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1  KNIFE TALK / General Discussion / Re: a question about the quench curve on: May 17, 2016, 09:42:07 AM
Oil quenching fully hardened blades tends to pull the point down, like you saw.  Water quenching clay coated blades tends to push the point up.  It's all in what cools first compared to everything else.  There can be a lot going on.  See below.

2  KNIFE TALK / High Endurance Knife Discussion / Re: some interesting information on: April 14, 2016, 10:07:20 AM
The high sulfur content is indicative of low quality steel the vanadium was added to make it hard cheap.

I have heard others mention using our methods on different steels, but was not sure they followed what we do. With Jared teaching him I know Nate followed our methods right down the line, from the first hammer blow to the final polish. I have seen the fished blades and they look good.

While I only worked on high quality steel once I found out what high quality steel was, I had no idea that you could realize what I consider high endurance performance blades with lower quality steels.

I am proud of Jared and Nate for working with this steel, it if obvious they did a good job as proven by the performance qualities that are obvious by their testing. When we take our time and put a little extra effort into the development of our blades it may very well be worth it. But we will never know if we don't test.

That's a fairly typical amount of sulfur in modern steels.  How does adding that small amount of vanadium make the steel harder?  Even with as little as 0.45% carbon, the increased hardness when quenched and tempered will far overshadow any effect that little vanadium will have.  Was it a particularly high number of tramp/trace elements that made it "dirty," or maybe too many oxide or other inclusions when viewed under magnification?
3  KNIFE TALK / High Endurance Knife Discussion / Re: some interesting information on: April 10, 2016, 12:05:09 PM
Any idea of the details on the heat treatment of the 1045V?  Any elaboration on "make it hard cheap" or what "poor quality and dirty" meant?
4  KNIFE TALK / General Discussion / Re: Comparing knives: custom vs production? on: March 05, 2016, 11:06:36 AM
Has anyone done comparative testing between the best production knives to see if they hold up to the hype? - ex. Busse's Infi steel claims to be "nuclear tough" and has a huge following.  Does it equal or excell against differentially heat treated 52100 in a full range of tests, including destructive?  Or, is it unfair to compare these against one another?

For the sole maker, is there no incentive to do comparative tests? And to report the results, is this in bad taste, knowing it could lead a company to change its processes or harm the individual knife makers reputation? Isnt the idea having objective comparative results ultimately good for the consumer, and everyone? Why not start up a performance rating for knives?  -Ed mentioned this several years ago in a Blade seminar.
Thanks in advance.
Interesting YouTube videos, bark river related:


There is a lot going on there.  I see nothing wrong with testing knives and comparing them to one another, even production vs. custom.  However, one must be aware that knives are designed with different goals in mind.  Most knives are not intended to flex to any degree laterally, as that doesn't have much benefit to their intended purpose of cutting.  I think a more fair comparison is of knives marketed for similar groups of uses.  The best way I've found is to ask a maker what the knife is supposed to do well, then test for that vs. other knives that are marketed for the same uses. 

I have been doing testing with mostly very inexpensive knives for a few months now.  What I have found is most knives will cut much longer than most people think, and that sharpening has a huge influence on how well a knife cuts.  The chopstick thing came from a knife billed as a high quality knife not being able to whittle a chopstick without damage.  No one I know of make knives specifically for chopstick cutting, but if a knife is billed as an outdoor knife and can't do it, it's a pretty poor outdoor knife.  Cutting a chopstick is more stressful to an edge than cutting a 2x4 or 4x4.  I have knives that would chop through boards, branches, etc with little issue, but chopping smaller sticks, such as brush 1/4" or so, would dent the edge.  Now, there was a problem with those knives and that's the reason I no longer recommend power sharpening, but chopping a chopstick size piece of wood was able to tell me what cutting other lumber and branches missed. 
5  KNIFE TALK / General Discussion / Re: quenchant??? on: February 05, 2016, 05:20:03 PM
" Lower carbon dissolved into solution also means less retained austenite to deal with later. "

How do you deal with it later?

Continuing the quench below room temperature is one way.  Dry ice and liquid nitrogen are common enough.  It can also be done during tempering, which is highly dependent on steel type and temperatures.
6  KNIFE TALK / General Discussion / Re: quenchant??? on: February 03, 2016, 08:06:10 PM
Yea Joe, that's him. 

