Under, over, adequate, and superior heat treating

D

DevinT

Joined
Jan 29, 2010
Messages
2,641
Heat treating is a sensitive subject, offer advice on almost any aspect of knife making and you won’t get the pushback that comes from telling a maker his heat treat is bad.

I personally overstep my bounds way too often on this subject, I apologize.

Under heat treating is when you don’t do enough to get a good heat treatment.

Over heat treating is when you go to extremes thinking that you are getting more out of a steel than is possible. Quadruple normalizing, triple annealing, triple quenching, multiple cryo treatments, multiple tempers, etc…

Adequate heat treating is doing just enough to get good repeatable results.

Superior heat treating comes from testing and practice. Understanding a particular alloy and using the right equipment, temperatures, soak times, starting from the correct prior condition, cryo, adequate tempering, preventing oxidation, achieving balance between toughness and wear resistance etc…

There is probably not a big jump from adequate to superior heat treatment, some alloys respond more than others.

I highly recommend that anyone interested study the research already done before trying to come up with any new methods.

Sometimes heat treating is shortened to just austenitizing, quench and temper.

Forging, normalizing, annealing, hardening, cryo, and tempering are all important steps.

Correct heat treating will give a maker peace of mind and confidence.

Heat treating is one of the more exciting parts of knife making.

Good luck

Hoss
 
Spot on - and repeatable results are needed. That requires being able to hold a specific temperature for a set time. Knowing the temperature is hard in a forge and holding the same temperature requires a very good forge. I suspect most of us don't have a forge with that ability. I like my oven.
 
Devin, I appreciate your posts as much or more that any member on this forum. I don't feel you've ever overstepped, you know what you're talking about, your results are PROVEN by time and testing. You, like my dad, can say more in ten words than many people can in ten long winded paragraphs.
Every time you write I learn something or I'm reminded of something you taught me previously. I'm grateful and owe you more than I could ever repay.
 
DevinT said:
Heat treating is a sensitive subject, offer advice on almost any aspect of knife making and you won’t get the pushback that comes from telling a maker his heat treat is bad.

I personally overstep my bounds way too often on this subject, I apologize.

Under heat treating is when you don’t do enough to get a good heat treatment.

Over heat treating is when you go to extremes thinking that you are getting more out of a steel than is possible. Quadruple normalizing, triple annealing, triple quenching, multiple cryo treatments, multiple tempers, etc…

Adequate heat treating is doing just enough to get good repeatable results.

Superior heat treating comes from testing and practice. Understanding a particular alloy and using the right equipment, temperatures, soak times, starting from the correct prior condition, cryo, adequate tempering, preventing oxidation, achieving balance between toughness and wear resistance etc…

There is probably not a big jump from adequate to superior heat treatment, some alloys respond more than others.

I highly recommend that anyone interested study the research already done before trying to come up with any new methods.

Sometimes heat treating is shortened to just austenitizing, quench and temper.

Forging, normalizing, annealing, hardening, cryo, and tempering are all important steps.

Correct heat treating will give a maker peace of mind and confidence.

Heat treating is one of the more exciting parts of knife making.

Good luck

Hoss
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I have learned a lot from this site, and really appreciate the information folks post on here, including you Hoss. Your one of the many folks on here that has probably forgotten more than I know about knife making. Feel free to critique my work or offer any advice that could point me in the right direction.
 
DevinT said:
Heat treating is a sensitive subject, offer advice on almost any aspect of knife making and you won’t get the pushback that comes from telling a maker his heat treat is bad.

I personally overstep my bounds way too often on this subject, I apologize.

Under heat treating is when you don’t do enough to get a good heat treatment.

Over heat treating is when you go to extremes thinking that you are getting more out of a steel than is possible. Quadruple normalizing, triple annealing, triple quenching, multiple cryo treatments, multiple tempers, etc…

Adequate heat treating is doing just enough to get good repeatable results.

Superior heat treating comes from testing and practice. Understanding a particular alloy and using the right equipment, temperatures, soak times, starting from the correct prior condition, cryo, adequate tempering, preventing oxidation, achieving balance between toughness and wear resistance etc…

There is probably not a big jump from adequate to superior heat treatment, some alloys respond more than others.

I highly recommend that anyone interested study the research already done before trying to come up with any new methods.

Sometimes heat treating is shortened to just austenitizing, quench and temper.

Forging, normalizing, annealing, hardening, cryo, and tempering are all important steps.

Correct heat treating will give a maker peace of mind and confidence.

Heat treating is one of the more exciting parts of knife making.

Good luck

Hoss
Click to expand...

For an old man with aging issues, unable to learn anything new, you seem to still do okay there, Hoss. 🤣

I'll listen each and every time, along with a bazillion others. Thanks, Man!
 
I always appreciate your posts, seeing your advice constantly is what helped me decide to invest in a kiln and go from saying I think my results are consistent to I know my results are consistent. Heat treating is one of the most important parts of making a good knife and is something that has a lot of mysticism attached to it. It’s really nice seeing your no nonsense advice that is straightforward and comes from experience.
 
Your advice is extremely valuable, and your experience is without question. You have been successful in this industry longer than many of us members have been alive.

With that being said, I believe Bladefourms shop talk in general could be a bit more aware of the audience before automatically recommending a HT oven or overly harsh critiques of HTs. Burn at the stake the guy that brags he can HT anything in his forge and sells garbage all the time, but don’t take the wind out of the sails of a poor young maker that wants to try to make a knife with an angle grinder and a lump of coals in his backyard for fun. This is not specific to you but more of an observation in general of shoptalk regarding this topic. Obviously, these are two examples that are at the ends of the spectrum, but you get the idea.
 
