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Alan Longmire

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Posts posted by Alan Longmire

  1. Indeed.  Back around 1990 or so, a bunch of smiths led by Don Fogg and Jimmy Fikes, in cooperation with Jim Batson, started questioning the conventional wisdom of things.  Jim had pioneered using the hydraulic press for forging damascus in the early 1980s. Always trying to improve things, he and Jimmy (this story in long form is in two issues of Knife magazine from last fall) were trying to weld larger billets without a.) letting them soak in the fluxed-out crap that lines the bottom of a forge and b.) maintaining an even heat.  The vertical forge with blown burner was the result.  Don adopted it, and showed it to everyone in the Knifemakers' Guild. By the end of the 1990s all the big names were using them.  The advantages are great. No leaving the steel soaking in the soup of nastiness, very low scale from the neutral to reducing atmosphere, and a very even heat the full width of the forge.  The disadvantages are that you need a welded-on handle for the billet, or at least one much longer bar you can hold with tongs while it heats up, and the fact that you can't put it down in the forge to soak in heat. Oh, and if you do drop something in it, you have to take the lid off or pick up the body to retrieve it.  Not easy or fun while it's hot.

     

    If you're not making damascus, they have no downsides other than the dropping stuff thing.  Think it's not a long enough heat? Make it wider.  I've seen them up to 24" across inside.  And Randal Graham used to heat treat full-sized katana blades by stroking them back and forth through his 8" diameter vertical.  Takes a while, but if you're good you can get an even heat on a long blade in a small forge. They work great with blown or atmospheric burners, but blown are easier to tune.  Well, you have a T-rex, and they're pretty easy as well.  

     

    Edit: Geoff posted those sweet ribbon burners while I was typing.  Yowza!  You'll need the injectors, though.  A MIG tip would work, but I have no idea what the orifice size would be or how far into the venturi to put it...  If you made a little side box for those with just the slots exposed to the forge interior they shouldn't melt.  

  2. Scotchbrite belts will round over the ridges.  If you're really after a satin finish, hand-sanding with 400 will do it.  Single sheet on a hard backer will keep the ridges crisp.

  3. 50 minutes ago, Matt Robert said:

    so the small amount of material loss won’t really alter the POB or flex of blade then by much if anything correct?

     

    Correct.  We're talking maybe half a gram of material at most, and that will be evenly spread across the entire blade. Any difference should be imperceptible.

  4. If you're comfortable working in a vertical forge like the ones Don used to make, you can't get much simpler or more portable than a modified version of Jeff Pringle's Nuclear Marshmallow.

     

    1. Roll up two layers of kaowool to make a tube about 8" internal diameter and 24" tall. Secure with wire binding.

    2. make a lid and a base out of a single thickness of wool. You may have to stiffen the lid with wire.

    3. poke burner into bottom side about an inch above the floor. tangent or not, doesn't matter.

    4. cut doors just below lid.

    5. light, wait three minutes, begin forging.

     

    It won't be terribly durable, as the wool will be brittle after firing, but if you're careful it can last a good while.  Plus it'll cool off almost instantly, except for the burner.  

     

    To forestall anticipated questions from others, no, fired uncoated kaowool is not a lung cancer hazard. Just a dust hazard.  Industry uses it uncoated, and OSHA only requires a respirator during replacement. For dust, not airborne fibers.  It is not asbestos, you can't get silicosis from it, it's no more dangerous than fiberglass insulation. The only reason we put it in a hard shell and line it is for durability. It's too easy to poke holes in an unlined forge, and if you use flux, hot flux eats kaowool like boiling water easts cotton candy.  

     

  5. Unless you grind on it for a very long time at 400, no, you won't lose a lot of material.  You do risk ruining the temper, so keep it wet if possible.  

     

    I assume you want the 400 grit for a finish, and this is on a heat treated blade finished by someone else?

  6. I suspect they're too finicky for average home shop use, or they'd be in everyone's shop.  I know machine shops have to be really anal about water-soluble cutting fluids and lubricants, checking viscosity and specific gravity on a daily basis to make sure they're still doing the job.  Since the stuff has been around for 30 years or so, seems like if the polymer quench was easy and repeatable without much maintenance all the knife supply places would sell it.  The fact that they don't makes me think it's not suited for small-scale or occasional use.

  7. And done.  You're fully back, with all previous posts accounted for! Your post count jumped from 9 to 955, as it should be. B)  And you've got access to all your old PMs.  The only thing I can't seem to change is the join date.  We'll leave that as an exercise for internet detectives to figure out how, if you joined the forum last Friday, you have posts dating back to 2007. :lol:

    • Like 1
  8. Short answer: carbon content and carbide formers.

