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David Eye 01-21-2016 09:42 AM

Ht procedure questions
I have been doing much research here and elsewhere to educate myself on heat treating procedures of various high carbon steels for knife blades.
I am not new to technical data in general but I am new to knife making. My background is technical and electro/mech in nature with much experience in many different things in my 60 years of life.
I do NOT have any experience with doing any actual heat treating of high carbon steels although my brother in law and nephew had a large heat treat business for years and I did pick up some BASIC knowledge.

I am not only gathering info but also equipment and am currently building my own electric kiln. I have been known to be a rather "exacting" person and I always strive for excellence no matter what I'm doing/making. Sometimes this can cause me to be somewhat overly concerned regarding details that may not be super important, but none the less this is my nature. I believe in doing things right the first time if at all possible. I realize I will make some mistakes and will learn from them, but I am attempting to keep my mistakes at a minimum and gain some knowledge first from people who already know the answers and methods that work for them regarding heat treating and other knife making techniques. Not everyone's methods and techniques are the same but work for them.....I am keeping this in mind while gathering info.

Against all suggestions found on the type of steel to start out with as a newbie, I will be using CRA 1095 that I already purchased from Admiral Steel. I live in the Midwest and Admiral Steel is nearby which kept the shipping charge lower. I WILL be using 1095 so please do not attempt to steer me towards 1080/1084.....Admiral did not have any CRA 1080anyway and I would prefer 1095 for my own personal reasons. I am confident in my abilities that I will be able to successfully HT 1095 with the proper knowledge and a little practice. Compared to some other things I have accomplished in my long life (deliberately and not deliberately) I feel 1095 heat treating is very doable with the proper equipment and knowledge. I will no doubt perfect my technique in time with practice.

From what knowledge I have already found, here is my plan for 1095 HT. I would greatly appreciate input from 1095 experienced people.

1) Since I am using CRA 1095 I shouldn't have to anneal or normalize, but you tell me.
I will be doing my drilling and major grinding first before HT.
2) Heat Treat in my elect. kiln to 1475f and hold for 5-10 minutes.
3) Quench approx. 7 seconds total, and I realize I have less than 1 second (in the quench) to
have the temp drop to under 900 degrees.
4) Temper. I believe right away after blade is down to 150f or maybe hand holdable.
I will temper @450f for 2 hours, let cool to room temp. and then repeat.
5) Final grind and hand sand carefully to not overheat.

I have some questions regarding the heating up and cooling down procedures:

1) I have read some past discussions on this forum regarding "how" to heat up 1095. There seemed to be a difference of opinion at one time as to whether or not to heat up to 1475f quickly or not! Meaning, put blade in cold elect. kiln or preheated elect. kiln.
I am of the belief that I should put the blade in a cold kiln and just heat it up that way and that there is no worry about grain growth unless the temp. would get to 1525+f. Besides, if I were to put a cold blade into a very hot kiln at "X" temp., how would I know how long it might take for that blade to actually be at 1475f for 5-10 minutes?.....doesn't make sense to me!
What are your current thoughts on this?

2) Should the Tempering oven be preheated or not? Does it really matter?., as long as I'm sure the blade is actually @450f for 2 hours (twice) is what's important in my mind, but you tell me.

3) Is it important "how" to cool the blade down to room temperature between Temper's with 1095? Should it be done slowly and left in oven or taken out? Can 1095 be run under cool water to cool down between Temper's or not?

Yes, I am detail oriented and MAY be overly concerned about certain things.........but I want to do the best things that have worked for experienced people and put my mind at ease. I also don't want to waste a lot of time, effort and money needlessly.

Thanks for reading this very long write up and I apologize for any redundancy to previous threads but I just couldn't find definitive answers to my questions.

samuraistuart 01-22-2016 10:50 AM

Welcome David! As you have probably figured out, the reason why we recommend 1080 series for beginners is because their heat treat set up is usually primitive, and it's hard to soak blades in a paint can forge, which 1095 should receive (soak). 1080 doesn't need soak, so equalize, quench.....easy for beginners.

