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  1. #1
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    Oven-less tempering?

    Question time again (thanks for your patience! )

    From what I've seen about tempering, the item is first heat treated then popped in the oven to temper.

    What if I don't have an oven or the piece is too long to fit?

    How easy is it to temper the piece in a forge, and what other options are there?

    Many thanks, bolo

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    Re: Oven-less tempering?

    colours. Once hardened, clean the blade to bare metal (not polished, just so you have bare steel showing across teh full length and width of blade), then find a heat source (blowtorch, forge, hob on your cooker, etc). You need to carefully heat the blade to the correct temperature for the temper you are after.

    Don't believe the books that say 'straw colour is RCxx', it is steel specific. When colour tempering I take a piece of the steel I will be using, harden it and then cook it in the oven at what is supposed to be the right temperature according to the manufacturers. I look at the colour achieved and test the hardness with a file (i've got hardness files, but you get a feel for these things). Then I have something to compare the blade to when I come to temper it, like a colour chart

    In an ideal world you want a softer/springy back and a harder cutting edge, so blue/purple at spine and straw/gold/brown at the edge. Start heating from the back of the blade and play the heat along it until the colours start to appear. As they reach teh correct colour at the edge cool it off a bit with a dribble of water until the rest catches up. Watch out coz the edge and the tip will heat up fast compared to the thicker spine.

    It takes practice but is a time honoured way of doing it short, wide blades are easiest because you have time to see the coours moving, long and thin baldes are therefore the more difficult. Also, make sure you don't touch the bare blade before tempering as any oils will give a false colour!
    Don't just tickle it...


    dave budd handmade tools knives, tools and courses makin' them! 2013 Course List NOW ONLINE!

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    Re: Oven-less tempering?

    Think I'll leave it to you Dave sound complicated for us mere mortals

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    Re: Oven-less tempering?

    Many thanks, Dave.

    I don't think I've ever learned so much in such a short space of time.

    Best regards, bolo.

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    Re: Oven-less tempering?

    nah, it's a doodle

    really, just watch the colours moving and keep on top of it. When I teach people knifemaking with my ancient forge setup that is the way we have to temper our blades. So far nobody has cocked it up to the point of needing to reharden and start again (though some are not quite spot on, they are good enough to make a useful blade). Start with smaller pieces and work up
    Don't just tickle it...


    dave budd handmade tools knives, tools and courses makin' them! 2013 Course List NOW ONLINE!

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    Re: Oven-less tempering?

    I will do, mate. Cheers.
    And the wife will be more than happy if don't have to use her kitchen appliances for it!

  7. #7
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    Re: Oven-less tempering?

    One thing when tempering this way is to take it slowly, its pretty easy to go too hot and ruin it. Dave is a pretty damn good teacher thats why he hasnt had anyone overheat a blade, ive done it two or three times.

    If your into forging its realy worth buying Tim Livelys dvd, he does everything without electricity so he always tempers over a forge, it really helps watching someone do it. Also his forge design is brilliantly cheap.

    Jamie

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    Re: Oven-less tempering?

    It is worth remembering that oxidisation coulour are NOT a direct indication of any given heat .they vary from steel to steel and show different depending on the atmosphere you are heating in ,the presence of oil etc .
    You are also giving a snap temper ,ie heating for very little time .
    you can make a good knife this way but in order to get consistent results one needs temperature control of some kind .
    edit to say I am repeating Dave .............
    please email me if you want to contact me ,my PM box just gets so full .
    owen@owenbush.co.uk

    www.owenbush.co.uk

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    Re: Oven-less tempering?

    that's a good point Owen makes, it is only a single temper. I always make sure to check the colours on both sides of the blade to make sure the heat is working through the thickness (also helped by the fact that we are applying the heat from the spine and not the sides of the blade). Also it is best to repeat the process several times to make sure you have attained the correct temperature, On courses I tend to encourage students to only do it the once on account of the fact that you then have only a single chance to screw up rather than three

    An oven is better, but colours do work. slow heating is better than fast, so a soft torch not an oxy-acet, that way the steel has more of a chance to temper evenly throughout it's thickness. I use the hot charcoal from the forge and take it slowly. Make sure you have good light and not trying to do things in bright sun or deep shade, colours are a matter of persception (hence the test piece from the oven, but as Owen also points out, contamination will change the colours too )

    Go for simple steels that have a wide range of useful tempering temperatures. So if you have a blade fall within a 4 or 6 RC points range, then you still have a good blade. Some higher alloy steels go from rock hard to soft in a matter of 20C and are not the best choice for this method.

    play with it and test things as you learn
    Don't just tickle it...


    dave budd handmade tools knives, tools and courses makin' them! 2013 Course List NOW ONLINE!

  10. #10
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    Re: Oven-less tempering?

    Thanks Guys,

    I have always wondered if it was possible to do this, I think it should be in a new section on BB

    Questions you always wanted to know but were afraid to ask

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    Re: Oven-less tempering?

    I coloured tempered a blade today, a small penknife blade. Tempered twice and its good to go. I also tempered the tang to blue to better match the hardness of the spring and reduce wear, the rest of the blade was straw. Colour tempering is extremely useful because it allows you to make blades with differential hardness which you can't do with an oven without a lot of faffing about.

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    Re: Oven-less tempering?

    I use a large piece of mild steel. Chuck it on the forge and heat it then put the item on it and move the piece around to get the colours running. You need to temper two or three times as in the Lively dvd which I cannot recommend enough.

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    Re: Oven-less tempering?

    Quote Originally Posted by rmcpb View Post
    I use a large piece of mild steel. Chuck it on the forge and heat it then put the item on it and move the piece around to get the colours running. You need to temper two or three times as in the Lively dvd which I cannot recommend enough.
    I totaly forgot about using ahot steel bar to temper. If you do have a forge this is by far the easiest way to temper without an oven, because you can get the bar to an even temp, rather than with coals where you have no way of telling if one parts hotter than another.

    Jamie

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    Re: Oven-less tempering?

    Excellent advice all round! Thanks guys.

    What about the tang?

    All the footage I've seen (which is limited, admittedly) has the tang sticking out of the forge.

    If I'm making longer pieces, is the tang heat treated along with the blade, and do I temper it to the same colour as the spine?

    Also, after tempering, is the piece just left to cool?

    Thanks again, bolo.

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    Re: Oven-less tempering?

    once the blade is how you like it just stick the end of the tang in the coals/torch and draw it to purple/blue/grey-green, basically soft or springy and cool it once it gets to your cutting edge
    Don't just tickle it...


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