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  1. #31
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    Jake (and anyone else), here's how to play with medium/high carbon steel.

    Don't forget, I am not an expert here...

    Take your file, and guesstimate it's age. If it's old (real old), then it's prolly water quench. If it's not so old, then likely oil quench. If yer not sure, then call it oil for now.

    Heat the stoopid thing up to red. Don't get too fussed, by the time it gets to red, the temper is shot and it's going to be soft. Unless you throw it in the swimming pool, it's not going to become hard again until you do something deliberate to it.

    Work on your chunk of now soft steel with whatever the heck you want to. Bash it with a rock, I don't give a cowpat.

    When it's the right shape you want, take a look at what you have inflicted on it. If you have just taken off some edges and made a bevel, then don't worry too much. If you have beaten it up, taken out large swathes, drilled holes and given it a real hard time, then it's (possibly/probably) going to go stoopid when you heat treat. If it looks complicated, stress relieve the thing. Similar to annealing it, but this time make and effort to let it cool down slowly.

    For you folks out there working wood, take a shopping bag of plane shavings (powered or hand) and set them somewhere fire safe, take your heat source and heat the thing up to very red, then shove it in the shavings and walk away. The shavings will burn, but they won't burn quickly. Should also scavenge lots of oxygen so the steel won't lose too much carbon if that worries you.

    What Andy did with the vermiculite is a good idea too, but don't worry too much about it if you don't have any. Perlite works well too.

    Anyway, when you have cold ashes and a hunk of steel, consider it stress relieved. Check it over again to make sure it hasn't bent or twisted. If it has gone out of shape a little, then bend it back. At this point, there should be little stress, and adding a little more stress by tweaking it shouldn't hurt it any. The more complex a piece is, the more chance it has of turing pear shaped when you really stress it up during heat treating. Keep the thing as simple as you can.

    Clean the thing up, with any luck it should be just covered in soot and a little scale, and should clean up ok. If you want a polished finish, get it smooth now because if you want to do it later it will be a cast iron female dog.

    Before you decide to heat treat, take a piece of mild steel, clean off any gunk till you have nice clean and shiny steel. 4" or more is better. Go to the kitchen stove and slowly heat one end. When the hot end is blue, throw some water over it to cool it down, and take it to where you plan to cook up your good steel. This multicoloured piece of snot is your own personal colour chart that will show you exactly what colours you will see, and isn't affected by some busted monitor or print out.

    Take your heat source, your bit of good (and CLEAN!) steel, a small magnet and a bucket of the desired quenching agent. Heat the steel up until the magnet wont stick, then give it another 5 seconds with the heat, then swish it around in the bucket full of water/oil/brine.

    If you had an undecided piece of steel, grab a decent file and try to file the good (hopefully hard) steel. If the file bites, sorry it was water quench, go back to heating till the magnet doesn't stick and swish it in a bucket of water and check it again. Files are typically about Rockwell 55-60C, and if the ex-file isn't harder than that then something is most certainly amiss.

    Now comes tempering. Best to do this ASAP after hardening, because your precious blade should now be glass hard, highly stressed and may crack, break or even shatter. We have to take some of that hardness out so it won't become razor sharp little slivers of pain when you drop the thing, and also so the edge might survive some abuse.

    Now that it's hard, grab your colour chart and a piece of #320-600 sandpaper. Rub a clean spot (cleaner and more polished, the easier to spot the colours), and apply heat to the blade gently, starting where you don't need it to be hard. For a plane blade, start way up the blunt end, heating from the side that doesn't have the edge.

    Once you get some colour starting, back right off on the heat. Stop if you feel like it, but go really slowly now. Gently flick the heat around the blade, warming it as slowly as is possible, till you see colours starting to get toward the pointy end. Once you see the colour you want, where you want it, put it in the water/oil to stop it getting hotter. With practise, you might not even need to dunk it, and swimming not really needed for the steel, it just stops the stuff getting too hot.

    If you do get the blade too warm, then go back to hardening. Don't worry too much, it's a skill that isn't too difficult to learn. If you can cook bacon and eggs without burning them, then you can temper steel. Remember that when tempering, slow is good and certainly doesn't hurt anything.

    Clean the blade up to what you want, sharpen the thing and enjoy.


    Things to remember.

    You have to do something really silly to foul this up permanently. If you cold work your chunk of steel (no bashing it while it's hot) then you can pretty much garantee that you will not permanently upset the steel. Losing carbon and burning happen when the steel is too hot, and it can't get hot by filing it, unless you file really REALLY fast.

    Getting the thing red hot is no garantee of anything. Making it hot enough that a magnet will not stick to the hot steel WILL garantee that you are doing something useful. Don't use a good magnet here, something small and cheap is good. Steal a fridge magnet if you have to. If the magnet will stick, then the steel is to cold for dunking.

