PDA

View Full Version : My semi-real time heat treating thread



Kevin R. Cashen
05-03-2010, 10:50 AM
Folks probably know that there is nothing that I take more seriously than my heat treating. Because of this “heat treating” day at Matherton Forge is always an all day affair that gets my total and undivided attention. I could slot some guards or shape some handles while the blades are being borne but that would interfere with my continuous monitoring of the temperatures and process, so heat treating day is also a lot of tedious watching and waiting. At first I thought a thread like this would just be a matter of sharing my boredom with all of you, but then what on earth could be boring about heat treating?

Well the Blade show is drawing near and today is heat treating day, and because it is also “empty the tubes, repair leaks and renew the salts” day it will be a particularly long one. So since the computer in the lab is right there next to the testing equipment and a few steps from the heat treating area I thought I would share some of the day with you.

I started the day by turning on the kilns which hold the low temp Thermoquench salts and letting them get a head start in coming up and leveling off at 420F. Next I finished cleaning out the four foot high temp tube I emptied yesterday. By the way here is an tip on that that I found very effective- if you need to empty a high temp salt tube, don’t even think about doing it at temp when they are liquid, take them outside when they are cold and put a garden hose in the top and let it run. This method quickly dissolves and empties the tube in just a couple hours. Warning- only do this with simple NaCl based salts like Parks Nusal, salts with other hazardous elements like barium should not be removed in this way for the obvious reasons.

I knew I had to clean out the bottom of my tube because the last swords had a bit of decarb at the tip which I had to remove, indicating that a contaminant sludge ahs accumulated in the bottom, and sure enough I found a thick deposit and removed it. This is why I now keep my tubes completely covered when not in use to keep dust and debris from getting inside. I have refilled the tube and it is not coming up to temp to melt the salts, it will be a longer process than usual to get it all melted with the tube topped of and running well.

Kevin R. Cashen
05-03-2010, 10:50 AM
My high temp unit is working quite well today, it has been a many years process to develop it to this point but one of the best things I did was to switch over to T-Rex venturi style burners in place of the old forced air burners. Forced air is what I prefer for forges but the salt bath firing chamber works much better with venturi, provided it burns hot enough to do the job. Ignition is as simple as it can get since I machined socket sleeves to accept the burners and I just light them like a torch and insert them.

I had to meet the mailman out front about an hour ago to accept a package from a good friend who I am helping out with some sword heat treating; the timing seems miraculous but I planned this day according to when the package would arrive. I also have a batch of blades to do myself. The day goes the quickest if I have all the same steels and all the same blade styles since all the temps and times will match. But when there are different austenitizing temps and different tempering temperatures, it takes longer for the units to level off at the next temperature. Often I will do favors for friends and end up with blades that really need to be quenched in oil so seldom are these days short or quick.

Kevin R. Cashen
05-03-2010, 10:53 AM
I am now heating a test bar of Damascus to quench and then etch to be certain that the new salts are all in neutrality and leaving the carbon in the steel where it belongs and not pitting in any way. I finished it out to 600X and will shine it up when it comes from the low temp. A quick dip in the Ferric Chloride should tell me that things are just fine.

Things actually leveled off rather quickly this morning after refilling the tube, but the sword tube has so much thermal mass that it normally heats up even quicker than my 2 foot tall unit. It is purring along at 1500F now and the test bar should be ready to quench in a couple of minutes.

The low temp have leveled off at 420F. I normally set them there for the initial heating and some quenching so that the greater thermal mass will allow for a more stable setting when I drop back to 400F or a hair lower for tempering.

I have drum switches on some of my thermal couples so that I can cross check the probes and their controllers in order to be certain all are running within 2 degrees of my set temperatures. Both high and low temp are reading fine.

I let that test bar soak for an extra long time since I am checking the salts and want to be certain of their integrity. I will go quench it into the low temp salts now and after things level off for a couple of minutes I will air cool it, rinse it, polish and etch.

Gabe Newell
05-03-2010, 11:29 AM
Couple of questions since you are passing the time:

1) What steels do you always/never/maybe quench in your low temperature pot?

2) Is cross contamination between the high temperature and low temperature pots not an issue?

Kevin R. Cashen
05-03-2010, 11:40 AM
Perfect! The bar etched beautifully and gave me continual 64.5 HRC readings. This is what I have always loved about my Damascus mix by the way, I could use it for a calibration block if I wanted. Unless there is something really wrong this mix always consistently gives 64.5 HRC without fail. It is actually much more consistent than any single carbon steel I have tested. So much for all the old wives tales about not being able to Rockwell any type of damascus.

Well the first blade has gone into the salts. This first one is another job for another maker, which I really am not in the business of doing but this maker got a request to specifically use my damascus in this knife, from a customer who was adamant that it was the best available. Well, I found this so flattering that I reminded them that the steel is only as good as its heat treatment and that I would be happy to run it through with my blades to insure the customer got the most from this steel.

