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Tom Rudd

Need advice cutting old saw blade

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I started to cut out a blade from an old heavy duty saw blade. Looks like it might take a while but I don't want to get out my torch And mess up the hardness of the metal. Is there a third option? A way to use the torch but keep the metal cool? Thanks in advance.

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I've cut saw blades with an angle grinder, cutoff wheels, and lots of patience. Old ones are usually work hardened and very tough.

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What kind of torch do you have? Because of the way an oxyfuel torch cuts (large kirf, preheat, etc) I doubt you would be able to cut anywhere near the lines without ruining the temper (which happens anywhere above about 400 F). Since it's so thin, you might be able to get away with using a plasma torch without too much heat bleading into the steel you wand to make into a knife. You would have to leave a bit of a margin around your lines, have a fast travel speed, and cool the metal in water quickly after you cut it. If you see colors appearing on the steel as it gets hot, you've likely ruined the temper in that spot and softened it. In my (very limited) experience cutting thin steel with a plasma torch, the "temper colors" spread about .25-.5" on either side of the cut, your mileage may vary.

 

I agree that an angle grinder is likely a good way to go, but keep in mind it still heats up the metal, so you should go slow and periodically cool down the cut.

 

One more option (and what I would likely go for) is cut out the blade the fastest way you can (torch or angle grinder) and just re-heat treat it. If you anneal the blank, you could save on abrasives pain and suffering while working it into a knife.

 

Good luck!

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On top of all that, that blade looks like it has brazed carbide teeth. The body steel may not be suitale for knife steel, being designed for toughness rather than hardness. The big mill blades without inserted or brazed teeth are usually okay.

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Thanks guys, the best option looks like my angle grinder. I'll keep you informed.

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Got to admit, I prefer using my plasma cutter for speed (and my lack of patience), and because I plan on heat treating all my blades before they're done, so demolishing the existing hardness isn't really a factor. Even with a grinder, I've had steel get plenty hot. I'd recommend cut a bit, cool it with water or oil, cut a bit more. But I'm a bona fide newbie, so take that for what it's worth, and a penny, and you might be able to buy a piece of penny candy.

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I use an angle grinder with a thin cutting disk. Just make sure to keep your angle shallow so it eases through and your disk straight so it doesn't bind up. Even though most are fiber disks with the abrasive impregnated into them, they can still shatter!

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Yup Brian, I dropped my grinder this weekend when it twisted out of my hands, landed on the blade and shattered it easily.

 

Alan, what kind of steel do you think it might be? it IS still after all the cutting (I was getting a few shades of color) very hard. I think the teeth might indeed be braised on.

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No telling. I know of one that turned out to be 4130, and one that was 1060. Could be anything tough. Note both of those steels are "hard" in the sense that they are tough to file. The only issue with them is edge-holding. Someone here once had a sig line quoting Roman Stoklas that applies here: "geometry says how sharp, steel [alloy] says how long."

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From what I've been able to find out, most are either 1045 or 1084 depending on the maker. Most can hit the Rockwell scale at or around 58-62. They have to be this tough to put up with the constant abuse they are put through. The problem is that you don't know which kind of steel it is. They'll make great knives, but you may find they won't hold an edge as long as a "known" steel. If u can, find some of the older blades without carbide inserts. These are invariably made of a tougher steel that holds their temper under constant abuse. Old sawmill blades are great for this, but dang hard to find anymore.

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From what I've been able to find out, most are either 1045 or 1084 depending on the maker. Most can hit the Rockwell scale at or around 58-62. They have to be this tough to put up with the constant abuse they are put through. The problem is that you don't know which kind of steel it is. They'll make great knives, but you may find they won't hold an edge as long as a "known" steel. If u can, find some of the older blades without carbide inserts. These are invariably made of a tougher steel that holds their temper under constant abuse. Old sawmill blades are great for this, but dang hard to find anymore.

now that you mention it, there was a even bigger sawmill blade at the metal yard when I was there last and it had no inserts. next time

I go I'm gonna get it. nice guy running the place too I talked him out of a huge old rusty file that is about 2' over all length...... 40 cents a pound.

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I use an angle grinder for cutting anything that might be heat-treated, and for more complex cuts. The cutting goes faster once you're cutting into an edge of the metal (same amount of cutting force on a smaller surface area).

It probably goes without saying, but definitely wear a respirator. It's amazing how fast abrasive dust accumulates in your airways.

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I use an angle grinder for cutting anything that might be heat-treated, and for more complex cuts. The cutting goes faster once you're cutting into an edge of the metal (same amount of cutting force on a smaller surface area).

It probably goes without saying, but definitely wear a respirator. It's amazing how fast abrasive dust accumulates in your airways.

I've gotten in the habit of wearing my respirator every time I grind pretty much anything. oh and I have a fan that blows from my left to my right. mostly past my left shoulder that helps cut down on inhaled metal dust.

Edited by Tom Rudd
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I see this too often and usually don't say anything. Let folks figure it out themselves.... but mystery steel is no good. Alan brings up a good point that it has inserted teeth. That is a telling sign that the body of the saw-blade is not worthy of a knife. Your best bet is to either pick up some actual beginner knife-maker steel (1084, NOT 1095) or pick up some O-1 round-stock from Fastnels to save on shipping costs.