    On that note, I have said red hot a few times. Generally, red hot is enough to get the job done. When hardening, you do need to be a little more scientific, and red hot might not be enough.

    Have a play with whatever you can find that's cheap. Springs are good, old files are great. Chances are that if you can play with it, it's not worth much and killing it isn't going to cost you more than a little time. Note where I said keep it simple? That's so when you foul the poor thing up, you don't get too upset. Whatever. Have a play, it's good fun and you can't really hurt anything, unless you get careless with hot things. Take whatever precautions you feel are needed with very hot things.

    The temperature stated on the gas torch doesn't mean very much. If it says 1,500c, then yes it does get that hot. Problem is that it will not get some large hunk of steel to that temperature. For little things like blades up to 1/4"-6mm thick and no more than 1/2"-12mm wide, a decent gas torch will get it hot enough to do good work. You might need to help it out though, which means something to keep the heat concentrated where you want it. A tin can with some charcoal is enough.

    To get something big very hot within a week, you need to be punching out lots of BTUs and putting them somewhere that they can't run away from easily. If you plan to tackle something large, then I would expect you have cut your teeth on some smaller stuff first. Learn to walk before running and all that.


    And there you go. Sorry for so many words, but there is nothing really scary about heat treating common tool steel as found in files. It's much easier to work when it's soft, much less chance of making a big mistake filing than grinding, and you can choose how hard you want the thing.

    Good luck, but you shouldn't need it.

    *Note: anything red hot is very hot. Take adequate precautions when playing with red hot things. Cover up bare skin in something that won't burn. Wear decent shoes and invest in some decent gloves. Avoid picking up anything with those gloves that might be hot, use pliers instead. If you don't know how hot is is, assume it's red hot and treat it accordingly until you KNOW it's cold.

    Wear something to cover at least your eyes too. For one, anything getting hot enough to make steel hot is giving off UV radiation, and we don't need any extra of that, two, there is a real chance of something popping when it's stressed and very hot. If it does that, well, I don't mind scars but I do like eyes.

    Oil used for quenching can catch fire, so make sure the area around your oil bucket is clear of anything flammable, and you have something nearby that will kill the fire. Sand works, water doesn't.

    Water will turn steam pretty quickly too, note where I said use pliers? Well the steam tends to cut through the gloves pretty quickly, and that's where the pliers come in handy.

    While it's not difficult to do these things, the nature of it can be dangerous. If it doesn't feel right, then DON'T!

    I hope that helps, and takes some of the fear out of playing with steel.


    Jake, I wouldn't bother welding that thing and trying to keep it hard all at once. If water gets to the weld, it's shot. If you can get that steel with lotsa carbon in it to weld nicely, then you should go buy a lottery ticket. It's going to be a PITA to weld AND have it stay straight. Make it soft, play with it then harden it back up. Also means you can really attack the thing and not worry about drawing out the temper.

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  3. #32
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    Thanks So much Schtoo,

    Thats the best description I've ever read. It seems to cover everything, whilst cutting out the BS. That post should be made easily accessable to others.

    Sounds like I should have more of a go ( well I better ! eh, bodgy )

    What I'm still a little uncertain about though, is why its considered to be a much much faster to take this harden/temper route. I know it means that you can 'blue' the blade to buggery in the annealed state and it doesn't matter.....uno while your shaping, so its quicker,

    BUT, I don't think I could shape them much faster anyway. Cause, for me, there's no avoiding pushing the blade into a spinning grinding wheel by hand. I can wear gloves I spose, but, it'll still get too hot to handle, and force you to stop or swish it in water to cool so you can keep going JUST LIKE I do right now when conscious of heat build up to avoid burning blade.......

    Not worrying about it bluing up will speed it up a little no doubt, but that saved time, I'm thinking, will be used up in the stress relieving, hardening, then tempering, then sharpening up again stages. Wouldn't it ? .... In fact, if I went much faster, I think I'd get ahead of myself and stuff up the profile I want to cut.

    Can I safely say, that if a blade never really gets much hotter than the temp where it starts to burn my fingers, then it doesn't really need to be stress relieved ? Cuase thats really the only rule I've used, and it seems to be sufficient.

    I do use white wheels, which grind far better I've found than the regular grey wheels that come with grinders. Those grey wheels blunten up quite regulary I've noticed. Need to dress them heaps, which means they are more likely to be used in the blunt (not much sparks) state, and consequently more likely to burn your blades.

    There's another thing that speeds up the process. I use thin cuttoff disks regularily via angle grinder to cut out big chunks quickly. If I just sat in the same spot cutting away, shore, it'll blue the steel, but it doesn't happen so quickly that you can't control it. These thin disks are just brilliant. Cause their so thin, the heat build up much less for the same amount of cut through when using a normal thicknessed disk.