I took just a couple of minutes for rebound and I have now set the timer. You see when the blade goes into the salts it lowers the overall temperature. A blade this size drops the temp from 1500F to 1492F and then takes a couple of minutes to rebound. As soon as the temp reads 1500F again I hit the stopwatch I am wearing around my neck and wait for 4 to 5 minutes to elapse.

All Done! The blade went into the 420F salts and was allowed to assume that temperature before removal fro air cooling. It is cooling now. It is a good blade but there is always those little areas for improvement, this one had the tip just a little off center to my eye and I was looking forward to tweaking that. At 420F that was not problem I just put my gloved thumb on the end and pushed it into perfect alignment. I always agonize over the possibility of warping somebody else’s blade in heat treating and it is one of the reason I don’t often volunteer to do it, but it is a real treat when you can actually send it back even straighter than you got it.:cool::D

Gabe Newell
05-03-2010, 11:45 AM
... and which hardness tester are you using?

Kevin R. Cashen
05-03-2010, 11:49 AM
Couple of questions since you are passing the time:

1) What steels do you always/never/maybe quench in your low temperature pot?

2) Is cross contamination between the high temperature and low temperature pots not an issue?

Thanks for chiming in Gabe, a little chatting is what I was hoping for to pass the time.

1. any steel designated as oil hardening works in the low temp salt- O1, L6, 5160, 8670m, 52100 etc... Steels such as 10XX series, W2, 15n20 get Parks #50 here instead.

2. From low to high is a problem, an immediate problem:eek: From high to low just happens but the high temp salts solidify and flake off to sink to the bottom of the tube. Eventually I will need to empty this tube and clean out the debris as well, but it will take a while yet. Emptying the low temp is more difficult because it does not dissolve as readily in water.

Kevin R. Cashen
05-03-2010, 11:58 AM
... and which hardness tester are you using?

The Chinese made benchtop model that I tuned up myself to insure it reads on. It has actually has done pretty well over the years. But I spare no effort on the quality test blocks to insure it does read well.

Kevin R. Cashen
05-03-2010, 12:30 PM
O.K. I am into some of my own bowie blades now. They have a greater mass so the rebound goes down to around 1478F and back up. My neighbor has a pole barn with white siding that is really great to sight down the blade on when I have my slider doors open on these warm spring days. I stand at my anvil with a wooden block on top to protect the finish and just guide the blade on it, or in my gloved hands, as it hardens from 400F to room temp. Fro swords I go into the finishing shop to put the tang in a vise and sight down my light colored counter tops. But there I can hit it with intense light and have both hands free to work things.

As I age my eyes really have a harder time focusing down the length of long blades to do this work, but as long as the cataract in my left eye stays as small as it has for the last several years I should be good for a while yet.

When the low temp salts go completely solid you are into the M80% range and it is best to leave the blade alone. Before I temper I will dip all room temp blades in cold water to be certain I have surpassed M90%. If one is not martempering this may not be a good idea though and could result in cracked blades before the temper.

Darrin Sanders
05-03-2010, 01:21 PM
I noticed that you mentioned 8670M above. I have been thinking about trying some since I can't find L6 barstock. What is your opinion on it in relation to L6? I would be using a digital oven & 11 sec. oil for H/T.

Kevin R. Cashen
05-03-2010, 02:47 PM
Darrin, I think 8670M it is a pretty good steel as long as you know what it is and that it is not L6. I have heat treated a bit of it and have found it to be pretty consistent, even moreso than 5160 for instance. It should be tough, not as tough as L6 but it will also be easier to work with than L6. If a person has had good luck with 5160 they should do real fine with 8670M. It should harden real well in just about any oil.

Kevin R. Cashen
05-03-2010, 02:54 PM
The hardening part is now done for all knives and now I get to play the greatest waiting game of the tempering cycles. All the knives have been hardened, Rockwell tested and are now between the first two tempering cycles. The first cycle was at 375F for around 40 minutes just to stabilize things. Times in salts can also be much shorter than ovens, but once I find the hardness level I want I will give it a good long and full temper. Now I will go to 390F for a longer temper for any hunters and keen slicing blades. The temperatures will increase slightly for the bowies and even more for the sword.

Kevin R. Cashen
05-03-2010, 03:23 PM
Don't worry; I won't go all safety Nazi on you folks but something occurred again today that is probably worth mentioning. About 2 year ago my good friend Ric Furrer told me to get a CO detector and put it in my shop, something that very few of us do despite the number of us with massive gas combusting equipment. My salt baths are with my forges in a separate room from my finishing area, and in that forging area I have two barn sliders and a regular door along with a vent fan at ceiling level. My CO detector is above my bench in the finishing area with just a normal doorway connecting the two rooms. Since my vent pipe rusted through I ran without it today with all the doors open, but it still set off my CO detector in the other room. I turned on the vent fan and took care of the issue, but it is worth mentioning that my salt baths give off much less exhaust than the typical gas forge.