But you're going to be using a use that 1095 up!

As far as normalizing....this is needed when the steel has been forged, OR, the steel is heavily spheroidized from the factory. 52100 is usually coarse spheroidized, and should get normalized. 1095 is usually fine spheroidized, and as such doesn't need normalizing. This you will know only when you fail to reach max hardness out of quench. I personally normalize and thermal cycle ALL spring steels and 52100, regardless. That way I know exactly how the steel is set up for hardening. For now, I would say that Admiral's 1095 does NOT need it....but I'll let others who have actually used the admiral 1095 fill you in on that.

1095 needs a very fast quench oil. Or Brine. Never straight water. Parks 50, DT48, or even 130f canola (not ideal but it works). As you indicated, it is the quenchants job to bring down the steel to 900 in under a second....that has nothing to do with the time it takes to move the blade from heat to oil. I leave it in for a slow 7 count, take out and straighten in needed, back into oil to cool down to room temp.

Yes, temper as soon as it's room temp or just above. Shouldn't be a delay. If you don't have time to do the full temper cycle until tomorrow, run at least 30 minutes at 300f for a quick stress relief.

I would start my tempers MUCH lower than 450f, then check and see where you are. 400f should bring you down to 60-61. If you want to reduce RC more than that, then jump up.

Bring the kiln up to 1475 and place the blade in the kiln once it's warm. It's not a good idea to put it in cold, then ramp up. Always.....warm kiln up, then insert blade. Once the readout has rebounded to your aust temp, then start soak time. 10 minutes plenty with 1095. Now higher alloy steels like stainless and even A2 tool steel, some recommend a pre heat of a certain temp, and then ramp up to aust temp. For example, some alloys may say insert blade at 1400f, equalize, ramp up to 1750 and hold for 30 minutes, quench. This has to do with the alloying in the steel, the more alloying, the more complex the heat treat. But 1095 is about as simple as it gets. I've heard that putting a blade into a cold kiln and then ramping up is not conducive to a fine grain structure.

I turn on my tempering oven when I turn on my kiln. That way it's at my tempering temp when I'm ready to temper.

Between temper cycles, I actually quench the blade in water, but that has nothing to do with metallurgical benefit, and if there is any I don't know it. I quench so I can grab a hold of it quickly, and start the next cycle. You can air cool or quench it in water....your call.

I think its AWESOME you're detail oriented and ready to dive into this head first! There are lots of good guys who know their stuff here who can help with anything you might need.

David Eye 01-22-2016 01:27 PM

Your response is fantastic with tons of info and greatly appreciated.....thanks a ton.
I was beginning to wonder if anyone at all was going to respond to my lengthy thread with a rather long prelude/explanation!

1) If I understand you correctly, after I preheat my kiln to 1475F I then put the blade in. When the kiln rebounds to 1475F I then soak for approx. 10 minutes.....correct? Are you sure the blade will be up to 1475F in the amount of time it will take my kiln to rebound to the 1475F setting?

2) I was planning on using 130F Canola oil as my quench medium.....time will tell! I was planning on quenching for 7 seconds and then take it out to air cool to about 130F.....slight marquenching I guess. You apparently have good success with taking it out of quench after 7 seconds, maybe straighten if need be and then putting it back in quench....which I can certainly try.

3) I will preheat my tempering oven and not worry about "how" I let the blade cool to room temp.
I was going to attempt to achieve a RC of about 58-59 but maybe 60-61 would be OK.....not sure.

4) Do you use or need to use any ATP-641 on your 1095 blades?

Just so you and others are aware, I am going to be making some hunting fixed blade knives of my own design and thought that 58-59 RC might be about right, again time will tell and, of course, other's opinions based on experience with 1095 for this type of knife. I will be using 5/32" 1095 stock and the knives will be 1" and 1.125" wide X 3.750" and 4" long blade minus handle length.