    When I want to cut out a big chunk with these disks and I want to speed the whole process up, I slowly squeeze out water over the cutting area from a plastic pipet ......I must get a photo of this, this arvo. It really is a quick enough way to remove material fast, whilst ensuring I'm not burning the blade.....quick enough a way for me anyway. I'll attach a photo of a blade I cut recently. The big chunks cut out in the picture was cut out by this method. The whole thing was made from an old file, just from cutting out bits with thin disks, then shaping by pushing it into a grinder wheel . It doesn't look finished. But the important stuffs there. Flat backs, no heat damage at blade end etc. So it sits tight on plane bed, and the blades holding up very well.

    I suppose the only way to know, which is better is to first try the blacksmithing stuff.

    And it does sound like I should give the welding idea a miss. What I was thinking I could do amongst other things, was......make a cranked necked chisel, and also thinking about, being able to thicken up a file by welding a couple of regular ones together for an idea that requires a thicker blade. Its hard to get really thick files.

    As for the origional idea, detailed in this thread, their is no immediate need for that now. I found a better solution. It was to make a tool to rout out the bottom of a female sliding dovetail joint. With a little handle pushing down on top. I decided to use a 71 router instead. ...but, I gota say I'm still curious as to whether or not it would work.

  4. #33
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    Hey Schtoo,
    Great description, and as Jake says, without the BS! You might have convinced a few woodies to take the plunge!
    Quote Originally Posted by apricotripper
    thicken up a file by welding a couple of regular ones together for an idea that requires a thicker blade.
    I can see what you're after, but normal welding I don't reckon is the answer. If you can find someone to forge weld a couple together, it may work, being like a laminated blade. With a stick welder you'd only weld the edges, with unbonded layers behind, and the join itself wouldn't be hard steel. Start with a bigger chunk of tool steel or high carbon steel (car parts (axles, suspension members etc) !
    A crank-necked chisel isn't that difficult to make, just by hot bending the neck of a normal one...and heat treating afterwards!
    Still not convinced of the braze welding idea, but looking into it. The way I braze usually involved heating the workpiece up as well, not just the rod, otherwise the filler won't run and bond properly.

    Cheers,
    Andy Mac
    Change is inevitable, growth is optional.

  5. #34
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    Just quickly.

    If bluing the steel isn't a big concern, then shaping by grinder will not be a little faster, it will be a heck of a lot faster. What takes an hour now might take as little as 10 minutes.

    3 main reasons I can think of.

    1. No concerns about overheating, so you can grind longer, but still dunk it to cool it down, don't worry about it too much. Remember out little magnet? A grinder isn't going to get the steel that hot, so little is going to happen other than a sporadic annealing, which gives us...

    2. Softer steel cuts fatser. Once you draw the temper, the only way to get that hardness back is by heating it right up and quenching. If it's softer, the grinder bites harder and it takes less time, which leads on to...

    3. Giving the grinding wheels a hard time is good for them. They can and will glaze if you are too gentle, so really shoving the steel into the wheel will help keep them clear and cutting well.
    Be reasonable with the pressure on the wheels of course.

    Also, brazing any tool steel that isn't chock full of tungsten just isn't going to work. The act of brazing will kill whatever hardness you had, and the only way to get it back is to get it hot enough to undo the brazing. Steels with lotsa tungsten are typically high speed steel, and will go to very high temperatures without losing their temper...


    Edits and additions.

    I wish I could have said all that in much fewer words. Did you know there is a 10,000 character limit on posts? DAMHIKT.

    If you are worried about the tempering, are are having serious troubles 'catching' the steel at the right point, then run inside and fire up the oven. Set it to 220-230 degrees and let it warm up. To temper the steel, leave it in there for 10-15 minutes, longer if it's over 1/8" thick. Once it's done, pull the steel out and have a look. It should have a very light yellow hue, indicating you have taken some of the hardness out. If it's not visible, then your oven runs cold, if it's becoming straw/brown, then your oven runs hot. Aim for somewhere yellow to brown. Yellow being harder. Even better is some kind of very accurate thermometer you can stick in the oven.

    Adjust the temp accordingly if it doesn't work out well, and a good idea is a couple big hunks of steel above and below the blade to absorb heat. Good chance that some ovens will overheat the steel when they crank up. The bits of regular steel will help absorb the bigger fluctuations and protect the blade from overheating or not getting to sufficent temperature all the way through.

    Short version is that the proper tool is a kind of oven, and they run about the same temperature as what you would cook a pizza in for regular carbon steels. It's a perfectly legit option if you are having troubles with your tempering.