This is something to consider whenever we fire up a forge in an enclosed area. I myself am pretty glad my friend pressed me to get that detector. Otherwise I would still be breathing that garbage like I did for too many years previously.

James Terrio
05-03-2010, 03:49 PM
I got even less than usual done today, because I kept sneaking in to check this thread. Thanks Kevin, it's been fun!

Kevin R. Cashen
05-03-2010, 03:55 PM
All of us suffer with trying to get as much as we would like accomplished in our shops everyday, I am glad I coud help out:D

James Terrio
05-03-2010, 05:25 PM
I think of it as research, so in that way it's productive! :)

Seriously, this has been really interesting to me, even though I don't do my own HT. Once again, you've added a lot to my very-slowly-evolving understanding of the procedures, and I thank you for that. Coffee or beer is on me if you ever happen to be in my lil town ;)

Troop
05-04-2010, 05:42 AM
Kevin, I know this is an understatement, but, a sincere "thanks for posting".
Not trying to be a suck-up, but, I've learned a great amount from you.
- thanks again.

McClellan Made Blades
05-05-2010, 01:07 AM
The Chinese made benchtop model that I tuned up myself to insure it reads on. It has actually has done pretty well over the years. But I spare no effort on the quality test blocks to insure it does read well.

Kevin,
Being the frugal miser that I am, OK, poor guy with no cash to speak of, I end up buying Chinese (crap) quite often, surprisingly it does do fairly well, although it irks me to no end that the money I spent could have employed a hard working American. I'm not familiar with a China made Rockwell tester, mind sharing the particulars about where to find one, the cost and the the quality test blocks you use as well? After reading the "Quench Wars", I'm getting a tester, just to be on the safe side, and KNOW-not ASSUME what the hardness is of my steel.
BTW- I want to thank you for the time and effort you put into sharing your knowledge, I know it's not something you have to do, the information you provide has been priceless. Especially when I can comprehend what your saying! When you have time, could you post the sequence for Hting the basic steels like 1095, 1084, etc. I know those 2 are similar but all the info out there has different ways of doing it, one says to soak 1095, while others says not to, I guess what I'm saying is dumb it down for folks like me, a step by step procedure would be awesome. I'm sure there are plenty of guys out there (if they would admit it) that would appreciate you doing that. I'm not asking you to do every steel available, just the 10XX series, mater of fact 1095 and 1084 would be more than enough, as they are the most widely used forging steels, that's an assumption, based on the fact that that's what I use.
1084 would good enough for me, because of your explanation of Eutectoid steels I chose 1084 to be my primary steel, which I have to thank you for, it has made my learning curve so much easier. I have my HTing down pretty good for 1084, but after the quench wars, I will be finding somewhere to have mine Rockwell tested until I get my own tester, I used Canola oil for the first few months when I started and finally moved up to a real quench oil, which is the McMaster Carr 11 second quench. I would greatly appreciate your view on this quench oil, since I just bought another 2 gallons, right before I read Quench Wars! I think may have put up with the crazy company that makes the Parks quench oil. But the results on that test were weird.
It's late and I'm rambling, I would love any information, opinions or views that you can share, Thanks Rex

Kevin R. Cashen
05-05-2010, 08:12 AM
Rex, I typed you out a large full page, descriptive reply and then lost it all when I hit the wrong button:mad:

I will see what I can do for you, but right now I am too disgusted and have ran out of time.

McClellan Made Blades
05-05-2010, 09:36 AM
Rex, I typed you out a large full page, descriptive reply and then lost it all when I hit the wrong button:mad:

I will see what I can do for you, but right now I am too disgusted and have ran out of time.

Kevin,
I know all too well how that feels, it's a sickening feeling. And that's perfectly fine, I understand totally, I also know it's probably the worsed time of the year for such a request. So, when ever you can get to it is fine, it doesn't have to be in your usual detail either, a simple list of how you do it is fine. From your past writings I understand more about HTing than I ever would have. Just a list like: For 1084-
First: heat to XXXX, the temp you start at, and the temp you stop at to quench. How long to soak if there is one, and how you quench. I like a differential HT, for my larger blades, and usually try to get a hamon. My success rate on hamons has been best doing an edge quench. Although, I still do a clay coat sometimes, with 1084 getting a hamon with an egde quench is almost a guarantee. With clay, I haven't dialed that in yet.

I prmarily use Aldo's 1084, but I have some other steels that I use from time to time, I got from Aldo also, I know he's known for his 1084(fg) but he has some fine 1095 as well, and I think the steels he's going to have available for knife makers is going to be awesome. He's busting his butt trying to get W-2 in bar stock. I got some W-2 from him in 1/2 inch bar stock that I like really well, I didn't get that sick hamon on it, but it still made a fine blade.

