MattBower

I read about that too, and tried it once. Seems like it'd take some practice. :)

That's why jkmas suggested stacking a bunch of them together and clamping them. No bending that way.

Maybe something like that.

If it's a 1972 penny it's almost pure copper, so a hotplate wouldn't do it. The melting point is near 2000 degrees F. I think that'd be tricky to do with heat to pure copper without melting it. The design is still intact. With intense heat I'd expect some of the fine details to start melting. Might be possible if you were extremely careful, but I'm still leaning toward some kind of impact. (But if it was an impact, why isn't the edge damaged?) Interesting puzzle.

It depends what you're trying to braze. It'll work on thin stuff.

Possible. What year was it minted, Beejay?

Drop it from a great height onto a hard surface, and get lucky enough to have it land directly on edge? Or otherwise propel it edge-first into a hard surface at high velocity, edge-first?

Even the insulating refractories are not nearly as efficient insulators as ceramic fiber. Dense refractories are even worse. For example, at 2000 degrees F, Kaowool has half the thermal conducitivity of Kast-O-Lite 2600 (insulating), which in turn has about half the conducitivity of Mizzou castable (dense).

But if you've never had any trouble with it, how do you know they stand by their warranty? Sorry, I couldn't resist. It was a rhetorical question. You've had good experiences with the brand. I get it. :D

I guess you could also form a mild steel eye behind an A2 edge, and rivet the whole mess together. I'm just throwin' out ideas. At a certain point it may make more sense to just use a different steel. ;)

I figured anyone with chunks of hardened A2 lying around might also have access to a mill with carbide tooling, which is what sprang to mind when you hinted that you don't want to mess with the existing heat treatment. If'n you're going to have to slit and drift this stuff to make an eye, I doubt I'd bother with it. Forging air-hardening steel -- by hand, in any event -- doesn't sound like my idea of a good time. John Cohea makes a style of tomahawk that you could try. Personally, I have doubts that it'd hold up to hard use. But it'd at least allow you to keep the existing heat treat and avoid forging (although you'd still need to drill several holes in hardened A2). http://jmcknives.blademakers.com/Image_Knife.asp?Ident_Value=3280

Are you planning to mill the eye? I have not worked with A2, but I have the impression that it's reasonably tough stuff compared to simple carbon steels with similar carbon content (though not nearly as tough as some other tool steels). If it's free . . .

Yeah, I hate that part. (Not the filing -- there's something I really enjoy about the feeling of a sharp, high quality file peeling off steel. But sanding? Yech.) You notice that sword polishing is its own profession in Japan. Japanese bladesmiths aren't dummies. :)

Perlite makes good loose fill backup insulation.

Ric makes an excellent point, although I think he and I assumed different underlying reasons for your question. :)

I agree, Frank, that a traditional slow-cool anneal for steels above .8% carbon is counterproductive, for the reasons you mention. (It is worth mentioning that sources such as the Heat Treater's Guide generally do not recommend that sort of treatment for these steels.) I disagree that multiple normalizing cycles are smoke and mirrors, at least for simple steels. That's probably true for many tool steels, which tend to have alloying elements that do a very good job of "pinning" the grain boundaries and preventing grain growth. Even Aldo Bruno's vanadium-enhanced 1084 resists grain growth surprisingly well -- enough so that I know of some folks who've had trouble hardening it after the triple-normalizing routine. But for simple steels normalizing absolutely can make a difference; I have seen it with my own eyes, and you can, too: http://paleoplanet69529.yuku.com/topic/47099/Normalization-Grain-Size-Control-Experiment-----normalize I have also oil quenched steel without preheating the oil. Some steels are sufficiently deep-hardening that it doesn't matter. But some are sufficiently shallow hardening that it does matter.

I am familiar with HSS -- high speed steel -- but I had never heard of HHS until now. Here are a couple data sheets. http://www.alleghenytechnologies.com/defense/docs/081491%20ATI%20Def%20600-MIL%20Insert.pdf http://www.alleghenytechnologies.com/defense/docs/081057%20ATI%20Def%20500-MIL%20HR.pdf The ATI-600 ultra high hardness stuff looks interesting. It's like a lower carbon, higher nickel L6. Medium carbon, lots of chromium, a whole bunch of nickel, some moly and silicon. Should be really tough stuff. I'd guess it would air harden in thinner sections, just like L6 does. The ATI-500 high hard armor steel is similar, but with carbon in the .22%-.32% range. That's not a lot, so the max hardness is probably limited. I bet it'd make great struck tools, though.Or you could use it as a bright layer in pattern welding. Bottom line: I'd say keep some if they'll let you, regardless of which alloy you have. They'd both be worth playing with.

That's sort of what I thought. Simonds makes excellent files. I'm sure they're very good quality steel. But the file steels I have had analyzed were all pretty shallow hardening, meaning they need a relatively fast quench to achieve maximum hardness.

Semper Fi!

I have never made a spike knife. I buy known steel from Aldo and Admiral. But industry does have standards for some things, and for those who for whatever reason enjoy playing with scrap steel, it is possible to make some educated guesses as to what kind of steel certain scrap is made of, and thus how to heat treat it properly. I have no beef with those who want to try, as long as they have no illusions about it. I do think it's much easier to learn on known steel, though, and I recommend that.

It may be true that not all files are high carbon steel, but I'd be surprised if not all Simonds files are. Simonds is an excellent brand -- noticeably better than Nicholson, in my experience. (That's compared to new Nicholsons. I think the older Nicholsons were a cut above what they're now making -- not that what they're now making is bad.) I have never heard of Simmons files.

Make sure to preheat your oil to 120 or 130 degrees F. File steel is pretty shallow-hardening, generally, and shallow hardening steel wants a fast quench. Cold oil is slow. I'm actually wondering if you failed to successfully harden it the first time. That'd explain why you're finding it easy to push up burrs on the edge.

Grant, I see that this burner is up on Blacksmith Depot now. In fact I clicked through from there. There's one thing they don't explain, though: does it use MIG tips, or is there a fixed orifice? (And if it uses MIG tips, does it come with one already installed?)

It's a Gingery book. They're usually pretty good.

Extra insulation will certainly help with fuel efficiency. BUT, I think the theory behind how these things work is that the large interior volume helps reduce hot spots. Will one extra layer of Kaowool screw that up? Probably not. But I don't know for sure.