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Main Boards => Hunting Knives and Crafters => Topic started by: agd68 on January 05, 2009, 01:43:00 PM
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Hi All,I've made a few knives now and it seems to be working out.I'm using some old sawmill blades. I heat the blanks up in a wood stove until red hot,let cool overnight in the ashes to anneal,heat to red hot and quench in old motor oil to harden and temper at 350 for 1 hr in an old oven.Kind of primitive but seems to work.If I'm doing anything wrong please let me know. I've read that some of you temper more than once in the oven.Is this better? How many times? Is it better to temper the blade fresh from quenching or does it matter if it cools down?
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Your on the right track. The basics are good. I would increase the draw back time by 15-30 minutes. I like for the oven to have time to come up to temperature and then at least a full hour at temp. I do 1 hour and 30 minute draw. The actual temperature depends on your steel. If you are having success, I would not change much.
For real hard use knives, such as chopping, filet, etc, where the blade will undergo a lot of flex, shock, or stress in it's normal use, I draw back twice or three times. In other words, knives of any size over 4-5 inches. Some just go ahead and draw the blade multiple times on all of them. It's a good practice. I have to assume the knife will be used hard. Lin
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Thanks for the info Lin. The ones I make now are pretty much all under 4" blade.If I have it right,the multiple tempering allows for a more flexible blade? How long do you wait between tempering sessions ?
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There you go using knifemaking terms. I would say tougher blades. Flex can be determined by a couple of things, the steel's character and thickness. Flex implies that it will return to the blades original straightness. It certainly should do that. Toughness might mean it can flex many more times without any problems. It can get confusing even for knife nuts.
Help me out Karl! :help: :wavey: Lin
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Got it. Thanks.
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From what I have learned, it is best to do at least 2 tempering cycles for 2 hours each to be safe.
Start on the low side with your temps, if it is too hard, you can raise the temperature to get it where you want. If you start too high and the blade is softer than you want, you have to harden all over again and then start lower on the tempering temp.
I have had it happen to me both ways, and it is way easier to put a too hard blade back in the oven, than to try to re heat treat an essentially finished blade!
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I'll tell you what is difficult sometimes to REALLY get your head around:
It often seems that many concern themselves, and get really focused on,"TEMPERING". Sort of thinking that if they temper their blade at this temp, and do it this many times for this long, then they'll end up with "X??X" hardness.
For ANY of those tempering "recipes" to predictably work correctly, and function along with industry standard proceedures, the steel must have reached FULL HARDNESS to begin with! All of those tempering times and temperatures have been determined by utilizing them on FULL HARD STEEL. This of course requires proper treatment up to the full hardening process with correct temperature control and steel/alloy heat treating procedures to begin with.
Sort of like saying that if you do not have your steel type up at the right temp, (not to high - not to low) -)for the proper amount of time, and then quench it in the correct medium to extract the heat at the proper rate FOR THAT STEEL to transform the austenite into martensite, then it doesn't matter how you temper it!
See what we're up against?
So, that behooves the knife maker to use the simplest steel that he can control with the equipment he has.
For example, 1084 is about the simplest steel going. If you get it non-magnetic and quench it in something wet, it'll get hard. How hard? Depends on the control of your processes up to that point.
If you harden something that you have overheated earlier, without going through post forging normalizing steps, and grain reduction steps, and then you harden it - you've got junk.
If you don't get it completely up to the temp for THAT steel, and quench it in the correct medium at the correct temperature for that steel, regardless of all the other steps being in place, it won't get hard!
Tempering is the easist of all the steps to accomplish.
Grain size, even carbon distribution, post foring techniques, proper temps and times for THAT STEEL, etc., are the hard parts.
Without those in place, tempering is just wasting gas and electricity.
I have found Lin to be a really good teacher, and he is one of my heros! Like he says, flex is, for the most part, determined by geometry. It's where the flex FAILS, and blades break, that is determined by heat treatment.
Which brings up another point!
Terminology.
"Heat treatment" begins at the mill, and ends with the final tempering.
Everything done between those two points can/will/might change the chemistry of the steel. That is all the "heat treatment". Simply said, anything that treats the steel with heat, is heat treating - milling, forging, normalizing, thermal cycling, annealing, hardening, tempering - are all one looooooooooooong heat treatment.
It's always easier to discuss these processes if all concerned use the term to describe the step/action.
That's all the bad news.
Good news is, steel is easily obtainable to match the maker's experience level.
I have been using my torch a lot lately, over the last few years, on my hunting sized knives.
The post I made a few weeks ago where the guy said he took 5 deer from "field to freezer" before he touched up his blade, was done with a torch.