Looking forward to hearing back from you, at your leisure. I know with Blade coming up, your busy. So it's no rush. I appreciate you taking the time to let me know that you had it written up, even if the puter monster ate it!
Thanks again Bud, Rex

HELLGAP
05-05-2010, 10:36 PM
Kevin wow alot of typing and alot of reading . I read most but not all the poste on this thread so far. I got to the part about L6 and figured I need to ask . I aquired 3 saw blades made from L6 big 36 /40 inch diameter comercial blades. everyone told me L6 and my brother in law asked they said L6 so to make sure I could send off a piece to make sure and it would be worth knowing for sure. If In fact this is L6 will this make nice straight razors. The saw blades are near a 1/4 thick , will it be ok . Or should I just buy some 1084 1/4 thick . kellyw

Kevin R. Cashen
05-09-2010, 09:06 AM
Kevin,
Being the frugal miser that I am, OK, poor guy with no cash to speak of, I end up buying Chinese (crap) quite often, surprisingly it does do fairly well, although it irks me to no end that the money I spent could have employed a hard working American. I'm not familiar with a China made Rockwell tester, mind sharing the particulars about where to find one, the cost and the the quality test blocks you use as well? After reading the "Quench Wars", I'm getting a tester, just to be on the safe side, and KNOW-not ASSUME what the hardness is of my steel.


While I applaud anybody’s efforts in pursuing truly accurate and effective means of testing, the Rockwell tester needs to be viewed in the same way as any test in a field where so many have an undying and oversimplified belief in single tell-all tests. There are no single tell-all tests, and the closer you get to general tell all type tests the less accurate and reliable they become. The most accurate tests measure one single aspect very precisely, but cannot provide an overall big picture and only through the combining of many little pictures can you get an accurate view of the whole.

First off, it cannot be repeated enough in order to help folks out with a widespread confusion about hardness testing, that there are different forms of what we call “hardness”; here I will focus on the two we most commonly encounter. The most common that knifemakers look for is “scratch, wear or abrasion hardness”, this is what we check with files (think of the very old Mohs Scale measuring one mineral scratching another). For this discussion I usually use the analogy of imagining a ball of Playdoh loaded with glass shards. If you pass a file over the surface of your doh ball it will skate off the glass and register things as VERY hard.

The next hardness we will consider is “penetrative hardness”, it more accurately describes the materials strength in not being pushed aside as an object is forced into it. For this visualize our same Playdoh ball, but take the handle off the file and shove the tang straight down into it. Of course the tang will simply push the glass aside and sink into the ball as if it were nothing but Playdoh.

Now we have two tests of “hardness” but one is saying the material is as hard as glass while the other is saying it is as soft as Playdoh?:confused: Which one is correct? Well, they both are but only as long as we are well aware of what it is we are measuring, and combining both tests will give us a more complete picture all around.

Bladesmiths have come to rely on a few tests believed to be “tell all” with no real concept of what it is that those tests can measure, leading to way too much confusion. And in the meantime they have turned their backs on tests that can very accurately measure specific things because those tests did not tell them what they wanted to hear. One of the greatest examples of this is the almost hackneyed “brass rod” test which relies on flexing the edge. Flexing anything made of steel is almost solely a function of the cross section and the only time the heat treatment (hardness or softness) comes into play is when the yield point is exceeded, i.e.- “snap” or bend. Since this “test” can only measure the mode of failure it really tells us next to nothing about scratch or penetrative hardness yet is believed by many to be a reasonable replacement for Rockwell, one of the most accurate measurements of a true hardness.

I only bring all of this up as a reminder that to rely on one test without realizing its limitations is no better than no test at all, and worse if it leads you in the wrong direction.

Files are a good quick way to check scratch hardness as long as you know everything else is in order, but a file cannot detect fine pearlite (the soft stuff made when the quench didn’t quite do its job) any more than it could detect Playdoh between piece of glass, I have very detailed proof of this for any doubters. On the other hand the powerful Rockwell test can also only tell you about one specific thing- the overall strength of the material as measured by penetrative hardness, it will indeed very quickly tell you if you have any fine pearlite as it pushes the hardened bits aside. But the Rockwell test can tell you nothing about the grain size, carbide size, and many other important features inside the steel, in fact in the case of grain growth the Rockwell readings will be even higher!

So, look into a Rockwell tester if you want more precise readings of penetrative hardness (and trust me you do want that), but also realize that that is all it will tell you about and is best used in combination with other tests for the total picture.

The unit I use is a common hardness tester that you can get right now at Production tool Supply for $999.95 (# NR50-900330), although I think I may have gotten mine from Enco. It is not an expensive brand name model but using a tester is like sighting in a rifle, if it will give you a nice tight grouping all you need to do is adjust your windage and elevation, if you know what I mean. The sighting in of these units is all in the test blocks, so even if you have a cheaper unit, if it reads consistently and is adjustable the test blocks is where it is as and the tester can only read as true as the blocks, so one can get better results with a cheap tester but excellent test blocks than a guy with a top of the line tester but cheap test blocks.

