At what temperature are YOU termpering O-1 blades?

L

loosenock

Joined
Jul 10, 2002
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Ive been puttering around making and forging blades for about a year now. When I first started I read everything I could possibly read about heat treating. By reading, through experience and destruction testing of my blades I think I could classify my knowledge as "some". I have been tempering O-1 blades at 425 to 500 depending how hard I wanted it. That gave me R58-59 give or take. Recently I read Pete Hamiliton's "The Randall Chronicles" on page 21 where Randall tempered their carbon and stainless blades at 572 degrees overnight. According to which chart you read this makes there knives about R54-R56. Having a nice Paragon oven, my last blade I brought up slowly to 1480 degrees soaked there for about 5 minutes and quenced in 125 degree oil...just like randall. Then after sanding on 200 and 400 grit belt I returned the blade to the oven and did a 2 hour temper at 572 degrees. The blade looked like it had been blued like a new riffle. After final sanding and polishing I honed it a bit. It felt really sweet honing. I think I might try this for a while.

So my question. What temperature do you temper your O-1 blades at? And if you care to elaborate, why?

Thanks

Joe
 
I usually temper them at about 375,
I do this because in my testing this gives the hardest edge that still passes my toughness tests. I sometimes temper at 400, or 425 for bigger knives, I usually make small utility knives and hunters.
Kyle Fuglesten
 
This is a very timely thread because this last week I found some AISI O-1(3/8"x 2 1/4" stock) at the local scrap yard and just forged a piece for testing. It just came out of the oven from it's second temper. I tempered at 380 degrees after a triple edge quench. It's going in the freezer overnight and when I get home from work tommorrow it'll get it's third temper. Then it gets tested and broken so I can see whats going on in there.

I hope more folk chime in here with their recipes. I now have quite a bit of this steel and knowing how others work it is really helpful.
 
400 degrees, for two hours. 2 or 3 cycles.
I heat treat with a heat shrink torch and temper with the oven in the kitchen so things aren't really precise but I do keep things consistent. Judging from the way they sharpen on an arkansas stone I'm at least RC60. Haven't had any problems with chipping though, and I have one knife I've really beat the hell out of. Everything short of a full flex/snap test.
 
2 hour and a half cycles at 370F, rock well testing shows 57 to 59. This passes the brass rod test every time for me.
 
O1 is the most fun steel I have worked in my short time with knife making. I love it as a functional knife steel but dislike very much how it so quickly discolors when only breifly washed.

Tomorrow, because my lady wants me to go to bed now - and I like that, I will post here on this thread (once again) a killer HT recepie for O1. You must be able to see the the shadows during HT though, all lights must be turned off and shades drown during HT. I shall explain, as taught me by Tim Zowada. - Tomorrow - again, and tempering will be included.

O1 may be one of the best of the retentive steels.

Roger
 
Heat to 1475 F. As the steel austinitizes, If you watch carefully you will see one or more shadows in the steel. I call these ghosts and what you are seeing is the steel actually austinitizing. They appear to look like cold spots. They are not. They should also appear to move about the blade. You do not need a magnet for testing. When the ghost(s) finally disappear pull the steel - at that point and do not be more than a few seconds late in doing so. Quench in a manor so as to cut the oil in a back and forth motion, NOT side to side. Quench for approximately 7 seconds. When the blade is pulled the oil on it should smoke but NOT flame. If it flames quench another second or two. Try to pull the blade when it is about 350 to 400 F. (it smokes). The quenching oil should be pre-heated to about 140 F. so as not to over shock the steel. After quenching grip the end of tang in a vise and let 'still air' cool to no less than 125 F.. Simply laying the steel upon something prevents the steel from cooling uniformly.

I first snap temper once at 50 F. lower than I temper. I have been tempering at 375 F. It is vital that you temper (snap or regular) before the quenched steel falls below 125 F. but should not be greater than 150 F. So, have your temper oven pre-heated before quenching. I do three tempers, not including the snap temper. Although I have not yet done this: the second and third tempers may be best performed about 25 F. lower than the first temper. This may better preserve the original RC of the first temper (not talking about the snap temper here).

It is probably best to multiple quench and if cry-ed do it after a snap temper.

