novam1a Posted January 18, 2017 Share Posted January 18, 2017 i was tempering a couple of bowie knives after hardening them last night and left them in the oven on 400.(have alot going on) any way is everything ok or do i need to re harden them? Quote Link to comment Share on other sites More sharing options...
C-1ToolSteel Posted January 18, 2017 Share Posted January 18, 2017 Are you saying that you left them cooking at 400 all night? Quote Link to comment Share on other sites More sharing options...
Tubalcain2 Posted January 18, 2017 Share Posted January 18, 2017 if so they would be way too soft. Quote Link to comment Share on other sites More sharing options...
JHCC Posted January 18, 2017 Share Posted January 18, 2017 Tempering O-1 at 400°F for two hours should give you a Rockwell C hardness of 62.5. Not sure what effect a longer tempering time would have. Quote Link to comment Share on other sites More sharing options...
Steve Sells Posted January 18, 2017 Share Posted January 18, 2017 test them, they should be fine unless they were straight razors; then you may want to re harden and temper at 325F 1 hour ago, Tubalcain2 said: if so they would be way too soft. Where do you get that idea? Please site sources. Quote Link to comment Share on other sites More sharing options...
swedefiddle Posted January 18, 2017 Share Posted January 18, 2017 Good Morning, Length of time at the temper temperature should not affect the product. Listen to Steve. Neil Quote Link to comment Share on other sites More sharing options...
Tubalcain2 Posted January 18, 2017 Share Posted January 18, 2017 26 minutes ago, Steve Sells said: test them, they should be fine unless they were straight razors; then you may want to re harden and temper at 325F Where do you get that idea? Please site sources. I guess this must be a misconception of mine. I had thought that the longer it was tempered for the softer it would get. is that not the case? now that i think of it, i don't know were i got that idea, it has just been something i have always assumed. thanks for calling my bluff. Novam, disregard what i say and listen to Steve. he's the expert, i'm very much not. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted January 18, 2017 Share Posted January 18, 2017 There a time at temp factor but it's more like years and so doesn't factor in most uses. Cycling makes more of a difference faster to deal with processes that are statistical based. (you don't get 100% change but a high percentage...) Quote Link to comment Share on other sites More sharing options...
JHCC Posted January 18, 2017 Share Posted January 18, 2017 Think of it like cooking a steak. If you don't get the internal temperature above 140°F, it will never be any more done than rare. So, if you put the steak in a vacuum bag and immerse it in a circulating water bath held precisely at 140°F, you can keep it there all day long without it hitting mid-rare. Quote Link to comment Share on other sites More sharing options...
Tubalcain2 Posted January 18, 2017 Share Posted January 18, 2017 gotcha. thank for explaining. Quote Link to comment Share on other sites More sharing options...
novam1a Posted January 18, 2017 Author Share Posted January 18, 2017 guys, thank you very much for your help Quote Link to comment Share on other sites More sharing options...
will52100 Posted January 19, 2017 Share Posted January 19, 2017 Test them. I've found with the steels I use and either my toaster oven or my Paragon, if I do three, 2 hour temper cycles I can use a lower temp and still maintain flexibility. I don't KNOW that you've softened them, but they would be suspect until tested. The brass rod test will tell you more than any rockwell tester, and a cheap Radio Shack pocket microscope to inspect the edge is handy as well. I don't necessarily think it's the temperature and time alone that is the issue, more likely the cycling of the oven. In my toaster oven I have a 3/8" thick chunk of plate to hold heat and even out the temp swings. Both it and my Paragon run full blast until set temp is reached, then cycles on and off at full power to maintain the temp. Neither oven is perfect about maintaining temp, both rise and fall a little, and that may be what's causing the blades to be softer the longer they are in the oven. Long winded way of saying, sharpen and test, if the edge stays flexed during the brass rod test, you need to re harden. If it chips, raise your tempering temp a bit and re test. Also, if you have a fairly thin edge to start with, you might want to take a little off before testing as the thin section gets hotter quicker and may have tempered more. Quote Link to comment Share on other sites More sharing options...
Steve Sells Posted January 19, 2017 Share Posted January 19, 2017 may have tempered MORE ???? Quote Link to comment Share on other sites More sharing options...
will52100 Posted January 19, 2017 Share Posted January 19, 2017 Kinda doubt it needs more tempering. Just saying, test the edge. I do that anyway on every one even if I'm 100% sure of the heat treat. Quote Link to comment Share on other sites More sharing options...
templehound Posted January 19, 2017 Share Posted January 19, 2017 2 hours ago, will52100 said: I do that anyway on every one even if I'm 100% sure of the heat treat. Good boy!.....Likewise! Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted January 19, 2017 Share Posted January 19, 2017 and *NEVER* trust an oven's temperature gauge! They sell temp gauges at cooking stores as cooks don't trust them either! Quote Link to comment Share on other sites More sharing options...
will52100 Posted January 19, 2017 Share Posted January 19, 2017 Yup, even with the Paragon I use a temp gauge, and for sure use one on the toaster oven. Even so, still test the edge. Quote Link to comment Share on other sites More sharing options...
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