Good test blocks will start at around $75 and should be NIST certified to insure accuracy. Look for ones rated in the range you plan to work in the most, so 57-63 HRC would be good.

Always remember that these testers are designed to be very accurate and, like any precision instrument with that level of accuracy, can be easily affected if you are not careful with their use. I keep mine in a heated lab area in my shop because the hydraulics are effected by cold and will skew the readings, also continuous heating and cooling will create internal condensation and corrosion which is bad for any instrument. Use an old piece of clean steel to take several “disposable” readings off from at the start of a testing day to compress all the parts and squeeze the oils on the elevator, after this warm up the tester should be in working order. I use my expensive test blocks to calibrate the tester every so often but make up my own everyday test blocks to double check things (I am anal retentive to the point of neurosis in their creation however).

Test pieces need to be over 200X finish for truly accurate reading (I like 400X). Readings not taken on a flat level surface will not be trustworthy as the micro-crater created by the penetrator must be symmetrical on all sides, one side giving way will result in a false reading. The anvil and the test piece MUST be clean. If I ever hear that almost inaudible “crunch” sound of dust being squeezed under the major or minor loads I discard the reading and do it again after cleaning things off thoroughly.

One single reading is not worth much. I prefer at least 5 readings over an area with the resulting number being an average of these, any readings more than 1.5 HRC deviation from the rest should be redone to confirm.

As you can see I am really a geek and take all of my testing very seriously and insist on verifying all data, especially my own.

I will post answers to your other questions, but right now I am being summoned away from the computer with subtle reminders that it is Mothers day;) .

Gabe Newell
05-09-2010, 11:32 AM
Having already provided fire support for my children's spectactularly enthusiastic Mother's Day activities, I can relax and read through this thread again.

Kevin, your formal testing seems to entail Rockwell hardness, etched micrographs, and impact testing. Does that cover it, and do you ever send samples out for chemical analysis, SEM or x-ray testing, microhardness etc...?

Kevin R. Cashen
05-09-2010, 03:24 PM
Micro-hardness can come in handy, and through connections I have had that test available but not close by until recently, but now I have easier access should I require it. Due to my insistence on using steel with chemistry sheets provided I have not had much call for that, the chemistry is the chemistry and unless you really screw up you don't change it much in making a knife. However, now that I am making a bit more of my own steel I am feeling the need for chemistry checks a bit more, so I often look around for that equipment and daydream about having the funds. X-ray diffraction can be handy in looking for retained austenite, but if you do things right it is not enough of and issue to lose sleep over, and there are other ways of troubleshooting it if you know what to look for.

My other tests consist of various edge tests and microscopic examination of the same. I am currently planning a micro-impact test designed specifically for edges. For the most part I also use the heck out of test blades in ways that at least resemble what you would do with a knife. One the most puzzling things I have always noticed about knifemakers are the number of tests they use to show the quality of their knives that have absolutely nothing to do with what knives are meant to do.:confused:

Edited to add- I would like to be clear about my sincere belief that most of these things are NOT necessary to make a good knife, microscopes and other analysis equipment are handy if you want to get deep inside the steel but are ridiculous overkill just to make knives. Simply following sound heat treating principles and good shop practice can insure that I make quality knives, but the real reason I built a special room to fill with the metallurgical gadgets was to insure the quality of the information I provided to counter the loads of entrenched hooey in the knifemaking community. I believe people should have more than the assumptions and "say so" of well known makers or hype designed to sell magazines when being offered information about what we are doing. My "lab" work is for my quirky and expensive metallurgical nerd hobby, much more than for making knives.

BossDog
05-09-2010, 04:34 PM
Kevin, any update on the heat treat book you were working?

James Terrio
05-09-2010, 05:36 PM
I happily confess to using the brass-rod test on my knives, both ones I've made and ones I've bought. I fully agree that the results very often have more to do with edge geometry, than they do with the steel itself, although material properties and subsequent treatment certainly are a factor.

The results of such a test are extremely unlikely to fully describe the properties of the steel, or the way it was heat-treated. But they may very well give some insight to the knife's actual performance.

I'm aware that brass-rod test results don't mean doodly-squat as regards the Rockwell-C hardness of the blade, or what the true chemistry of the steel is, or whether the blade will tolerate being bashed through a tree. Nor do rope-cutting tests, banging the spine against an anvil, or burying it in wet soil to see how quickly it corrodes.

Having said all that, I humbly submit that for most "user" knives (camp, combat or kitchen, envelope-opening or crate-opening, slicing steak or 'deanimating' bad guys :rolleyes:) the brass-rod test is a fairly decent indicator of whether or not a given knife's edge will roll over or chip out during its intended use.

