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The Newbies Arena Are you new to knife making? Here is all the help you will need. |
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#1
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Temper question
I waited a few days until I tempered a blade, was that OK?
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#2
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Traditionally I think most would suggest to temper them within a day, some people cryo there blades so that takes time and such. I think I've heard the arguments and such about tempering them asap, but I can't recall the exact reasoning. I'm trying to figure out why it would make a huge difference (all outside effects that would come into play, rusting ect. not into the equation), I don't know what would make the crystalline structure (or why) change once it's been cooled to room temperature, which you do before tempering.
But I'm sure someone will stumble by that knows the scientific reasoning, or why it doesn't matter. I have a metallurgy book that I used for a class I took years ago about 15 ft. away, but honestly I'm just too lazy at this point in time. |
#3
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It's best to temper immediately after the quench as a rule of thumb but, in fact, it can vary with the steel in question. Tempering is done partly to soften the steel so that the blade is durable but also to relieve stresses in the steel caused by the quench. Many steels can quite literally tear themselves apart in a few hours if left untempered. Usually, this is very visible and obvious but it is possible that small cracks form that might not be visible until the blade fails at some later date after being made into a finished knife . I watched one of my untempered blades split lengthwise into 3 thinner blades (more or less) on one occasion. Again, it depends on the steel. Oil quenched steels are very likely to crack if left too long but air quenched steels probably wouldn't. Thin blades are probably less likely than thick ones. O1 can be used at full hardness (not as a knife though) but S3V can't and so on ....
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#4
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That's what it was, I knew it was something obvious I just couldn't remember. Sometimes the most important things are forgotten and quenching a chunk of steel that is close to 2000, is probably the most stress that a blade will ever see.
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#5
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As Ray replied all kinds of things to consider that might effect the quenched blade, geometry, composition, carbon content, etc. If you don't know for sure why chance it? Plan ahead and have your tempering oven up to heat and ready. Out fit it with a timer/cutoff so you don't have to babysit. If you don't have time for the number of tempering cycles you think you need or prefer, at least get the initial first cycle done. Then you won't find out the hard way that you shouldn't have waited. Pretty much a no brainer in my book.
Some steels will fool you. You wouldn't think some of them would be all that picky but other factors (above) come into play. Thicker blades with substantial curves, for example. The thicker section may feel reasonably cool to the touch but is still stabilizing and "moving" internally while the edge is set. This can cause micro cracking along the edge due to changing stress factors and with steels you wouldn't expect. Did a himalayn farm knife out of 5160, stalled on the tempering cycle for a day (everyone "knows" 5160 isn't prone to cracking), didn't really check it closely and finished out the blade later ....... two 1/16" micro cracks right along the working curve showed up in the final etching. "Aw crap" moment for sure. Bottom line, you lose nothing by planning ahead and just doing it. __________________ Carl Rechsteiner, Bladesmith Georgia Custom Knifemakers Guild, Charter Member Knifemakers Guild, voting member Registered Master Artist - GA Council for the Arts C Rex Custom Knives Blade Show Table 6-H |
#6
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Well the only thing that may help me is, this was the blade I had to re- HT after the the decarb to hot deal, I'll just continue to final grind and see what it looks like. Thanks lesson learned.
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#7
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One thing that you could do if you are short on time to do a full tempering of the blade is to stick it in the oven for an hour at about 350? to relieve the stress then do a full tempering when you have the time.
Doug __________________ If you're not making mistakes then you're not trying hard enough |
#8
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This is what I always do while my one and only electric furnace cools down enough to temper. I soak it in the kitchen oven at 350 for 2 hours. I usually cryo treat it overnight next, then temper the next day.
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#9
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I am trying to understand this too. I read that the steel should stay slightly warm between HT and tempering. I also read to wash the knife off then I read not to but to wipe it off as best you can. If the knife is cooled all the way down is this where the risk of cracks become an issue? So is washing it bad?
Sorry JawJacker, this seems to go together so I didn't want to start a new thread. |
#10
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The way I read it is, as soon as you can hold it, wipe all you can get off with a rag while its warm, throw it in the oven to temper.
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#11
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What Jaw said. I wouldn't wash it. Most of the literature says the blade should cool to about 100 degrees or a little higher. That's just cool enough to be able to handle it without it feeling uncomfortably hot...
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#12
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I usually scrub the oil off with a wire brush, detergent and hot water. Don't be too quick to get the blade into the tempering oven or you will risk it not cooling low enough to finish converting to martensite. Wait until it's cool enough to handle with your bare hands.
Doug __________________ If you're not making mistakes then you're not trying hard enough Last edited by Doug Lester; 06-03-2013 at 10:58 PM. |
#13
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Easy rule of thumb.....about the same heat as hot water from your tap (around 110 to 120). Ergo, clean with hot soapy water if you plan to stick in the wife's oven (and like sleeping inside). One of those soap holding pot scrubbers works really well and fast. They have a scotchbrite scrubber built in.
__________________ Carl Rechsteiner, Bladesmith Georgia Custom Knifemakers Guild, Charter Member Knifemakers Guild, voting member Registered Master Artist - GA Council for the Arts C Rex Custom Knives Blade Show Table 6-H |
Tags |
5160, art, bee, blade, blades, easy, edge, etching, handle, heat, hot, knife, made, make, quenched, stabilizing, steel, temper, throw |
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