
Silver Member
Blu and 250 are onto something here.
I should point our that a leaf spring has enough carbon and hardness in it as it is. Yes a heat and quench will make it harder, but if you can clamp and bolt/weld it on "as is" it will still last a really long time.
Almost any excavator bucket has been "hardened" by welding...good point
I should point our that a leaf spring has enough carbon and hardness in it as it is. Yes a heat and quench will make it harder, but if you can clamp and bolt/weld it on "as is" it will still last a really long time.
Almost any excavator bucket has been "hardened" by welding...good point
You can use old sweep blades.
Farmers will have these. (around here dryland wheat farmers use them LOTS)
They are about 4'-6' on each side (they look like a big V )
I used one for the cutting edge on a home made box blade.
they are about 5"-6" wide, and 3/8" thick.
My uncle farms - he has lots of old ones.
Farmers will have these. (around here dryland wheat farmers use them LOTS)
They are about 4'-6' on each side (they look like a big V )
I used one for the cutting edge on a home made box blade.
they are about 5"-6" wide, and 3/8" thick.
My uncle farms - he has lots of old ones.
Pennsylvania Weldor
Member
- Joined
- Mar 16, 2008
- Messages
- 48
I buy my cutting edges from Valk Mfg, in New Kingston, PA. They manufacture all types of cutting edges, snow plow blades, grader/scraper blades. They can "harden" most anything in their furnaces.
The most common cutting edge is the "hardened" variety. Means the steel is tough enough to not break when hitting something solid, but the outside is heat treated to prolong wear life. The one's I like to sell my customers are the "through hardened" blades. They are still ductile, but of equal hardness throughout the entire thickness/width of the blade. Gives much longer wear life.
Heat treatment is a very involved science. For most of us that don't have the training or equipment, the oxy-acetylene torch is our method. Many of the posts in this thread are right on.
One method I use to "sharpen/harden" my cold chisels is: After grinding and reforming the cutting edge, I heat the end of chisel with a "carburizing" flame. Once the end becomes a dark cherry red I quench it in USED motor oil and allow it to sit in the oil until totally cool. Why used? Carbon deposits in the oil from the engine it was removed from. Because when heating something opens the "pores", the carbon will enter these open pores and make it tougher. Both the carburizing flame from your oxy-acetylene torch and the carbon in the oil will add toughness to the chisel. I use my chisels a lot, and only have to do this about once a year.
For any detailed info on heat treatment visit the American Welding Society web site. Lots of good info there.
Good posts everyone.
The most common cutting edge is the "hardened" variety. Means the steel is tough enough to not break when hitting something solid, but the outside is heat treated to prolong wear life. The one's I like to sell my customers are the "through hardened" blades. They are still ductile, but of equal hardness throughout the entire thickness/width of the blade. Gives much longer wear life.
Heat treatment is a very involved science. For most of us that don't have the training or equipment, the oxy-acetylene torch is our method. Many of the posts in this thread are right on.
One method I use to "sharpen/harden" my cold chisels is: After grinding and reforming the cutting edge, I heat the end of chisel with a "carburizing" flame. Once the end becomes a dark cherry red I quench it in USED motor oil and allow it to sit in the oil until totally cool. Why used? Carbon deposits in the oil from the engine it was removed from. Because when heating something opens the "pores", the carbon will enter these open pores and make it tougher. Both the carburizing flame from your oxy-acetylene torch and the carbon in the oil will add toughness to the chisel. I use my chisels a lot, and only have to do this about once a year.
For any detailed info on heat treatment visit the American Welding Society web site. Lots of good info there.
Good posts everyone.