I'm NOT saying the brass-rod test, or cutting rope, or slicing meat for that matter, is the only, or best, way to determine a blade's overall quality! I'm very glad that bladesmiths like Mr. Cashen and their counterparts in industry have put so much time and effort into testing steels, HT procedures, etc. Their research is incredibly valuable to anyone who enjoys good cutlery of any sort.

But frankly, I feel the only way to find out if a given blade will withstand the work it's designed for, is to use it that way and see what happens.

That's just my experience, based on use and intentional abuse of several knives made of several different steels. On a certain level, I don't give a hoot what the Rc number is, if my knife stays sharp and doesn't break while I'm using it. Does this seem reasonable?

Thank you Kevin, and KnifeDogs.com, for letting me ramble :)

Kevin R. Cashen
05-09-2010, 06:18 PM
…BTW- I want to thank you for the time and effort you put into sharing your knowledge, I know it's not something you have to do, the information you provide has been priceless. Especially when I can comprehend what your saying! …


Kevin, I know this is an understatement, but, a sincere "thanks for posting".
Not trying to be a suck-up, but, I've learned a great amount from you.
- thanks again.


I think of it as research, so in that way it's productive! :)

Seriously, this has been really interesting to me, even though I don't do my own HT. Once again, you've added a lot to my very-slowly-evolving understanding of the procedures, and I thank you for that. Coffee or beer is on me if you ever happen to be in my lil town ;)

Gentlemen, let me just say that you are most certainly welcome. The opportunities I have been given to hands on teach this craft is the second most rewarding thing I have experienced after actually making blades. Other than idle conversation most folks have an agenda when expending time and effort in venues like this. For many the motive of advertising is more obvious than others, and I am saying nothing negative about that, this can be a great way to sell yourself or your products as long as you are honest about it. But for me it is about the information and with that I too have an agenda, and if it has not been plain to see allow me to state it definitively- my agenda is to provide enough sound information about how steel really works that one day all the hype and myths that have been stifling the growth of our craft for too long will fade away. I have said enough times before to have been quoted that “I hand out information like free guns to an oppressed population”, and for much the same reason.

I don’t believe I could ever tire of typing detailed two page posts to help with the questions of people sincerely looking to improve their knifemaking success, but my single greatest regret are the potential friends I have lost in my efforts to bring solid information to our craft. The way my mind works, it cannot fathom why verifiable facts could put you at odds with other people, but much to my chagrin many react to such input much the same as an established aristocracy would react to free guns in the hands of the peasants. In all sincerity, not a day goes by that I do not agonize over the hard feelings created by my efforts to dispel bad information, but if the price of those friendships is for me to compromise my principles by ignoring facts in order pander to myths and marketing, then the price of that solace it too high for me to pay.

So if my goals and ethics force me to accept the hostility of some of my peers, let me express how the kind words of support and gratitude from gentlemen such as yourselves truly give me the strength to hit “enter” some days after typing a post that I know will only increase the level of grief from people I will always wished could have been friends.

My sincerest thanks back at you gentlemen.

Now if you can only give me some relief from the grief I get from my wife about how all this free information should be saved for my book.;)

Kevin R. Cashen
05-09-2010, 06:32 PM
...
But frankly, I feel the only way to find out if a given blade will withstand the work it's designed for, is to use it that way and see what happens...


This is exactly my position as well, all the fancy lab test I do are for studying the materials and the processes but the only thing that will tell you how good a knife is is to use it as a knife. This is my issue with so many "tests" that will look impressive on a full page ad or draw a crowd at a major show, but have nothing to do with using a knife. Just use the knife. Use it hard, but in just the way it was meant for. I personally like clearing fence rows with large blades, half a day of hacking and chopping who knows what, will tell you how the blade hold up, how the handle treats your hand, how effective every type of strike can be. There is no more brutal environment for a knife than a kitchen! Short of hacking rocks nothing in the outdoors will challenge a knife edge like heavy food preparation, this may sound silly but give it a try and you will realize that if a knife can handle a week in a real busy kitchen, it it more than a match for anything Rambo could throw at it. Cutting rope is fun, I guess, but if you know somebody who processes deer during season in a state like MI;) drop off some knives for them to try and listen to what they tell you when you pick them back up.

Any of these things would be worth ten times more than Rockwell testers, brass rods or spectrographs in determining a good knife.

Edited to add: I just thought of a recent example of how much more complicated edge strengths can be than the brass rod test would indicate. Just 4 nights ago I tested an edge to destruction that handled flexing over a rod with no problem, it was hard to even get it to flex but no chipping or rolling could be induced in gradual flexing. I then commenced to hacking a 3/4" brass rod at various angles of attack to the edge with increasing force until I got any failure I could. At the point of taking 1/4 deep bites from the metal I finally got both deformation and chipping in the same edge impacted with intentionally off kilter blows. I have to wonder which mode of failure the rod flex would have shown if able to be pushed to the yield point? In the end it won't haunt me too much because I find the impact testing more closely resembles the forces that large bowie would have seen. With both brittle and ductile failure occuring in the same edge one can get how looking at many aspects would be the only way to understand the entire picture.