    For heat oxy is great, propane/LPG/MAPP are more than enough for smaller pieces. If you don't have some kind of serious heat available you have another option.

    Make a simple forge. You need something that will hold about 1kg of charcoal/briquettes, some way to let lots of air go through the burning fuel and something to provide the air. Hairdryers are just about perfect. A big tin can be the forge, make a hole big enough to let air in from the hairdryer and stick some charcoal in there. Light the charcoal, let it get hot then apply the hairdryer, slowly at first. I garantee that with minimal effort you will get something pretty chunky up to heat treat temps fairly easily with this setup.

    When you are done, cook lunch on it.

    Any questions, you know where we all are.

    And don't worry, people have been doing things like this for hundreds of years with lesser gear that you have in your kitchen.

  6. #35
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    Default Learning the hard way

    While I find various members efforts at DIY knifemaking commenable and I anm not for a moment criricising anyone ,I would like to make a point which I think has been overlooked.
    The metallurgical make up of the intended knife blade ( read cutting tool) can vary greatly.The is usually dictated by the access to the metal material stock the knifemaker has.
    The various materials have varying carbon and metallurgical make ups ( maganese,chrome ,vanadium content percentages all alter h/treatment temps,requiring slightly varying heat treatment and quenching.Some metals don't react well to slight overheating in seeking a quench tempearure.
    Some metals quench best in a certain oil mix and others in a water brine solution. Schoo is on the money with magnetic button tip.This whole exercise in heat treatment and quenching does not really reward half hearted attempts. The maker work out what he need to do accomplish then research how to go about it.Much of what has been written here is right but only half right
    There is a huge amount of material on amatuer knivemaking and amatuer blacksmithing out there on the net.Google is your friend .Fellas it is like cooking.You don't just bung and meal in the oven and let er rip. Different meals require different preparations and different cooking times.This is endeavour not too much different.

    With respect

    Grahame

  7. #36
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    I was waiting for this, someone had to do it...

    Grahame, I know as well as anyone that metallurgy has vast differences depending on what piece of metal you have. Some are easy to harden, others are not so easy.

    Really simple answer to all of it is:

    Who cares?


    I doubt that someone is going to find an old file made from anything other than plain (cheap!) high carbon steel. 90% of chisels that have been made till now are, again, high carbon steel. Springs, of the type that are candidate for being torch cut and bashed into a shape are 99% likely to be, again, high carbon steel.

    And 99.99% of all those items will happily and easily harden up with not much more than a gas torch and a bucket of oil or water. Tempering temps for all of them are well within the visible oxide range, so tempering them is easy enough to accomplish too.

    The intention of that post was not to scare off, but to encourage some folks out there to give it a shot. Granted, I know there are bound to be lots of failures, but that's nothing unexpected. I guess everyone failed at something the first time they tried.

    The good part is that most of the time you DO get something in return. Even if you miss the proper temps by a bit, you get some noticeable change. If what you got isn't good enough, then you either try again (practise makes perfect) or you try and find out why (knowledge is power).


    I really wish I could say what I really feel here.

    It's just that I am getting very sick and tired of someone telling me what I can and can't do, what will and wont work.

    At least I haven't stopped proving them wrong yet.

  8. #37
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    Grahame and Schtoo are both right in their own way, just slightly differing perspectives.

    For the use of scavenged High Carbon Steels Schtoo is on the mark, and I've never read anything as sensible, correct and user-friendly as his two "how-to" posts.

    Grahame brings up a good point, but I'd think that it is more to do with using alloys other than plain high carbon steel. I'd think that if I was going to buy some thing a little exotic, then I'd first download the product data sheet and figure out if I could treat the material as it should be. If I couldn't then I'd be pretty sure I would not get the results I'd be chasing.

    I watched a show on the ABC on the weekend with some old blokes from Central Australia (Epennara Station) that used a leaf spring fashioned into a rough adze for shaping a woomera. Just cut to shape and hardened in the bush. It was made because the wood they were using was too tough for a hatchet.
    I had the pleasure of watching them (as in the old men from that station) work steel when I was out at that station in '99. No Tempil sticks, salt bath, whatever, just a squeeze bag blower for the fire (made from roo skin and some pipe) and an old drum filled with water for the quench. They heated the spring and let cool to anneal prior to using a hacksaw to rough it to shape, then the file. Re-heat, quench, and sharpen. Bind it to a stick with roo gut, done.

    So, its either rocket science, or its not - depending on the material.
    Give those old lads something exotic, and they would probably suprise you, if they had the need and the time to fiddle around.
    Cheers,
    Clinton

    "Use your third eye" - Watson

    http://www.flickr.com/photos/clinton_findlay/

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