Anybody can do it.
But! That steel was properly treated up to that point with concern to really watching forging and post forging steps for grain size and carbon distribution.
Why am I typing all of this and gettin' people mad at me? 'Cause I've got two blades in the oven just about done with their last tempering cycle and I've got some time on my hands.
When you get a steel up to the temp at which it is prescribed to be quenched, the steel is in the condition called "austenite". When you quench it, it transforms into a condition known as "martensite", which is the hardest condition of steel. But, it's also under a lot of stress and is quite brittle as a result of changing into a new structure.
However, ALL of the austenite does not make the transformation, and is known as "retained austenite". It is RETAINED in that condition.
When you do that first tempering cycle, on full hard steel, you are moving the "retained austenite". There was "left over" "stuff" that didn't get to transform into the "hard stuff" because the cooling process of the quench stopped it from occuring. As well, that first tempering cycle relieves stress, and some of the brittleness, created by the steel that DID make the transformation.
Now, since the "retained austenite" was able to make the transformation during the first tempering cycle into martensite, we need to relieve the stress created by its completion -hence, the second tempering cycle.
So, if you feel you've done a good job getting your steel hard in the first place, always give it two tempering cycles at the temp for that steel.
Almost sounds like I know what I'm talkin' about, but, for the most part, I've spent just enough time to learn the terms that define what I've been doing.
When I look at the graphs and photo-micrographs of steel - I'm a complete idiot. I haven't got a clue what they mean.
There are some really neat demos that can be done with steel, and I might do some photos that will show some of these. Just takes time.
Take an old file sometime, wrap it with tape, and bust it in two with a hammer. The tape keeps it from flying all over the shop like shrapnel.
Look at the grain. It's visibly fine and tight.
Now, get it TOO HOT and hold it there for a minute or so. By TOO HOT, I mean really yellow - yellow orange. HOT!!
Then quench it really quick in some warm oil.
Break it again.
The grain will be VISIBLY coarse and "grainy". Not good for a knife. If you get your steel too hot before you quench it, or right at the end of forging, and fail to do grain reducing steps, you've got junk.
Now, take the file, get it just above non-magnetic, the next color change above non-magnetic, and let it cool back to black. Do this three times.
You are reducing the grain size.
This is what you should do after forging your blade. It sort of "corrects" your forging errors.
Now, get that file just back up to barely above non-magnetic and quench.
Break it again.
The grain will be back to fine!
Easy demostration that what we are doing with time and temp effects the steel - either good or bad.
I'll give you two things I've heard over the years,
"Jesus Christ, Himself, could send a bar of steel down from Heaven. It'll only be as good as the heat treatment it gets."
and,
"The most a blacksmith can ever hope for is to end up with as good a piece of steel as the one he started out with."
Simply stated, we have far more opportunities to ruin good steel , than we have to improve it.
Anyway, have I gone on long enough?
You probably weren't expecting that Lin.
Sorry.
Everybody's probably mad at me now.
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Dang Karl! Did you take a breath? LOL! Mad at you? Nah...still deciphering! Nice to have the pros on here for the technical stuff!
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Don't confuse me with a "pro"!
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Here's something else to confuse it all even more:
"Critical" is NOT the same as "Non-magnetic".
Critical is that temp at which all of the carbon and the alloys go into "solution". Solution, sort of meaning they (all of the alloys and the carbon and the iron) sort of dissolve into one anther and become atomically "liquid" for lack of a looser term. They all sort of become detached from sharing their spaces with each other. When you get them in this condition and then cool them rapidly (quench) you get hard steel.
If you let the steel cool slowly, all of those atoms of the alloys go back to a "happy" place called pearlite. Soft.
The "critical" temperature of the steels will vary according to the complexity of the alloy content.
Now, "non-magnetic" refers to the dis-alignment/re-arrangement of the nuetrons and protons of the iron atom as a result of the high temperature. That iron atom is the same iron in D2, O1, 5160, 1084, W2, 52100, etc. See what I'm saying? All of those steels will go "non-magnetic" at basically the same temperature, because it's the IRON that's going non-magnetic, and it's SAME iron in all of those steels!
But, the critical temperature, and the TIME that they need to be held at THAT temperature differ from one to the other based on the other alloys in that steel.
A good rule of thumb is to watch the colors of the steel. As you are bringing it up in temp, continually check it with a magnet. As it goes non-magnetic, you will know that you are well into the 14** degree range. But, you're not ready to quench YET! Pay close attention to the color of that steel. Watch that internal "shadow" in the steel. That's a transformation going on from pearlite to austenite. Get that shadow gone and the steel slightly move into the next color range ABOVE the color you saw when it went non-magnetic, hold it there a second, and QUENCH!