Kevin R. Cashen
05-09-2010, 06:42 PM
Kevin, any update on the heat treat book you were working?

Speaking of that book that so pits my wife against me:D Life continues to get in the way. I was ordered by my better half to stop working this winter and sit down to finish that dang book! Then I got called to teach more this winter than in any previous year- teaching pays bills, writing and rewriting chapters all day does not:(. I will continue to pursue its completion since it remains the biggest unanswered challenge of my entire career. There are days when that book makes me feel like the guy who has been engaged to the girl of his dreams for ten years while everybody around him wonders what his problem is:o.

Kevin R. Cashen
05-09-2010, 06:44 PM
When you have time, could you post the sequence for Hting the basic steels like 1095, 1084, etc. I know those 2 are similar but all the info out there has different ways of doing it, one says to soak 1095, while others says not to, I guess what I'm saying is dumb it down for folks like me, a step by step procedure would be awesome...

I will try to give you as much information as I can but I will avoid providing a “recipe”. There is a profound irony in the number of homespun bladesmiths that will advise that you do things just like they read in a magazine or were told by their grandpappy because they know it works without having to know why, but then accuse those who follow spec sheets or the “Heat Treaters Guide” of merely being “recipe readers” . A person only concerned with making Grandmas biscuits exactly like she did works with recipes, a top chef is capable of making anything without recipes because he is armed with a knowledge of what each ingredient and cooking process will do. I prefer to give people tools in the form information to write their own recipes.

1084 and 1095 are the two ideal steels to start such a basic discussion with. They are both of the simplest carbon steel 10XX series, representing the simplest of all (eutectoid- at .84%) and the extra considerations involved with the addition of extra carbon in 1095. When considering Crucibles Cru Forge V, more than once I have thought the concept of developing a steel just for bladesmiths was redundant when you consider that we have had 1084 for all these years. A simple steel with no extra carbon or alloying to worry about in forging or heat treating with minimal equipment, and an extra pinch of Mn to help quench things more effectively, and yet still shallow hardening enough to facilitate the differential hardening so many smiths have such a penchant for. While capable of versatility in the hands of veteran knifemakers 1084 really is the perfect bladesmithing steel for beginners.

Heat 1084 anywhere in a range from 1475F to 1500F with no real soak time and quench it in any reasonably quick oil and you should be able to produce a knife that will meet your performance expectations. To anneal it all you have to do is get it hot and slow cool it and cut, file or sand to your hearts content. It really doesn’t get much simple that this. This is because of an almost magical equilibrium point for carbon in iron, right around .8%, known as the eutectoid. At room temperature you will make all the same structure throughout with no leftover iron to fill and no left over carbon to get into mischief in your blade. On heating .8% will go into total solution at the lowest possible temperature once again with no left over iron to fill and not extra carbon to deal with. Because of this you are looking good at 1475F and there is no need to sweat if you get nearer to 1500F.

All steels will benefit to some sort of equalizing soak time at temperature so if you can hold at 1475F for a while, great! If you really are more comfortable limiting you time at heat go a little higher and quench immediately.

I am not sure if you are aware of my steel spec. pages on my web site but here is a link with much of the information you may be looking for : http://www.cashenblades.com/info/steel/1084.html

1095 is a different story. 1095 is just one steel that has gotten an undeserved bad rap by true recipe followers using the wrong treatments on it. There are no bad steels only wrong applications and heat treatments. If you fail to recognize that 1095 is NOT 1084 and heat treat it like it is, you will be disappointed.

1095 will have around .15% carbon above that happy eutectoid level to deal with. If this extra carbon is not forced by you to do something useful for your knife, it will find things to do on its own which you will not like. Heating too high will unleash this carbon to run rampant, cooling too slow from total solution will allow this extra carbon to settle into places that will give you grief. So the rules to remember are to keep the soak heat closer to 1475F and forget about the old heat to critical and slow cool methods of annealing that may work fine for 1084. Air cooling is as slow as you want to go, and the best way to soften this stuff while keeping things pretty for the final blade is to cool quick and then reheat to dull red to soften. To fully describe this would entail an entire other thread on spheroidal and subcritical annealing methods but suffice to say that 1095 needs to be treated differently than 1084.

McClellan Made Blades
05-09-2010, 07:17 PM
I will try to give you as much information as I can but I will avoid providing a “recipe”. There is a profound irony in the number of homespun bladesmiths that will advise that you do things just like they read in a magazine or were told by their grandpappy because they know it works without having to know why, but then accuse those who follow spec sheets or the “Heat Treaters Guide” of merely being “recipe readers” . A person only concerned with making Grandmas biscuits exactly like she did works with recipes, a top chef is capable of making anything without recipes because he is armed with a knowledge of what each ingredient and cooking process will do. I prefer to give people tools in the form information to write their own recipes.