Thanks for the compliment regarding my attitude about knife making and "diving into this head first".
Please keep in mind, I don't dive into anything without first doing my homework and research. I've been around the block a few times as they say....especially at my age! If you really knew me and how I operate and the things I've done and accomplished, you would know I wouldn't ever attempt something I didn't feel very confident about regarding my ability to have success at.

I really shouldn't go into my background too much here, but I will a little.........
Some of my God given talents and skills involve anything mechanical or electro/mechanical. My mediums of choice are steel and wood and anything with an internal combustion motor. I'm also good at gunsmithing and even took a course. I've learned a lot in my years from some schooling, self taught research and much hands on. I realize where my skills and talents lie and where they don't. I love hunting, guns, knives and motors, making or repairing anything myself, etc., etc. I built my entire log house from top to bottom myself including wiring and plumbing and finish work. If I didn't think I could make knives and make them well with practice......I wouldn't be doing this. At my age I already know what I like and what I'm capable of (and not capable of), one of the few advantages of getting old!! As long as my body and mind hold out I will be doing these things I love, including riding my Triumph.
I learn something new everyday and we all have our gifts and talents and our bad points too! Us older guys just already know these things about ourselves and I for one don't have a problem admitting what my bad points are........which I won't go into here!

David Eye 01-22-2016 07:29 PM

I've been doing some additional research regarding 1095 possible grain growth during HT.

Correct me if I'm wrong, but I found a past statement by Kevin Cashen bladesmith that refers to 1095 and grain growth.
I believe he stated that there is no grain growth with 1095 until 1525F or more and that we shouldn't worry about grain growth during somewhat extended periods of time at lower temperatures!
If that is the case, then it really shouldn't matter if I put a room temp 1095 blade in a cold elect. kiln and heat it up to 1475F at a slower rate and then soak it at 1475F for about 10 minutes. I would only want to do it this way in order to BE SURE that my blade is at 1475F BEFORE the 10 minute soak.

I am now not sure which method (preheat kiln or not) to use and which may be best and easiest in order to MAKE SURE my blade is at 1475F BEFORE soaking for 10 minutes!

I DON'T want to offend anyone, I just want to do what's best to achieve the best results consistently for 1095. The same holds true for the 1095 quenching method. As I stated earlier, I realize different techniques can come into play with heat treating and what works for one person may not work that well for another due to many variables. But.......there must be a general consensus regarding preheating the electric kiln or not before putting the 1095 blade in. And a basic consensus on quenching method when quenching 1095 in Canola oil, even if it isn't the best quench oil.

It might be easier said (asked) than actually getting a general consensus on these two things.
I'll wait and see what develops and who else might feel like chiming in here!
I still want to thank you, Stuart, for all your info and help and telling me what works for you.....I really do appreciate it.

Doug Lester 01-22-2016 10:10 PM

I started out with 1095 from Admiral. I didn't use canola oil but I did use what is referred to as Goddard's Goop and it just wasn't fast enough. I had to resort to brine. I think that most makers on these boards who still use 1095 at least use a purpose made rapid quenching oil.

As far as quenching goes I would also recommend that you start out at 400? and then test the edge. If it is too hard you can always boost the temp up by 25? and do another cycle until you get the performance that you want out of that blade. You then make a note of that for future blades made with your equipment. If you make the blade too soft by starting out with a higher tempering temperature you will have to repeat the hardening process and decrease the tempering temperature to find the sweet spot. It's just easier to sneak up on the right temperature from below than from above.


David Eye 01-23-2016 08:06 AM

Doug, Thanks for the pointers. I agree with you about sneaking up on the correct tempering temp in order to get the correct hardness. I'm just not sure what the consensus is regarding RC for my type of blade using 1095. Yes, I can do some testing myself and make a determination.