If you do that, then your tempering times and temps will have some meaning.
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Karl,
Thanks for the help. I actually understand what your saying. :D I all sounds so intimidating, but after one gets down to the nuts and bolts of heat treating, it's not too bad. I personally had/have to really concentrate to keep the austinite, martinsite, etc straight. For a while I though it was magic. :D
I'm more of a shade tree type of heat treater, even though it works well and I am diligent about things. I try to use very few types of steel, to cut down on head aches.
I do have a question that I have not heard on any other forums. Do you find that some blade shapes accept hardening differently than others? Same steel type, only difference is size or shape. Lin
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Well, it's been pretty easy for me to learn that I just can't get the bigger knives done correctly with a torch when I'm using 5160. I want those done as best I can so I give them a good soak in the oven at 1525 for about 25 minutes.
What has been the single most important factor has been the correct quenchant for the steel type.
I, too, am sticking with only a few steels. 5160, from my 1984 stash, W1 and W2, and 1084. I've only done a few 1084 blades, but, Man! I like it!
That bunch of 1 inch square 5160 I got made back in 1984, will do everything I want ina knife, from small hunters, to big Bowies.
Now, when I use the 1084, W1 and 2, I use the appropriate oil, Parks #50.
5160 gets Texaco "A".
Doug Campbell just sent me some 52100 to play with, and I'm excited about using that.
Anyway, I haven't discovered blade "shapes" acting differently. Now, if that "shape" includes a different thickness, then I think you'll have some variables if you are working with shallow hardening steels like 1095, W1 and W2. With the proper soak at the right time and temp, with a fast oil like Parks #50, those steels will only harden about .125" deep. So, if you are using 1/4" steel, and you consider that .125" from each side, therre will be a small sliver of un-hardened steel in the middle, but this is only at the full 1/4" area, back by the ricasso, so it doesn't matter.
If you are using the deeper hardening steels like O1, 5160, 52100, etc. at the proer soak and correct speed oil, I don't think shapes or sizes make much difference. But, those had better get a good soak at the right temp for full hardness! It's sort of why I like hardening my 5160 hunters with a torch! I find it sort of relaxing. If I get the flame just right, it's almost impossible to overheat the steel, and I can keep 5-6 inches of steel right at the "sweet spot" for a few minutes of soak time. I enjoy that. It's fun.
Is it the BEST? I don't know. there are those that would say "No". But my customers tell me what I want to hear.
I do know that a fellow can't go wrong if he learns just a little bit of temp control and uses the right oil for the steel at hand.
Learn a few forging and post-forging techniques and the knives he makes can perform miracles!! Just kidding.
I'd better not type any more now for a few weeks before people around here start talking about me.
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Karl,
I think you hit on something. The quenchant is probably the variant. Yesterday was pretty cold to start with, so I figured I'd heat it a little extra. I had to quench a couple several times coming up in color each time and still not quite satisfied with the hardness.
I quenched two other blades that were smaller (3 and 3 1/2 inch)and they did great. Lower mass? The bigger, thicker blades were slow to harden. I'm edge quenching these and am wondering if I lower them slightly lower into the oil during the quench, if that will work better. Instinctively, I know that's not right, but Here's why I raise this. I have an 8 inch blade, I quench, the front half get harder than the back near the ricasso. I think this is because it is deeper in the oil and loses heat faster because of being relatively thin and low mass.
I also think because I heated the quenchant a little extra, it would not tranfer the heat fast enough in the thicker parts of the blade such as where the choil drops from the ricasso.
So, instead of trying to dip the blade lower, I should heat the oil a little less before quenching.
Again, this was a problem on my medium and larger blades only. In your experience, how does the temperature of the oil relate to your blades ability or inability to harden? Lin
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You know that hot oil extracts heat from the steel faster than cooler oil - right? Of course, you do. The hotter the oil the faster it circulates around the surface of the steel.
But then again, what oil are you using?
The "proper" quenching oils - and I'm not just saying this lightly, I'm pointing it out for everyone following this thread - the proper quenching oils have additives that inhibit a vapor barrier from being created between the steel and the oil, thus resulting in no cooling occuring, because the steel is not in contact with the oil! Then, you miss the hardening segment of the quench.
That's why oils like veg oil and mineral oil, etc. don't achieve the best hardening. I'm not saying they won't work. Many people have used them. They just aren't the best! They lack the additives that eliminate the vapor barrier that occurs when you stick a piece of steel in it that's 1500 degrees!