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Your best bet is to either pick up some actual beginner knife-maker steel (1084, NOT 1095) or pick up some O-1 round-stock from Fastnels to save on shipping costs.

I started forging with O1 drill rods from Fastenal, it was good practice forging to start with round stock. I've stopped using them though because I've had problems with being pretty much unable to anneal blades forged from them (in thin pieces it almost seems like the stuff is air hardening).

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I started forging with O1 drill rods from Fastenal, it was good practice forging to start with round stock. I've stopped using them though because I've had problems with being pretty much unable to anneal blades forged from them (in thin pieces it almost seems like the stuff is air hardening).

I have always purchased my O-1 drill rods from MSC Direct. I find the quality and workability of the steel to be very consistent. 1" diameter, 36" lengths. O-1 can be tricky to fully anneal and requires about two days......... I typically just do 2-3 normalizing cycles after forging to soften it up and homogenize the grain. This is by heating to around 1600 and cooling in still air repeat 1 or 2 times but only heat to around 1450-1500. If you are cooling very slowly in your HT oven, or other insulated container, you will probably run into trouble.

Edited by Joshua States

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I found the reference from Kevin Cashen. Kevin says for working and HT'ing O-1:

 

Your normalizing temp of 1600F is good but your oven cool procedure is not, normalizing cooling should be done in still room temperature air. Slow cooling the steel via insulation or oven is annealing rather than normalizing and will result in heavy segregation of carbide constituents and even some grain growth. Normalize once at 1600F, and air cool. This will homogenize the internal structure particularly regarding carbide. Next, follow this up with thermal cycles to refine the grain size- heat more around 1475F or 1500F and air cool.

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Thanks for the info, Joshua. Despite being easy to turn into a serviceable knife (due to being very through hardening) it has some nuances, and I didn't know about those ones. When I forged from O1 I would let it cool down in the (coal forge). No wonder I dulled so many drill bits/had a very hard time peening tangs. I recently made a stock removal knife from some O1 stock and saw some lines going along the long axis of the bar as I was grinding, which I guess might have been carbides from the anneal at the mill.

Edited by Aiden CC

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Aiden, I definitely understand, but it's not really my point (fastenel isn't the best source). Maybe I'm just running out of patience but I do see a lot of folks suggesting and using mystery steel for beginners lately. I'm going off a tangent here but TV show's like forge in fire have been emphasizing "scrapyard" steels lately. Makes me cringe. It's not good practice.

 

I'm deeply sorry for going off subject a bit, not my normal routine, yet I feel it's important to know your steel.

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Aiden, I definitely understand, but it's not really my point (fastenel isn't the best source). Maybe I'm just running out of patience but I do see a lot of folks suggesting and using mystery steel for beginners lately. I'm going off a tangent here but TV show's like forge in fire have been emphasizing "scrapyard" steels lately. Makes me cringe. It's not good practice.

 

I'm deeply sorry for going off subject a bit, not my normal routine, yet I feel it's important to know your steel.

Yep. Unless of course you are just practicing grinding, shaping, handle making, and general entry level design (and don't have any money). Then using scrap for everything makes some sense. Just don't expect the finished product to be very serviceable other than general use around the shop or something equally unimportant. I made a railroad spike knife a few years back during a demo at an art show I was in. I made one alongside a 12 year old that I had do everything I did. We both ended up with a railroad spike knife and I gave mine to the guy who hosted us at the show. He still has that knife and uses it to eat lunch when he's in the shop. Repurposing materials has its place. Once a maker gets his techniques down a little then graduating to real steels and heat treatment is the way to go.

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Thanks for the info, Joshua. Despite being easy to turn into a serviceable knife (due to being very through hardening) it has some nuances, and I didn't know about those ones. When I forged from O1 I would let it cool down in the (coal forge). No wonder I dulled so many drill bits/had a very hard time peening tangs. I recently made a stock removal knife from some O1 stock and saw some lines going along the long axis of the bar as I was grinding, which I guess might have been carbides from the anneal at the mill.

Yep. O-1 is a great knife steel and I use it almost exclusively for my mono-steel blades (W-2 is a recent entrant into my blade stock). I don't know half of what Cashen knows, but I know enough about it to avoid the problems you have described. Try it again with the normalizing and thermal cycling Cashen outlines. I think you will find it truly addictive. It finishes really well.

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I'm deeply sorry for going off subject a bit, not my normal routine, yet I feel it's important to know your steel.

I think it's a good point to make. Using scrap steel can be an interesting challenge (like the KITH this summer or Forged in Fire), but in situations where you want consistent results, like when first learning to heat treat, making a knife to sell, etc, known steel is the way to go. That being said there are some cases, old (non case hardened) files being a good example, where scrap steel is almost a known steel.

 

Also, I'll go back and give O1 a shot next time I forge something from mono-steel.

Edited by Aiden CC

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A smith with any common sense can pick a good steel from a

scrap yard pile for anything he chooses to make, the lazy

and uninformed ones seem to always put it down for just those reasons.......laziness and/or lack of knowledge

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it seems the flood gates have opened. once people find out you want their old steel for practice knives suddenly you are up to your ears. the HR lady at work (a very nice lady too I might add) just gave me this morning a stack of lawn mower blades and an old axle. the axle intrigues me, seems like I've seen some pretty good knives forged out of steel axles. what say you?

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