Roger
 
heat till its orange (more on the orange than cherry), quench in oil, temper in the oven till its golden yellow. Your done.
 
Not to make fun but sometimes it seems on some of these threads this process is made to be so complicated. Heat treat some stock and break it, observe the grains. If they look silky grey and matte finished your doing ok. If you get the steel to hot you will see it in the grains if a file doesnt touch it, its hard. With all the info that is out there you cant go wrong. The bottom line is you have to play with it and find what works for you.
 
One more thing after re-reading your thread if you got a real nice blue color that is way too hot unless you are making springs. Your blade is going to be in the mid 40's for Rockwell. Great for a spring but poor for a knife unless your shooting for a wire edge sharp. you want a rich yellow golden color that will put it around 58/60 or so. But with that you do want a selective hardening especially with a long blade. Find some color charts for your tempering. It will work and is right on the money.
 
I am the first one to admit that there is a whole world about heat treating knife blades out there I need to learn. I also sit in humble respect to everyone who makes knives. I think that the road to knowledge is to ask questions and have discussion. I hope that no one takes offense to my following comments, they are in no way directed to arguments.

I have several printed sources stating that 570 degree temperature will yeild about R55-R57 hardness on O-1 steel. One newly purchased piece of O-1 had treating instructions on printed label attached to the wrapper stating a temperature of 800-850 degrees will produce hardness of R48-R50. I dont know what temperature you would have to go to have for mid 40's rockwell.

I currently own two Randall knives, one old and one new of same material and model. In the past I have owned 4 others of both carbon and stainless blades. On none of these knives have I ever detected a wire edge developing during sharpening.

It can be argued about Randall knives being the most collected and respected knife in recent history. I think they make a fine knife that is affordable for anyone who really desires to own one.

My personal experience. When I temper a blade at a light straw color (400-425), I have a hard time sharpening with diamond sticks.

My next question. Who believes Randall knives are too soft at their tempering with temperature at 572 degrees?

Joe
 
First off I didnt want to offend anyone at all. It just seems at times that something simple is made rather complicated. The colors I referred to are for simple carbon steels. Perhaps Randall is using 52100 or something else.http://www.pvsteel.com/docs/Tsb-112.pdf Here is a heat treat chart and here is a color referance http://www.tpub.com/steelworker1/11.htm These arent the best link but are examples of many. Yes the steel will be harder to sharpen because the steel is harder so the edge will last longer and be resistant to abrasion. These color charts are for simple steels and O1 is at the limit of of this. The 10 series would be a better example but the colors still apply to this.
 
Blackboogers,

Certainly no offence taken by me. Diversity of opinion permits improvement.

I would be concerned though (and I know you did not advise doing this) about tempering tool steels in the 500 to 700 degree F. range. Brittleness, you know. Probably not dangerous for knife blades but could cause easy breakage.

Roger
 
I make lots of hardcore hunting knives from O-1. I single edge quench and then do a full temper at 375-385F for 90minutes(my oven is never that precise). Followed by a deep freeze for 48hours. Followed by a destress at 325F for 1 hour. I have tried more (eg.- 3) tempering cycles with and without a freeze cycle in between and found the gains to be limited once a single temper and single freeze cycle was done. I have tested my blades at a local HT-er at 60-61HRC at the edge with tempers at 375F. The freeze consistently mikes out 0.5HRC higher in hardness. There is a small amount of difference in use with edge holding and wear resistance when doing finishing grinding with the freeze.

The issue of tempering softer eg,.- down to the mid-50's is apparently for toughness. BUT ... consider that lots of guys using O-1 will do differential HT's anyway and O-1 is already prety tough, there is an argument that there is no need to use anything less than the maximum "working" hardness. With maximum "working" hardness, I mean the 59-61HRC range. I made a simple tomahawk head of forged O-1 stock tempered to 56HRC (about 500F) and another one tempered to 59-60HRC (about 400F). I have taken an entire lemon tree apart with the harder tomahawk blade - it has never chipped, broken etc. and it simply held its edge longer than the softer one.

My argument is that there is little to be gained by going too soft and too much to be lost. I must qualify that my ideas apply to selective hardening O-1, flat grinds, slightly convexed edges. Cheers. Jason.
 
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