I've read that even the really high dollar quench oils are ESSENTIALLY mineral oil, it's just that they also have the "secret" additives to eliminate the vapor barrier.
I have most DEFFINITELY experienced harder and harder steel the warmer I got my oil!
Deffinitely - without a doubt!
I used to quench my 5160 at about 135, but am now right where Ed Fowler says to be - 165.
And guess what - they're harder than they have ever been. Ever.
Here's another factor, and that is the AMOUNT of oil you are using!
When you are quenching a small hunter, and here you are correct about the amount of mass, it doesn't really take all that much oil to get it hard.
But! When you're doing a 10 inch long, 5/16" thick Bowie, that's another issue! That's a LOT of heat to extract.
We've got to remember that proper quench oils are designed to extract heat at different rates and these rates change numerous times over a few milli-seconds. The heat from that blade can distribute through the oil in only a second or so. So, my point? Use the absolute MOST oil you can!! That eliminates it as a problem.
I welded up two seperate tanks, that are about 8 inches square and 2 feet long, so they hold over five gallons each. That way, there is always enough oil to accomplish what you are trying to get it to do - harden steel!
As well, I make sure that I always have the oil at the right temp, which for me is 5160 - 165 degrees Texaco A.
When I do W1 or W2, I use the Parks #50 at 100 degrees.
When I do 1084, it's such a "perfect" steel, it's almost a cross between a shallow hardening steel and a deep hardening steel!
So, I use the Parks #50 at only about 80 degrees.
Here's another thought!
Some folks quench point down in a tube of oil.
Think of this! That oil extracts heat SO FAST, that as the blade goes down in the oil, the last part of the blade to go in is hitting oil that has ALREADY risen in temp WAAAAAAAAY HIGH from absorbing heat from the first part of the blade to go in!
So that blade is going to have different hardnesses all along its edge.
That's another reason for the big tanks - they are long enough that I can just insert the blade EDGE DOWN right in the oil. The full length of the blade edge is all getting quenched at the same time.
Now, maybe, on that 8 inch blade that got harder on the thinner, front end, it wasn't a matter of the quench hitting different thicknesses, but did you get the thicker areas of the blade up to full temp and fully austenised? Just a thought.
There's so many friggin variables in this stuff.
You're makin' me think too much.
My fingers are sore from typing now.
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Yes Karl I know that the hotter the oil the faster the heat transfer, to a point. I was thinking (maybe mistakenly) that I went over that point. One of the other makers even mentioned not to go a degree over 180. That's what I was refering to, that I may have gone over the top while heating my oil. It very well could be that I need to heat it a little MORE. It was cold and rainy and I may have simply misjudged it. I have another temperature probe that I can use to check my oil and my method for heating it. Once I get the method tweaked a little, I should be fine.
I will say this for all who may be interested. The reason I knew that I had a problem with those two blades is that I test each and every one that I heat treat, with a file to make sure that it gets hard. I cant assume that my methods will work perfectly on every type or shape of blade. It's a thing to remember.
Discussions like this are why I really like the forums. Lin
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Wow!!! My eyes are sore from reading, but don't stop now Karl and Lin. You guys are providing alot of info for us beginning knife makers. Karl explaining the different colors that steel goes through after non-magnetic was helpful. I was heating 01 to non-magnetic then just a little longer and quenching in motor oil. It seemed to work but I'm just beginning. So keep the info flowing I'm personnaly enjoying reading it.
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Well, Lin, you and I both know that sometimes in these discussions, everybody really needs to be on the same page with the same items being discussed or it can be like apples and oranges.
When that "someone" said not to get the oil over 180, what oil was he talking about?
Probably a veg oil or something like that because it would be so hot that when you quenched your steel you'd blow up the garage! Just kidding. Some of these proper quench oils also have additives that give them a very high "flash point" to inhibit combustion.
If we discuss using these times and temps and quenching in industry standard quenching oil DESIGNED to extract heat at a certain rate, and somebody else is using mineral oil, peanut oil, used motor oil, etc. etc., the results just aren't going to be the same.
Guy says, "Well I had my "OIL" up to 145 degrees and my steel was non-magnetic, but it just didn't get hard!"
OK.
His oil was used 10W-40, and his steel was 1095!
Ain't gonna happen.
I have a nice aquaintance with a Master Smith from Montana who had been using another "oil" up to this point in his career. I got him to switch to Parks #50, and he's a new man.
So that's always my very first concern with anyone who is having difficulty getting things like they want - what OIL did you use? And what steel was it?