John, I checked his procedure and he does a mix of thermal cycles, some with a air cool, and some with an oil quench, maybe 4 or 5 cycles.  I didn't see a definite number.  He also does an initial grain refining step at high enough temperature to dissolve all the carbides.  Hardening is done at low temperature, so maybe as low as 1400?F to 1450?F.  Blades are quenched in Superquench, cooled to 0 F, and tempered low, 325? in some cases.  The target hardness on the one I have was 63 HRc. 

what's 50 points carbon ?  is that more than 52100 for example with 1.0 carbon ?

i used to super quench everything - till i had a run of cracked blades - all flat ground - got some oil from Ed after that.

No, not more than 52100, since he's using 52100.  What he's talking about is the amount of carbon in solution (as opposed to the amount that is forming carbides).  Of the 1% carbon in 52100, he's trying to get 0.50% into solution, leaving the rest to form those very small carbides he's worked so hard to make.  The cracking is the risk you run with using superquench.  However, if you keep careful control of the temperature before quenching and refine the grain size, and refine the carbide size, you can mitigate the risk.  Less carbon dissolved into solution means less risk of cracking.  Smaller grain size means less risk of cracking.  You only need about 0.55% (give or take) to get hardness up around 64 after quenching, particularly if you cool below room temperature.  Tempered hardness can still be well above 60, with very small grains, and very small and well dispersed carbides.  Lower carbon dissolved into solution also means less retained austenite to deal with later. 
7  KNIFE TALK / General Discussion / Re: quenchant??? on: February 03, 2016, 05:35:57 AM
Yea Joe, that's him. 

John, I checked his procedure and he does a mix of thermal cycles, some with a air cool, and some with an oil quench, maybe 4 or 5 cycles.  I didn't see a definite number.  He also does an initial grain refining step at high enough temperature to dissolve all the carbides.  Hardening is done at low temperature, so maybe as low as 1400?F to 1450?F.  Blades are quenched in Superquench, cooled to 0 F, and tempered low, 325? in some cases.  The target hardness on the one I have was 63 HRc. 
8  KNIFE TALK / General Discussion / Re: quenchant??? on: January 31, 2016, 07:11:00 PM
I will have to be the one to dissent.  I have a blade made by Luong Lu in California that was quenched in Superquench, which is a faster quenchant than ice brine (salt water).  The blade cuts very well, sharpens easily, and holds an edge quite well.  

Here's the theory on this, and I find it to be sound, though I'm still somewhat skeptical of some claims.  Luong does grain refining and carbide refining treatments and claims grain size similar to Ed's ASTM Size 14.  He also uses an oven and uses a hardening temperature of around 1425-1450 or so.  I'll have to double check this.  He also claims that his performance decreased as his grain size decreased.  What he found was that faster quenchants increased the performance.  His theory is that as the grains size decreases, the quenchant speed must increase in order to achieve full hardness out of the quench.  Now, I have not done extensive testing, as the knife is a loaner, but it shows better edge retention than the test knife I compared it to, though to be fair, the test knife had sharpening issues.  

Luong's theory is sound, as it is well known that grain size has a profound influence on the required quenching speed for fully hardening the steel.  Coarse grains harden more easily, finer grains require faster quenching to reach full hardness.  Even though steels like 52100 have chromium and some other elements added to allow full hardening with slower quenchants, the reduction of grain size can still overshadow them if refined very small.  Also, though not relevant to this discussion, Luong also chooses the hardening temperature to provide the minimum carbon to reach maximum hardness, minimize retained austenite, and tempers to higher than usual hardnesses, avoiding the embrittlement zone between 450 F and 650 F common to low alloy steels.

I say all that to say that different quenchants are not unique to a different steel, but depend on the microstructure present in the steel prior to quenching.  If you find your blades do not perform as you want, you may want to change your procedure or your quenchant.  If you try a slow oil, switching to a faster one, or using the Parks 50 you already have, may show some gains.

I also find it interesting that 2 makers take opposite approaches in terms of quenching speed and still get good performance. 
9  KNIFE TALK / General Discussion / Re: 5160 fillet knife ? on: December 08, 2015, 11:09:11 AM
I've done some work on knives that were 0.03" at the spine.  They will move on you if you push on them.  How thick is the spine on that fillet knife?  One has to define flexibility first to see what I mean.  Flexibility implies a return to straight, particularly in this case of discussing a fillet knife.  Bending implies it stays where you put it after the test.  If you test for flex before heat treating, and the spine is thin, it will likely bend and stay there.  However, if you test for flex after you harden it, two things are possible.  It will flex further before bending than it did when it was soft, and it will return to straight from a greater flex.  So, do you want to know if the fillet knife will return to straight after being flexed?  If so, check it after heat treatment. 

To put some made up numbers to this, take a desired flex of 90 degrees.  If you try before it's heat treated, it will almost certainly bend to 90 degrees with no trouble.  When you let it go, it will recover a little, but mostly it will stay put where you flexed it. 

