overmodulated Posted July 18, 2009 Share Posted July 18, 2009 Folks: a couple of questions before I risk inadvertantly destroying another knife. (I'd try to answer these questions on my own through experientation but I don't have a forge in my own house, and have to pay for limited forge time at a local educational smithy.) I have an approx 15 x 3/8" blade hammered out from a RR anchor clip. (One gentleman on this forum suggested it's simple steel in the vicinity of 1060-80). I'm going to attempt to quench this with quenching oil in an aliminum roasting pan (like what you'd use for a turkey). 1. Would there be any problem laying the knife on its side at the bottom, or does the oil need to flow freely on each side? 2. Does edge quenching introduce greater risk of cracking at the edge than full immersion in the oil? (I ruined my last piece of work while edge quenching.) Thanks for any insight! Quote Link to comment Share on other sites More sharing options...
overmodulated Posted July 18, 2009 Author Share Posted July 18, 2009 Pardon my duplicative post under Heat Treating, General discussion... Folks: have several questions before I risk inadvertantly destroying another knife. (I'd try to answer these questions on my own through experientation but I don't have a forge in my own house, and have to pay for limited forge time at a local educational smithy.) I have an approx 15 x 3/8" blade hammered out from a RR anchor clip. (One gentleman on this forum suggested it's simple steel in the vicinity of 1060-80). I'm going to attempt to quench this with quenching oil in an aliminum roasting pan (like what you'd use for a turkey). 1. Would there be any problem laying the knife on its side at the bottom, or does the oil need to flow freely on each side? 2. Does edge quenching introduce greater risk of cracking at the edge than full immersion in the oil? (I ruined my last piece of work while edge quenching.) 3. Is 1 gal of oil enough for a blade this meaty? Thanks for any insight! Quote Link to comment Share on other sites More sharing options...
Rich Hale Posted July 19, 2009 Share Posted July 19, 2009 Not to be short but I suspect you know the answers to all of the above..your failed attempt is a point to the correct direction. Have you read all the site has to offer on heat treating? that is a must if you are gonna heat treat blades.. Quote Link to comment Share on other sites More sharing options...
overmodulated Posted July 19, 2009 Author Share Posted July 19, 2009 Sir: I believe I read most of what the site has to offer on this, beginning with the basic and advanced heat treating stickies. I didn't see clear answers to these questions - perhaps I asked them with a little different twist. What I gleaned is that the RR clip I forged is 1045-1060 (rather than 60-80 as stated above), and this steel is in the mid-high-carbon range. Some quench with water, some with oil. No one suggesed a particular recipe or ratio for quenchant volume based on blade dimensions or mass. I learned that edge quenching is responsible for the bow of many swords (katanas), but would also guess that this kind of stress makes it more prone to edge cracking. I would also imagine that if this quench method significantly increases the odds of failure then it wouldn't be as popular as it is, because the spine can be softened other ways. I've seen your work and am impressed. I've ony made a handful of knives so far (mostly primitives) and would therefore greatly appreciate your insight here. Thanks! Quote Link to comment Share on other sites More sharing options...
Rich Hale Posted July 19, 2009 Share Posted July 19, 2009 See if bp0078 has wot you need. Quote Link to comment Share on other sites More sharing options...
nonjic Posted July 20, 2009 Share Posted July 20, 2009 Im not mega experienced, but have read a bit, and tried a few things. Its worth having plenty of what your quenching in so you can imerse the blade vertically (straight down) into the medium, this helps keep it all even and prevent warpage,. The basic rule is start with a slow quenchant (oil) , if it doesnt harden then water, if still no joy iced water, then brine, then iced brine! I would have thought that oil would be fine for .4 carbon, but without knowing how you forged it (ie how many heats, how hot you got it, ie how much carbon youve lost) its hard to say. I get best success with hardening blades if Ive done all the prep work properly, ie tripple normalised to reduce the grain size, and a good finish on the blade (400 grit hand rub) (no stress raisers). I paint the blade with a slurry of fire cement before heat and quench so ive still got a nice 400 grit hand rubbed finish (pretty well) after quenching. Worth remembering that you might have a decarbed skin on the outside of the blade after quench that the file cuts easily, but the core of the blade has hardened. worth checking it properly before re-quenching in a faster medium, guess how I founf this out hope this helps a bit, but like I say im very much still finding my own way on this subject! Quote Link to comment Share on other sites More sharing options...
overmodulated Posted July 20, 2009 Author Share Posted July 20, 2009 Rich: the blueprint is informative but didn't offer quenchant volumes or even a rule of thumb. John: great - thank you. Fire cement? Haven't heard that before, only clay. Do you leave just the edge exposed? Is it easier to knock off the cement after quenching than the carburized skin to get back to smooth finish? Quote Link to comment Share on other sites More sharing options...
nonjic Posted July 20, 2009 Share Posted July 20, 2009 (edited) I buy the pre-mixed fire cement from a diy store (its like a putty consistency, Might be called XL fire cement ?) its used for patching fireplaces, and I use it to patch the forge lining. I take a pinch of it, and mix it with a little water with a paint brush untill it is a watery slurry (milk like consistency), then paint a very thin coat EVENLY over the blade before heating, when you quench it pops off anyway, so a very light sanding to remove the residue before tempering puts you back pretty well where you were finish wise before H.T The coating on the blade is probably only a few thousanths of an inch thick. Its one I thought of myself, but im sure others have been doing it for years ! If you have any paint brush streaks in the slurry after youve painted it on you can sometimes see a very slight hamon (differential hardening) finish in the blade after polishing, again, ask me how I found that out edit, .... yes, I paint the whole blade, handle, edge n all with the slurry,.. Heres a link to the stuff I use, its cheap as chips, and does a brilliant job of patching up the forge aswell http://www.plumbworld.co.uk/xl-fire-cement-2kg-172-241?CAWELAID=205022606 Edited July 20, 2009 by John N Quote Link to comment Share on other sites More sharing options...
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