It's early in the morning and I have my coffee here, so I'll say this once more, 'cause I think I've done it before, for those following this thread, and then I'll shut up.
Some of these steels we use in making knives require different quenchants to achieve the transformation from austentite (the condition it's in when it's up to "temp") to martensite (the good hard condition!).
The different alloys in the steel change "things" during the quick cooling process. Imagine it sort of like a whole bunch of "stuff" getting in the way of the iron and carbon trying to form a new structure - martensite.
The more "stuff" (the alloys) in the way, the longer it takes for the steel to create martensite. It needs to push all of this stuff around and include it, as well, in the new structure. Some of these include O1, 5160, and 52100.
Then, there are some alloys like 1084, 1095, W1 and W2 that have alloys in such an arrangement and percentage, that they do not restrict the iron and carbon very much, so that the steel can create martensite VERY QUICKLY!
So the extraction of heat from the steel must match the alloy content of the steel.
To get really specific, in the first set of steels, O1, 5160, 52100, that steel needs to get below about 1000 degrees or so, down from 1525-1550 in about 5 seconds. So the additives in Texaco A, Parks AAA, Brownell's Tough Quench, are designed to extract the heat at that RATE.
If that steel does NOT get below that 1000 degrees or so in that many seconds, the steel will try to revert to the soft condition of steel, pearlite, and will NOT make martensite! Some of the oils often used like veg oil and such, do not have the additives in them to inhibit that vapor barrier I spoke of earlier, so the speed of cooling does not occur and the steel doesn't get hard. Oops.
Guy wonders what happened??!!??
Then, in the other steels, because of their alloy content in their particular percentages, they need an oil that will get the steel temp down from 1450-1500 degrees to under 1000 degress in 1 second!!!!!
So, then we use Parks #50 and brine (scary stuff!).
If you don't get these steels under that temp in that time, they don't get hard! They reverted to the soft condition of steel.
So, guys try to compensate for this by heating up their oil, but that only works to a tiny degree if it's not the right oil.
You may get a "skin" on the "fast" steel that's hard, but not the depth of hardness penetration.
Now, on that O1, and I don't know your name, "JMR", the alloys in that sort of require a longer "soak" time at critical temp to achieve the best results. I personally don't use it, for no particular reason, but I know that it would be better if it could be held at about 1500 degrees for 20-30 minutes.
I soak my big 5160 blades at 1525 for as much as 25 minutes.
There is the reverse of this as well - if you quench a steel, say 5160 (a medium speed steel) in the fast oil, it will cool TOO FAST and will crack!
I figure if I'm gonna spend time grinding and forging and sweating and pounding and sanding and cussing, etc. on a bunch of steel, then, rather than have all of my time and resources wasted, I owe it to myself to use the right oil.
It's cheaper to use the right oil.
As well, use the simplest steel I can to match my abilities and temp control.
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I got one of those double burners somewhere long ago, that has two coils on it that I set my tanks on. Then, just a thermometer in it to tell me the oil temp.
Works pretty good.
You're probably right about having the oil too hot. That'll screw it up as well.
Bill Burke told me to get one of those hot water heater coils to put in the tank that also has a thermostat on it and it'll keep your oil exactly where you want it!
I've gone off and forgot I was warming up my oil, only to need to shut it off for a while to let it cool down. That water heater coil and thermostat would eliminate that problem!
Of coure, if we speant all of time we needed getting all of the stuff we should have and doing everything like it's supposed to be done, we wouldn't get any knives made!
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Great stuff here Karl and Lin, thank you!....is it possible that there is a chart somewhere that contains the accurate info being shared here?
Gene
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I don't know of any chart.
But there are books with heat treating graphs for most of the steels mentioned that will tell what the austenising times and temperatures are, temps for annealing, temps for hardening, etc.
There will be graphs that show the time in seconds that the steel needs to go through to create different structures.
Then, you just match the correct oil to that steel.
Here's the way I look at it, sort of an analogy:
I don't think that a race car driver needs to be an expert mechanic to win races. He just needs to know how to drive and do what his pit crew tell him to do.
So, as a knife maker, I don't need to be a metalurgist or a steel "geek" to be able to make a good knife. I just need to do what the "experts" have already determined a loooooooong time ago that needs to be done to get the result I want.
There's no need for me to try to come up with "alternatives" in my heat treating when the proper way to do it has already been created by the industry!
here's one of those graphs and pages I refer to:
the first one shows you the chemistry of the steel, the temps to forge it at, the temps for normalizing and annealing and the temps and methods to harden and temper.