I will be trying Canola oil first, from what I have read some people seem to have pretty good success.

On another note:
I was doing some additional thinking last night on the "preheat" versus "not preheat" kiln question.
I'm thinking a possible good alternative might be to preheat my kiln to approx. 1000 to 1200F and then put my blade in and heat up to 1475F and soak for 10 minutes. This should give my blade some extra time to get to 1475F. This method MIGHT be a good compromise and the blade wouldn't be in the kiln as long as from cold.....even though may not be a worry regarding grain growth.
As I said, I'm just not sure how much actual time my blade will need to get to 1475F if I only put it in the kiln when the kiln reaches 1475F and then rebounds back to 1475F. Since I have never done that (or any method) I'm thinking it won't take my kiln long at all to rebound to 1475F and the blade might not be totally saturated to 1475F.........not sure, just a thought.


Doug Lester 01-23-2016 04:46 PM

As you have noted from Kevin Cashen's work that if you hold the 1095 under 1500? the length of soak will not have a negative effect on grain growth even on that simple of a steel. Another thing to consider is putting too much carbon into solution which I don't think is a problem if you keep your austenizing temperature down to around 1450-1475 the length of soak doesn't mean that much. Anyway, if you did form too much retained austenite you can correct for it with multiple tempering cycles. I wouldn't recommend cryo-treatment for something as simple as 1095. All you will be doing is just making your steel cold.

One thing on measuring HRc on 1095. It's a shallow hardening steel and, depending on the fineness of the grain, is self limiting as to how far through the the blade it will harden, basically twice the depth of penetration on something the thinness of a knife blade. This means that even though the edge may will harden up to, let's say, 1/8" thickness, the spine and the ricasso won't harden at all. That means you won't have two parallel surfaces for the HRc tester that are hardened. Ways around that are to make a coupon that is slightly less than 1/8" and heat treat it and test it or you can use the calibrated hardness testing files on the edge. I know the latter is rather crude but it might be all that is available to you.


David Eye 01-23-2016 09:45 PM

Thanks Doug, I appreciate the comments and info.
I was never planning on a cryo treatment.....I knew it was not the best or needed with 1095.
I am planning on a test "coupon" as they say and a ground/beveled blade sample to harden. Believe it or not, I already knew from my research that 1095 was a shallow hardening steel. The thickest part of my blades will not be over 5/32" (actually slightly under) so shouldn't be too bad regarding depth.....time will tell.
I also happen to have some hardness files from my nephew. I know they aren't the best and rather crude, but they may help me out somewhat.

Doug Lester 01-23-2016 11:39 PM

Considering the conditions that you have to operate a regular hardness tester at and their expense, files are just about what most of us can handle. I know I don't have access to a lab that has a tester or a shop room that has the atmosphere needed to set on up in. They're better than nothing.


David Eye 01-24-2016 07:59 AM

Besides the hardness files I was also planning on doing the brass rod roll test on the knife least on my test blade(s) and future "lots" of steel or if I make changes to my HT procedure.
My nephew used to have a really nice hardness tester, but it was stolen when they closed down.

Doug Lester 01-24-2016 01:59 PM

I would recommend that you do something like the brass rod test with each knife that you produce to assure that everything went alright in the heat treating process. It's non-destructive and would help avoid putting out a sub par knife.


Andrew Garrett 01-25-2016 10:03 AM

I always find the 1095 discussions interesting. I've been using it since 2005 when I started out.

I have a Paragon KM-24D but I choose to HT all my carbon steel blades in an atmospheric forge.

I've attempted some sort of controlled soak at critical temp, but have not found measurable differences in 'as quenched' hardness or grain size.

