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06-21-2016, 11:41 AM
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re tempering
hey guys..so ray we spoke about this the other day but i figured i would put up a post and see if anyone else as the answer to this (give you a break from all my questions but chime in if ya want)....has any one had to re temper any knives... i just grinded and sharpend a knife to do a brass rod test. i tested this one first because it was HTed in a batch of blades. so this one is deffinitly too hard major chipping on the edge... should i just re temper a little higher as it is? i am using the even heat oven to do this i didnt know if i should grind off the sharpened edge first and if so how much to grind off...i thought about this because i thought maybe since the edge is sharpened (and thinner) it might get hotter than the rest of the blade and mess with the results from the next brass rod test after its re tempered? any ideas??
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06-21-2016, 12:10 PM
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If the blade is too hard you can re temper it at about 25? F higher until you get the proper brass rod test. If you ever get your blade too soft there's no choice but to start over with austenization and quenching. When you have the hardness the way you want it all you need do is grind out the chips from the edge.
Doug
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06-21-2016, 12:12 PM
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Ray or one of the others can chime in here with more detail, but I always heard that you should just throw them back in the over for another session and jack up the temperature another 25F or so.
The temper process is a matter of holding the steel at a fixed temperature for a fairly long period of time - letting it "soak". The entire blade will get to that uniform temperature in a relatively short period. Therefore you do not have to worry about the edge getting hotter than other parts of the knife. There is no need to grind off the entire edge in advance, except as needed to repair the areas where it chipped or cracked.
-bill
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06-21-2016, 01:43 PM
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Them fellers done said all that needs sayin' ....
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06-21-2016, 01:45 PM
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Ok thanks guys yeh i was worried that maybe since its alreay sharpened it would be so thin maybe that thin edge would soak up more of the heat and get softer than the rest giving kinda a flase test .....i dont know if that makes sense it does in my head but my head doesnt always translate to keyboard right either way i am goinng to go try re tempering now thanks!
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06-21-2016, 04:16 PM
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Where grinding the edge too sharp causes a problem is where the blade is too soft and you have to re-harden it. The difference in quenching the fine edge and the thicker spine can cause warping in the edge resulting in something resembling a potato chip. If you are going to make a mistake in tempering you want to temper too hard and then walk the hardness back.
Doug
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06-21-2016, 04:50 PM
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yeh thats what i did i HT a batch of blades i think 9 because i dont have a dewar for the liquid nitrogen and the container i put it in it only last 2 days before it evaporates....so doing them in batches seems to be the only way to make it worth mile money wise....the last batch i did wasnt as many but i think i right temper is somewhere around 375 so since i cant leave the blades in the liquid nitrogen longer than a day or two and if i took them out and didnt temper then i risk stress fractures so i tempered them all low figured i would work my way up till its right i just didnt know if the edge affected the re temper.....what about edge geometry would that efffect the brass rod test too ya know if you made the secondary bevel (that get sharpened) with a low angle you would get a taller skinnier bevel if you do a high angle you would get a shorter thicker bevel i try to keep it somewhere in the middle anyway ...just something i was thinking about
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06-21-2016, 05:13 PM
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If the edge is too thick to flex then the brass rod test might not be of much use...
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06-22-2016, 08:15 AM
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thats what i was getting at i try to keep in somewhere in the middle and it usually lands somwhere in th middle of what you can do when sharpening with the edge pro so i think it should be good
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art, back, blade, blades, brass, edge, fixed, grind, grinding, harden, heat, hot, knife, knives, make, post, repair, rod, sharp, sharpening, steel, temper, throw |
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