The second chart shows you the transformation times in creating the different structures.
Then, it's up to you, the maker, to somehow acquire the materials and tools needed to attain these temperatures and control them for the appropriate times.
Some steels are much easier in this regard.
(http://i28.photobucket.com/albums/c247/kbaknife/5160-HTG-TTT-001.jpg)
(http://i28.photobucket.com/albums/c247/kbaknife/5160-HTG-p-198-001.jpg)
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Thanks Karl I have thought a lot about this, but now you have given me much more to consider! Good stuff!!
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Thanks again
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OK - I hope nobody is mad at me.
Or confused.
I really, really like this forum - a lot. (It helps that I'm a traditional bowhunter, too!) And everybody here is doing some fantastic work.
Sometimes the creativity overwhelms me.
I just felt compelled to share some of my experiences.
Making knives has got to be about the most enjoyable thing I've ever done. And it aggrivated me to only have infrequent and un-sure results.
I had a coal forge and a bucket of mineral oil. Actually, I made some decent knives! Then I got an acetylene torch for hardening purposes, and my results improved - somewhat.
After struggling along and wondering why this didn't work every time, or maybe changing that a little bit, and get more exasperated, I decided to make a few changes.
Piece of cake!
Overnight, my knife making took on a whole new meaning!
I just started donig what the other professionals were telling me to do!
I built a simple vertical propane forge. I got almost all of the pieces from scraps behind "shops" around town. The body was an 8 inch pipe from a well drilling company. About the only thing I bought was a few plumbing components and a blower. I probably put 70 bucks in it.
Then, after reading what others had posted similar to what I wrote up above, about a zillion times, it became evident that I needed to get the correct oils!
It's not cheap. 5 gallons cost me $75.00.
But that was three years ago and I'm still using the same oil!!!!
After only those tiny changes, and learning just the fewest of simple things, my success in making the type of knives I wanted to, became almost a 100% success rate.
And, on top of that, I KNEW that what I was doing was the right thing.
The confidence that gives a person really made a huge difference.
I in no way intend to change any person's successful actions that they are already confident with. that has not been my intent at all.
I just wanted to share my experiences and success.
The biggest thing I had to do was kick my ego out of the equation and do what the poeple who are a LOT smarter than me were trying to tell me to do!
The steel industry has been around over a century. They've got all types of processes to evaluate and predict and control the steel in making it do what they designed it to do.
And we're using their steel!
Those processes are easily obtainable on a small scale.
I just had to do what they said!
Presto! Repeatable success.
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I just "stole" this info from another knife site that was written by a fellow who really understands a great deal about heat treating and metallurgy.
I was on a discussion about heat treating 1084, and specifically on tempering FULLY HARDENED 1084. I am using NO LINKS, nor am I quoting anyone:
You may notice that (I) often quote higher tempering temps than the usual, "375-400F", stated by many others. In years past, I quoted lower temps. I have done the research and determined that it is counterintuitive to go low for a sharper blade. Sharpness has little to do with hardness, but toughness has a lot to do with edge durability.
The purpose of the temper cycle is to reduce the unstable and overly brittle martensite to a more stable mix of structures. It also is to convert any unconverted Austenite to Martensite. These conversion come at the cost of a small amount of hardness, but yield an increase in toughness, and a reduction in brittleness.
Using 1084 as an example:
As quenched the steel will be Rc64....but is quite brittle.
Tempered at 300F it is Rc 63....and still pretty brittle
Tempered at 400F it is Rc 61-62... and less brittle, but not a huge amount tougher.
Tempered at 450F it is Rc 60-61 and getting a lot tougher
Tempered at 500F it is Rc59-60 and the toughness is rising still.
Tempered at 600F the Rc is 57-58 and it is spring tough.
Now, I don't know about you, but a RC 57-58 knife will get real sharp in my shop. The edge will hold pretty well, and the edge will take a lot of abuse before damage.
For a kitchen blade, which should receive much less edge abuse, is desirable to have a harderer and longer lasting edge,Rc 60-61 will make a top grade chef's blade.
The reason to temper at 400F( or lower) is not really defendable. 500F will get the blade within two Rockwell points of that, again, at the gain of a much tougher blade.
Now, as to time and repition:
The temper cycle is a function of time and temperature. Temperature has a much greater effect than the time, but there needs to be enough time for the conversions to happen. Some of these conversions take an hour or more. So, tempering for two hours is a safe time to use as a standard.
Running a flame across the blade and getting the spine to turn blue ( all done in 15-20 seconds) may well drop the hardness, and it will do some tempering, but it will not replace a proper temper cycle. It takes time to do somethings, and tempering is one of them.