     

    All wootz is crucible steel, not all crucible steel is wootz.  

     

    Long answer: Wootz/bulad/fulat is/was made from a very high carbon source like cast iron, melted together with certain organic materials. It tends to be 1.5%+ carbon, up to 2%, verging on cast iron, but by virtue of the carbide formers (often cited as vanadium and/or chromium from either the organic materials or the ores) and lengthy time in the furnace, the carbides are deliberately segregated to form a pattern of extremely hard martensite with embedded carbides in a matrix of soft perlite/cementite that holds it all together.

     

    Western crucible steel/cast steel as produced from ca. 1760-1900 was made from carburized wrought iron in the form of blister and shear steel, melted in a crucible to remove all slag. Carbon content is rarely over 1.2% (usually much lower), and there are no deliberately added non-iron carbide formers.  Any patterning is purely incidental.

     

    Don Fogg asked this very question back in the day, and got a much better set of answers here: 

     

     

     

    • Like 2
  9. Jerrod beat me to it, I didn't have time yesterday afternoon.

     

    But yes, the sand is simply for thermal mass.  When I temper in a toaster oven I have a slab of 1" brick to add that mass.  What thermal mass does is even out the fluctuations inherent in electric ovens.  It's a good method for most steels.  Which brings me to...

     

    Unknown steels.  They are just that, and the only way to determine the best way of hardening and tempering is to experiment.  Automotive leaf springs are usually, but not always, 5160 or 9260. The HT for these is pretty similar, heat to 1525 F (that's well past nonmagnetic, don't use a magnet for precise heat treatment), quench in warm light oil like canola, do NOT use motor oil, temper at 325 - 400 F for knives. Lower tempering temperatures equal harder but less tough blades.

     

    Older (say 1950s-2000s) Automotive coil springs are usually 5160 or 9260, but after around 2005 they may be HSLA (high strength low alloy) and not hardenable by simple methods.

     

    There are no rules for junkyard steel. The parts are made to meet a specification, and the manufacturer will use whatever steel is cheapest that meets that specification.  

     

    As for leaving the steel in the sand (or oven) to cool after tempering, that's not necessary at all.  

     

    For the history behind all this, that's a very thick volume indeed!  Search around this site, there's a LOT of information.  To get you started with the basics of good home heat treating, search the term "decalescence."  

  10. 6 hours ago, Alveprins said:

    Solvang Custom Knife Show

     

    Ooh, an actual Norwegian at Solvang?  That'll be nice!  :)  Seriously though, that's one of the great shows.  I predict good things!

    • Like 1
  11. Late to the party here, but Superquench is pretty well understood.  Adding the detergents and wetting agents eliminates the vapor phase and greatly reduces the nucleate boiling phase of the quench, thus speeding cooling to the point that steels with as little as 0.2 - 0.3 % C and over 0.5% Mn will fully harden.  This is also why it will destroy anything with more carbon and Mn than A36 mild.  It doesn't turn mild steel into tool steel, it just makes it very hard via overstressing it.  It's a fun science trick with little practical value, unless you need a single-use chisel and you have superquench but no tool steel.

     

    To August specifically: [warning! vast oversimplification ahead!] faster is not necessarily better. You need to match the quench to the needs of the alloy you have.  And I second Jerrod that ice cream is one of the best uses for liquid nitrogen unless you're using certain high-alloy stainless steels.  And we don't know exactly what, if anything, it does to those besides allow more retained austenite to convert to martensite prior to tempering. That alone is what adds a point or two of hardness and a few ft/lbs of toughness.  Retained austenite is soft, lowering the overall average hardness. It also has an annoying tendency to convert into untempered martensite when stressed, which in turn lowers toughness.  Finally, if left too long or fully tempered first, it becomes metastable and can't be converted by further cooling.  So, if you're going to do cryo, do it immediately after the initial quench. Do not snap temper, do not leave overnight, do not pass go. As soon as it's cool enough to handle, straight into the cryo.  I've never heard that bit about slowly warming it back to room temperature, maybe that's something with carbide tooling.  Or just magical thinking, we get that a lot in metallurgy. :lol:  For all the blade steels I know that show a benefit, it's quench, immediate cryo for an hour or three, let warm to room temp in still air, then immediately into the tempering oven. [/oversimplification]

    • Like 1
  12. Very nice!  It may be technically cheating to the purists, but the results are pretty darned spectacular.  Personally I don't think it's cheating since you do take it fully molten and follow all the other steps of the process, unlike a certain guy who shall remain nameless, who used to thermal cycle the heck out of S7 and call it wootz.  

     

    I figure since you have the right ingredients in the right proportions, and you're changing the carbide structures via liquidus, it's wootz, period.  B)

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