1084 and 1095 are the two ideal steels to start such a basic discussion with. They are both of the simplest carbon steel 10XX series, representing the simplest of all (eutectoid- at .84%) and the extra considerations involved with the addition of extra carbon in 1095. When considering Crucibles Cru Forge V, more than once I have thought the concept of developing a steel just for bladesmiths was redundant when you consider that we have had 1084 for all these years. A simple steel with no extra carbon or alloying to worry about in forging or heat treating with minimal equipment, and an extra pinch of Mn to help quench things more effectively, and yet still shallow hardening enough to facilitate the differential hardening so many smiths have such a penchant for. While capable of versatility in the hands of veteran knifemakers 1084 really is the perfect bladesmithing steel for beginners.

Heat 1084 anywhere in a range from 1475F to 1500F with no real soak time and quench it in any reasonably quick oil and you should be able to produce a knife that will meet your performance expectations. To anneal it all you have to do is get it hot and slow cool it and cut, file or sand to your hearts content. It really doesn’t get much simple that this. This is because of an almost magical equilibrium point for carbon in iron, right around .8%, known as the eutectoid. At room temperature you will make all the same structure throughout with no leftover iron to fill and no left over carbon to get into mischief in your blade. On heating .8% will go into total solution at the lowest possible temperature once again with no left over iron to fill and not extra carbon to deal with. Because of this you are looking good at 1475F and there is no need to sweat if you get nearer to 1500F.

All steels will benefit to some sort of equalizing soak time at temperature so if you can hold at 1475F for a while, great! If you really are more comfortable limiting you time at heat go a little higher and quench immediately.

I am not sure if you are aware of my steel spec. pages on my web site but here is a link with much of the information you may be looking for : http://www.cashenblades.com/info/steel/1084.html

1095 is a different story. 1095 is just one steel that has gotten an undeserved bad rap by true recipe followers using the wrong treatments on it. There are no bad steels only wrong applications and heat treatments. If you fail to recognize that 1095 is NOT 1084 and heat treat it like it is, you will be disappointed.

1095 will have around .15% carbon above that happy eutectoid level to deal with. If this extra carbon is not forced by you to do something useful for your knife, it will find things to do on its own which you will not like. Heating too high will unleash this carbon to run rampant, cooling too slow from total solution will allow this extra carbon to settle into places that will give you grief. So the rules to remember are to keep the soak heat closer to 1475F and forget about the old heat to critical and slow cool methods of annealing that may work fine for 1084. Air cooling is as slow as you want to go, and the best way to soften this stuff while keeping things pretty for the final blade is to cool quick and then reheat to dull red to soften. To fully describe this would entail an entire other thread on spheroidal and subcritical annealing methods but suffice to say that 1095 needs to be treated differently than 1084.



THANKS Kevin!!! That info is perfect! One question, if any amount of soak time will benefit all steels, why not do it? Is the benefit so slight you won't be able to tell the difference? Thanks for the help, and NOW I've got your web site saved in my favorites. Thanks so much, Rex

James Terrio
05-09-2010, 07:30 PM
In the interest of not rambling, I'll simply say "thank you". :)

Kevin R. Cashen
05-09-2010, 08:34 PM
THANKS Kevin!!! That info is perfect! One question, if any amount of soak time will benefit all steels, why not do it? Is the benefit so slight you won't be able to tell the difference? Thanks for the help, and NOW I've got your web site saved in my favorites. Thanks so much, Rex


The benefit to many steels is enormous, the only reason I touch in the subject of not doing it is the number of people who may not be able to do it. It is not all that easy even for me to hold a blade at exact temp for several minutes in a forge. It is a really unpopular message to deliver to bladesmiths, the guys that have been told they can produce the best blades ever, that they don't really have the tools to maximize the potential of the majority of steels today, but it is a fact that the majority of steels today were developed long after the simple forge was obsolete for working steel. Can you see another reason why the simplicity of 1084 is very good for bladesmiths? But if one has a controlled oven, there is no reason not to go for at least a 5 minute soak on almost any steel.

One can watch the HRC values climb with every minute of soak time for most alloy steels, and then one can really see the difference in tempering temperatures required after a proper soak. Steel that has has been heated quickly in a forge with no soak my only need a bit more than 350F to temper to working hardness, but the same steel with a proper soak will invariably need in excess of 400F to go from the 62HRC range to a 59-60HRC. For hunters this is great I can just heat quenched 1084 to 400F and call it good, but for large chopping blades, properly soaked 1084 can take me all night to walk in a proper temper as high as 500F to get below 58-59 HRC.huh1