Why repeat the temper if two hours is enough to make the conversions?
The retained austenite that is converting to martensite does not finish the conversion until it gets down to room temperature (actually by the time it gets below 200F is pretty much done). Then it is untempered martensite. It now needs another temper to temper it. On complex stainless steel with high allow contents, it may take three tempers to clear out all the unconverted austenite and temper it.
So a good procedure to follow is to temper on the higher numbers,two hours ,twice. It will work with lower temps and shorted temper cycles....but not as well.
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Lots of great info Karl. I've been using water to quench 52100 for a long time and haven't had any problems with cracking or warping. I always just wiped the edge under to kill the color and then quickly transferred it to warm oil to finish cooling. I bought 5 gal of Parks 50 about a year ago for W2 blades and now I use that at room temp for 52100 also with no problems, just dunk the whole blade under.
I haven't been able to get any Texaco A so I always used motor oil diluted with trans fluid for 5160(I know, not a great idea). I've tried using the P50 at about 70 degrees for the 5160 and I did get a little warping so I'm still looking for some appropriate quench oil.
If you get a chance to compare 52100 blades quenched in Parks 50 vs Texaco A, I'd really be interested in the results.
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Personally, I wouldn't even attempt 52100 in #50. If you are having success - don't change anything.
Parks #50 is "water speed" at room temperature. According to Crucible Steel:
"Oil quench from 1550 degrees F should give a hardness of 67 Rc. Water quenching is said to be risky, introducing too much stress."
So, if #50 is "water speed", ......?
I wish the diagram I have was more legible, or I'd figure out a way to post it. The hardening "nose" on the diagram to achive full hardness looks to abe about 6 seconds to get it to around 900 degrees, and Parks #50 will get it there in around 1-2 seconds. Might be adding too much stress.
As well, the high chromium content of 52100 makes it alittle more deep hardening and #50 and water/brine work best on shallow hardening steels.
But, I have heard of guys doing what you are suggesting, doing a short water quench and then eeeeeeaaaaaaassssssing it in with oil. I just have absolutely no experience with it.
I would use the Parks AAA which is obtainlable and is more suited to deep hardening steels as it has a slower cooling rate.
You won't get any of the Tex. "A" unless you order about 2000 gallons. It's just not made much anymore except for special order.
I know a few guys that have some barrels of it, so I got lucky.
You got warping on the 5160 BECAUSE you used the Parks #50. It's water speed AT ROOM TEMPERATURE.
that's just waaaaaaaaayy to fast for 5160. There's no need to heat it up like is sometimes necessary with other oils.
I think your success with water/oil on the 52100 is cool!!
I'm just not that adventurous.
You're my hero.
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I'm just a backyard hobby maker doing what I've seen others have success with. I started using 52100 after I saw Al Pendray give a lecture about heat treating it various ways at a hammer-in back in the early 90's. That guy seems to have a lot of extra brain somehow stuffed in that normal sized head. I picked up the water wipe thing from watching Charles Ochs demonstrate somewhere but he doesn't use oil to finish, which scares me even to watch.
A lot of what Pendray says goes along with what you typed in that knifemakers tend to try a lot of almost "witchcraft" type made up methods and quenchants when they would be better off just using what's been suggested and written by the steel industry for decades. They spent a lot of time and money using some pretty smart engineers to come up with all that metallurgy stuff. The main problem seems to be finding the proper quenchants in small quantities.
It's still fun to play around with different methods and quenching goops and old found pieces of farm steel as long as we realize it won't make the best blade we could using modern methods and materials. I guess it's a lot different for a hobby guy like me goofing around in his garage making a few knives for friends and family and a pro depending of repeat business for quality blades.
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You are correct - using unknown materials and un-proven methods might be fun, but they are always far more expensive and time consuming in the long run.
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THANKS for all your time and expertise, guys!
Dan
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Karl, I'v been away for a couple of days.
You have layed it all out pretty well to me. This subject is the most fascinating part of knifemaking to me.
From what you have said, I am even more convinced that I had heated the oil too much. Just a little. The two blades in question did harden, but not to that crisp, file skating hardness.
Back to oils, I have been using 5160 and 1084 quenching in the same oil. This has been successful for me, except for the above mentioned blades. The small variance in hardness, is probably a temperature related thing involving, perhaps, two different batches of 5160. I say this because the two that are giving me the problem are from a different size bar stock. I heat treated three from that stock. One did acceptable, the other two not. The only difference being that I probably had not heated the oil so much on the good blade.
