thunderforge777 Posted August 21, 2012 Share Posted August 21, 2012 i was hardening a bowie knife i made today. i made it from 5160 spring steel. i heated till it was nonmagnetic, then i quenched it in motor oil. i noticed it was a little warped and bent after the quench but i didnt see any cracks. i put it on the anvil to straighten it out a little and bam it broke in half. i didnt even hit it that hard. what did i do wrong? Quote Link to comment Share on other sites More sharing options...
Steve Sells Posted August 21, 2012 Share Posted August 21, 2012 you hit it Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted August 21, 2012 Share Posted August 21, 2012 When it comes out of the quench and is cold it is as brittle as glass NEVER DO ANYTHING UNTIL AFTER TEMPERING! I had a student who left a blade on his workbench after quenching as it was too late at night to temper---came back in the morning and it was in 3 pieces just due to the quenching stresses. TEMPER IMMEDIATELY! If you do a differential temper You *might* be able to straighten a slight bend; but in general a bend requires reheating to straighten and then repeating the heat treatment---which is actually often a good thing metallurgically. (there are situations with some alloys where you can straighten before it cools all the way down from a quench---but it's always a risk!) The answer to the base question "what did I do wrong?" is: you didn't know what you were doing *before* you tried a tricky thing like blademaking. Why we suggest folks *learn* the basics before trying the graduate level skills. I mean you had practiced heat treating on similar shapes and alloys before doing the knife right? Quote Link to comment Share on other sites More sharing options...
thunderforge777 Posted August 21, 2012 Author Share Posted August 21, 2012 ok thanks for the info. i learned my lesson on that one. so if i quench a blade and it warps again....should i temper, then reheat and straighten and then harden it again, then temper again? Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted August 21, 2012 Share Posted August 21, 2012 I'd skip the temper and put it right back in the forge in that case; but a temper never hurts! If your forge has a limited hot spot I might temper first to prevent more stress as only part of it gets heated at first. BTW did you normalize several times before hardening? Quote Link to comment Share on other sites More sharing options...
Steve Sells Posted August 21, 2012 Share Posted August 21, 2012 did you read what I posted on the process of heat treating? http://www.iforgeiro...-stickies-here/ the how what and why is explained there. Quote Link to comment Share on other sites More sharing options...
jmccustomknives Posted August 22, 2012 Share Posted August 22, 2012 LOL! :lol: Reminds me of my first attempt. I made a machette out of a car spring, built a big fire and quenched it in a bucket of water. I wasn't happy with the shape so I started grinding on it and,,, :o it uncerimoniously broke in half. Learn the soft back draw/and or edge quench. If you get a little warp you can usually straiten the blade after its tempered. Quote Link to comment Share on other sites More sharing options...
Aden Cassidy Posted August 27, 2012 Share Posted August 27, 2012 (edited) Only broken a couple that way, am mostly self taught apart from the club I am a part of. Been there since I was about 13 yrs old. Broke one recently, it was one that I tried to make really thin. used spring steel. Had another file I used the other day that was broken, drew it out and thinned it down a bit. If I hadn't it would only have a 1 1/2in or so blade. Best I have hardened, First file I hardened.Kept on thinking it would break. Plenty left to break when I try other steels and blade styles later on. Bet we all do, even the experienced blokes. Can't seem to get the pictures right when you click on them though. Edited August 27, 2012 by Aden Cassidy Quote Link to comment Share on other sites More sharing options...
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