If I were to use a forge for heat treating, I would build one specifically designed for heat treating. I would use a 30 gallon drum with a small burner, insulated with ceramic blanket and fit with a suitable thermocouple. Run it vertically and probably hang the blade from the top.

Travis Wuertz has been doing some innovative work with burners and controls for even heating at lower temperatures, looks promising.

I’ve yet to see a forge designed for damascus or forging of steels that was good for heat treating. They have hot spots and cold spots, heat too fast and don’t idle well at the temperature needed for most carbon and low alloy steels.

Most smiths seem to want to overheat the blades.

Japanese smiths tend to heat treat at the same time of day each time and darken the windows.

I’ve seen testing of coupons heat treated in a forge with a baffle and a thermocouple that tested very poorly.

It’s difficult to learn heat treating in a forge.

Hoss
 
The best, ONLY, way to optimize any process is to eliminate variables and undesirables. Chatter in your lathe or mill work? Look at rigidity first. Inconsistent or poor results heat treating? Use known steel, and control time/temperature first.
 
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DevinT said:
Superior heat treating comes from testing and practice. Understanding a particular alloy and using the right equipment, temperatures, soak times, starting from the correct prior condition, cryo, adequate tempering, preventing oxidation, achieving balance between toughness and wear resistance etc…

There is probably not a big jump from adequate to superior heat treatment, some alloys respond more than others.
Click to expand...

I've often mused with myself and my other knifemaker friend about what counts as "adequate" heat treatment. In my knife making journey I started out heat treating in a coal forge (by color), then I used a gas forge (using a magnet), then I got a heat treat oven, and then I got a rockwell hardness tester (this is over the course of 12 years). When I got the HRC tester I tested every knife I've ever made, just for kicks. What I found was that the knives I've heat treated in the forge were generally not what I expected in terms of hardness. Knives I thought were 60rc were closer to 50rc. They seemed to pass the file test coming out of the quench.
Were those knives "adequate"? When I was blissfully unaware of their actual hardness, I thought they performed pretty well. Now, armed with an actual way to test them, I would consider their heat treatment a failure.
 
SirSpice said:
Were those knives "adequate"? When I was blissfully unaware of their actual hardness, I thought they performed pretty well. Now, armed with an actual way to test them, I would consider their heat treatment a failure.
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Adequate? It really depends...
Did they do the job that they were designed to do? Did they do it well enough to justify the expense of making them? If so, then I say it's adequate... Superior? No.
 
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SirSpice said:
I've often mused with myself and my other knifemaker friend about what counts as "adequate" heat treatment. In my knife making journey I started out heat treating in a coal forge (by color), then I used a gas forge (using a magnet), then I got a heat treat oven, and then I got a rockwell hardness tester (this is over the course of 12 years). When I got the HRC tester I tested every knife I've ever made, just for kicks. What I found was that the knives I've heat treated in the forge were generally not what I expected in terms of hardness. Knives I thought were 60rc were closer to 50rc. They seemed to pass the file test coming out of the quench.
Were those knives "adequate"? When I was blissfully unaware of their actual hardness, I thought they performed pretty well. Now, armed with an actual way to test them, I would consider their heat treatment a failure.
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Probably not adequate because they were under hardened.

Good job improving over the years. It’s probably similar to a lot of makers.

Hoss
 
for me to be able to achieve superior heat treatment consistently, there are a lot of largely uncontrollable variables afflicting my shop. The biggest of which is ambient temperature, since I have no way of regulating the temperature of my work shop currently. To my, (newb) way of thinking, heat treating steel is all about precision- the more precision, the better and more repeatable the outcome. There are a lot of knowns- more than unknowns- when it comes to steel, so the more control one can exert over all the variables the better. I'm fine with adequate- if my knives perform well then I'm happy. I know that there's always room for improvement; handle ergonomics, weight distribution, cutting dynamics...I've experienced knives that fell short in one or more of those categories, which in my view would render a superior heat treatment moot. Obviously, we all want to make a knife perfect in every way, but I think we all know that that will never happen.

The most important investment I made in my shop was an evenheat. Yes, more important than my 2x72. I have and would continue to make knives with hand tools, but I always felt weird outsourcing the one thing that would turn my hard work into something worth having. Not to mention the time and hassle it takes to outsource it. Time and hassle I'd rather spend making shit. So for anyone out there wondering what size/type of grinder, what abrasives, what mini mill, what surface grinder...I say start with a reliable oven first and move on from there.

I'm just blabbing here, so take it for what it's worth
 
I'll be totally honest. You "overstepping your bounds", and its embarrassing to admit, as a grown man. Hurting my feelings a bit. Is probably one of the biggest factors in what drove me to go ahead, and move toward using more controlled methods than I was, and contuing to put more effort into improving what I currently have now (which is much better than what I was using).

So, for what it's worth. Thanks for not being afraid to, and getting tired of putting your advice out there for people like me who need it.
 
After paying for the first round of blanks to be HTed externally with specified hardness, I figured that with some patience I can get a used HT oven for the price of next 3 batches. Hardness tester costed me another 2 batches of external HT. In the meantime I did those 5 batches and equalled the cost. First thing I did I checked the hardness of all externally HT blanks, on average they were all 2 HRC below requested hardness. I can also use oven to warm up pizza in between, so its really a win-win situation. Unless you almost burn the whole place with pizza bursting in flames.
 
well, D DevinT , I researched some of your past wisdoms and had myself a pretty successful run at this AEB-L today.
Thank you for your contributions! Really helped me out :thumbsup:
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