Mt standard HT involves a blade which is 80%-90% ground (bevels) to 120G (220 every now and then).
I pack the spine with wet Satanite (refractory cement) to about 3/16" thick.
I put it in the running forge with no delay. The cement is still wet.
I do not set it down. I hold it with my tongs and closely monitor the blade visually. The tip gets hot first and must be dipped in the quench oil a few times as the rest of the blade edge comes up to temp.
When the color is getting close (dull dark red), I start testing against the hanging magnet. Once it is not magnetic along the entire edge and the color is even, I put it back in the forge for just a second to get back to the correct temp (it lost a few degrees testing against the magnet), then it goes directly into the quench.
The most important part of quenching any carbon steel and especially 1095, is properly preheated oil. Mine is peanut oil heated to 120*. This prevents the hot blade from 'sizzling' in the cold oil and forming a 'vapor jacket' around the blade (which needs to be in contact with warm oil not hot air).
After a second or three in the warm oil, I begin to slowly move the blade carefully fore and aft in the quench tank exposing it to the areas of 120* oil rather than the oil directly around where it went in (now considerably hotter). It is very important that you do not 'paddle' the blade in the oil as it is moving. You want each side of the blade to experience the same temps at the same time. Otherwise, warpage can and will occur.
After about a minute or so of careful fore and aft movement, I pull it out, use pliers to carefully crumble away any remaining Satanite, and then wire brush the blade before a final paper towel wipe.

If I am planning a hardness test on my Rockwell tester, I will have gone to 220 grit or even 400 to allow the penetrator a flatter surface and not a microscopic 'valley' the width of the penetrator tip. A quick rub down with the same grit paper to remove carbonization on the surface and its ready for the tester.

Here's the thing with Rockwell testers (at least mine): It's tough to get an accurate reading on a beveled surface, especially one beveled on both sides. The anvil on the tester is flat. A hollow grind will leave open space under the spot being tested which will destroy the reading and possibly the blade if it is brittle enough at this point. Don't ask me how I know that.
Thus, hollow ground blades at my shop get file tested. After all these years, I've become accustomed to the 'correct' sound and feel it should make.

Moral of the story: 1095 is fine. I've been making hard-use knives out of it for years (one in my pocket as I type this). It makes a decent hamon too. Just be sure to warm up that quench oil (I use forge heated scrap steel to do this). It will actually be 'hot' to the touch at 120*. You will think it is too hot to quench the first time or two, but it isn't.

If you are making a batch of blades, don't allow the oil to get too hot after the first couple. Allow it time to cool back down and check it with a quality thermometer.

David Eye 01-25-2016 10:30 AM

Thanks for all the info, is appreciated.
Very useful info that definitely agrees with most of my research, most I knew some I didn't.
I'm sure other's will benefit also from your informative write up.

I, of course, will NOT be using an atmospheric forge.....only my electric kiln, so much of your method of HT I won't be able to do the same.
I'm still wondering about some less expensive home brew anti-scale compounds and also if I could just use the store bought refractory cement (thinned out) made by Meeco.
Thanks again,

samuraistuart 01-25-2016 02:01 PM

Hey David, believe it or not I forgot which forum this thread was in, and so I got lost!

Doug Lester, as you can tell, is a great guy to talk to and knows his stuff, as well as Andy

Looks like one of your concerns is about the blade placed in a warm or cold kiln. To place the blade in first, then turn the kiln on, I don't really think there is anything inherently wrong with that approach, but two things that I can recall immediately with such a procedure...
1. The blade will have more decarb to be removed if you don't have it protected with anti scale compound. (no help with home made stuff....I use ATP 641)
2. I have always heard that the best grain structure is achieved when a rapid heat is used, instead of slowly coming up to critical. No experience one way or the other, but that is what is taught (best to have the kiln warmed up first)

About the soak times and rebound of the temp readout, etc. Yeah, I think you're slightly overthinking it. OK let's say we have oven at 1475 ready to go. We insert our blade and we need a 10 minute soak. The readout will drop maybe 10-20 degrees due to the cold mass of the blade, and will rebound in a minute or two back to 1475. It may only take 15 or 30 second to rebound back to 1475, this will depend on your kiln and the mass of the blade. Sure, the thermo couple will be telling you it's back to 1475 while the blade is still warming up to 1475. But we're only talking a minute or two for the blade to come up to temp. So technically, yes, if it takes 2 minutes to come up to 1475, and the thermo couple has already come back to 1475 in 30 seconds, then you're soak would be, technically, a minute and a half short of 10 minutes. But in the scheme of things.....that's nothing to worry about. If it bugs you, do a 12 minute soak instead.