My oil has always been successful for me till the above temperature thing. I am using a water soluable oil, believe it or not. I use very little water in it, maybe a quart to a gallon and a half. I had not had any experience with such an oil and will probably phase it out, but I have used it with success and dont want to get rid of it yet. It's has low flash point and does'nt seem to have a vapor jacket problem.
I have some Texaco Super quench that I want to use soon and see how that works too. Someone gave that to me so I'm not sure if Texaco A and Super Quench is the same oil or not. I will get me some in either case, because it's time for it.
This stuff is not magic and it should be as predictable as we can make it. The information shared here really helps. I hope that all reading will stick to the main stream, but not be too afraid to experiment for themselves.
Good stuff. Lin
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After 20+ years of using mineral and veg oils, (I think successfully), I'm going to bite the bullet and get some real HT oil. We do owe it to ourselves and our customers to narrow down all the variables we can.
Thanks guys for all the info!
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That's the great thing about 1084! Get it hot and quench it in something wet!
Not really, but almost.
You can heat up some "slow" oil or keep some "fast" oil room temp.
1084 will harden!
But, above all, keep this stuff simple, everybody. Once you get your "stuff" figured out, where you are "shop-wise", then improve things one item at a time.
Your fun and pleasure will improve as well!
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man this is good stuff. loyd
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I’m a new maker trying to learn. I have quenched a couple of 1095 blades in water and they seem to have hardened well. They where defiantly brittle as I broke one of them in two with my bare hands! Is water acceptable for 1095? If not what should I get? What in your opinion is the best/easiest to HT steel for a maker with only a coal forge and oven for heat treating? 1084? What about 1095?
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Bryant,
In my opinion, the simple steels are the easiest to quench successfully. Even these can have variations in alloy consistancy and will affect hardenability, but not by much. 1084 is a good one. I would use oil, not water, but water will certainly harden it. That includes 1095. The problem is, water will often stress it so much that it cracks or breaks.
Go back through this thread and also read some of the other threads about heat treating various steels with various oils and get a better idea of what you need to do. All of the steels you mentioned are great steels. Lin
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Hey Bryant,
I grew up in Thomasville and my brother works at the Weyerhaeuser mill (old McMillan Blodel mill) up near you.
If the blade broke before you tempered it in the oven, then that's pretty normal for a dead hard blade. I've heard of them breaking just sitting on the bench after hardening because somebody waited a few hours before putting them in the oven for a temper cycle.
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Thanks guys
I think that after I use up my 1095 I might try to find some 1084. I have some D2 but plan on sending it to Mr. Paul Bos for HT. One day I would like to get a knife oven but just cant justifiy it yet. What supplier do yall get your quenchant from?
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I'm having trouble getting it in 5 gallon quantities. I'm looking too. You may have to try veggie oil. Transmission fluid works too, but smells pretty bad. Lin
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I've been using veggie oil (corn) to harden 1095 for a few years now. For small blades (<5" and under 3/16" thick) it works fine, just make sure to heat the oil beforehand. Try it with a larger knife where there's more heat to extract and you will run into problems.
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You guys are awesome. Such an amazing knowledge of the art and willing to share with those of us who are just tinkering for fun. :clapper: :clapper: :clapper:
What would be the prefered oil of choice if I were to be using o1 tool steel less than 1/8" thick no larger a blade than say 4 to 5"?
Thanks for your knowledge guys. I've been using old saw blades and such and have decided it's time to try and put some consistency in my work. As I think Karl mentioned I owe it to the people who end up with my knives to be as consistent as possible. I was planning on buying o1 since it's easliy available from jantz but 1084 is sounding somewhat "foolproof" maybe I'll look for that instead. Thanks again guys. SKippy
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Skippy, O1 is readily available, but one of the characteristics of it are that to get the MOST out of it, it needs to be held in the 1500 degree range for longer "soak" times than the simpler steels, like 1084.
"Simpler" means that they do NOT have the additional alloying ingredients like O1 that make for the longer soak times.
Some people even hold it in that range for as long as 20-30 minutes!
This, of course, requires heat treating ovens or similar equipment with some type of refined temperature control.
1095 works great with the proper quenchant, without the long, extended soak times.
Look around for some 1084 - you'll find it!
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Karl, THanks for the input. I will definitely look for some 1084. Skippy
Keep up the great work your knives are an inspiration to all of us "wanna be's"
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Send an e-mail to [email protected] for a price list for 5 gallons of Parks 50 or Parks AAA quench oil. Send your address or zip code so he can calculate shipping costs. He makes an order early each month and ships it out when he gets it in.