If you heat treat it first, and the spine is thin enough, it will flex to 90 degrees and spring all the way back straight.  I have done this on blades as hard as HRc 65 and 0.04" thick.  If the spine is too thick, it will break.  However, the thicker spine will require more effort to flex to 90 degrees.  As the hardness comes down to say 55-60 HRc, you will see some bending and less chance to spring back to straight.  I have tested knives 1/16" thick and they flexed to 90 degrees, didn't crack, and returned to within 10 degrees or less of straight.  These were hardened in the mid 50's HRc.  These were production knives.  The high hardness blade above was one I made from scrap saw blades, but were not heat treated by me.
10  KNIFE TALK / General Discussion / Re: Hot Oil and Hardening temps on: November 22, 2015, 01:35:50 PM
It's interesting to note that relatively slow oil (Texaco Type A) is often recommended here, along with the grain refining treatments common among makers here.  Dedicated quenching oils generally have a target range where cooling is optimal, and the range is fairly broad, between room temperature and 170 degrees F.  Specific ones are intended to be used in certain temperatures.  Using them outside their range may not give poor results, but may result in the oil breaking down faster than normal or other changes that are not desirable.

It is also interesting that this thread touches on cooling rates.  I have a couple of knives on the way from a maker that uses extremely fast (faster than brine) quenching on low alloy steels and claims superior performance in his tests.  We'll see what happens when I get them.  Should be mid December.

11  KNIFE TALK / General Discussion / Re: Another W2 on: October 28, 2015, 06:02:39 PM
Is that a change in grind on the tip?  If so, I really like stuff like that.  If not, I really like that stuff too.  The polish and hamon (maybe) are very nice.
12  KNIFE TALK / General Discussion / Re: Chris Broke his leg! on: October 28, 2015, 05:59:04 PM
Sounds like he's in good hands.  Best wishes for a fast recovery.
13  KNIFE TALK / General Discussion / Re: Chris Broke his leg! on: October 27, 2015, 07:38:10 AM
Well, that isn't good.  Provided his surgeon is good, he should be back up nearly normal in about 6 months.  I had a similar break about 5 years ago.  My surgeon was a spine surgeon, so I would give him a hard time about having an easy night when I got hurt.  Then I saw the people he had to take care of in his waiting room and told him I felt bad about taking up his time.  Those people were bad off.  As long as the nerve and artery weren't cut by the bone, he should be able to recover.  I lost a little mobility in my ankle, and a little flexibility in my knee, as far as being able to sit on my knees in the floor and such.  Overall, I'd say I came out pretty good.
14  KNIFE TALK / General Discussion / Re: Newbie question on: September 22, 2015, 11:07:23 AM
I don't know why a good hamon wouldn't work for HEPK purposes. I just don't know anyone that's tried it either.  The spine should be fine pearlite, while the edge will be hardened and tempered as desired.  There are a couple ways to do it, as it is strongly affected by grain size.
15  KNIFE TALK / General Discussion / Re: Spheroidized Steel on: September 21, 2015, 07:05:37 AM
I have...five...main questions about this:
-What is spheroidized steel? like what does it's structure and hardness look like?
It is steel where the iron carbides, or other carbides if present, has been treated to turn the carbides into relatively large spheres.  The hardness is extremely low, teens or low 20s rockwell.
-How is it achieved in steel?
It is achieved via heat treatment.  There are a couple or 3 ways to do it, depending on what steel and equipment are available.  Generally, one way is to hold the steel at 1200 to 1300 degrees for a couple of hours. 
-It seems there are coarse and fine states how are they different?
This is an educated guess, so take it for what it's worth.  The coarse and fine refers to the size and distance between the carbide spheres.  Fine has smaller spheres closer together.  Coarse is the opposite.
-how can you eliminate this condition?
Heat and time.  Another heat treatment, or sometimes it does not need to be eliminated.  Heavily spheroidized steels will have this condition removed during the heating and cooling of forging, or preparatory heat treatments before hardening.  A text book normalization, where all the carbides are dissolved, will surely do the trick.
-Why and when would you want it?
It is the most desirable structure for high carbon steels that will be machined.  The spheres are separated by considerable distance, and are less frequent, so they don't hit the cutters as often.  It saves considerable wear on tool bits and allows faster shaping.  If one were to only use files, or were to shape blades with a milling machine, this is the ideal state to have the steel in during shaping.  It's not the only state where these things can be accomplished, but if you're doing a lot of it, the benefits add up.  I don't know of anyone who has said either way, but if you are stamping blades out of a sheet of steel, I'd imagine this structure is the way to go for that as well.
Any advise about this would be great!
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