Hope that helps some.

David Eye 01-25-2016 03:37 PM

Thanks Stuart....appreciated.
What I'm not sure of is how long it will take the blade to actually be completely saturated to 1475F when I put it into a preheated oven. You say only a couple minutes....are you absolutely sure? How are you determining color when you take it out? You say preheated oven is "what is taught", maybe for less chance of grain growth, but where did you get the info? Kevin Cashen stated that there really should be no concern regarding 1095 grain growth as long as the temps are kept below 1525F. I know grain growth can be a problem with other steels and I'm not debating that, but I'm trying to keep this about 1095.

Yes,I am concerned about scale and decarb especially due to a longer time in the kiln, thus the reason I want to use an anti-scale compound. If I have to purchase ATP-641 I will, I was just hoping for something a little less expensive and maybe a home brew of some kind.

If the blade heats up as quickly as you say when put into a completely hot (1475F) kiln, then as I mentioned before, I was thinking of a slight compromise to be SURE the blade is @1475F BEFORE my soak. Mt compromise would be to put the blade in at maybe 900-1200F instead.

One thing I hate is "MAYBE'S" when it comes to something I would like to be more exacting on.
I did look at the Paragon and Evenheat instruction manuals for their Knife blade kilns and they state to put the blade in a cold kiln, although they might not be completely learned on all aspects of Heat Treating various steels, such as 1095 versus stainless, grain growth possibilities between steel types, etc, etc.

I personally don't believe I am "overthinking" anything regarding wanting to be sure the blade is saturated to 1475F before the soak. I believe it is VERY important to be SURE the blade is up to temp before the soak. What "bugs me" is NOT KNOWING FOR SURE the amount of time it may actually take for the blade to get to 1475F with your method. Therefore I would rather play it safe and allow it MORE than just maybe 2 minutes to get up to temp and then soak.

What seems to be lost here is my NEED to be more exacting with my HT method. As I said earlier, that is my nature and with Heat Treatment of my blades I for sure will be as exacting as possible. One of the reasons I am building an elect. kiln is so that I can control the temp and time as precisely as possible. After all, HT really is all about temp and time for each given steel and it's properties.
I was hoping to gather some more definitive answers to just a few questions I had, but I'm beginning to see that that may not be very possible with so many people having their own techniques.
I'd rather stick to the known science and properties of 1095 regarding HT but at the same time introduce peoples own techniques based on experience with 1095. Yes, I'm a complete newbie at HT knife blades, but I'm not new at reasoning things out and making my own choices, at least to start out with, therefore:

1) I think I'd like to believe K.Cashen's statements about 1095 grain growth.
2) I want to be absolutely sure my blade is up to temp before the soak.
3) I was always planning on using an anti-scale compound of some kind anyway.
4) 1475F is not being disputed by anyone.
5) Soak time of approx. 5-10 minutes is not terribly disagreeable, although some people only soak a couple minutes.
6) Canola oil is NOT optimum quench medium but doable by many.
7) Temper temperature and RC value remains to be seen and I will start at 400F.

I really do appreciate any and all help from everyone, but I may not always agree with everyone's techniques due to my more exacting/precise nature.
Once I start heat treating blades I will be learning what works best for me to achieve properly treated 1095 blades. To borrow a cliche'....."the proof is in the pudding" (blade)!

Thanks to all again and I still welcome any and all help regarding HT of 1095.

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