Acute angle certainly helps with improving cutting ability.Wartstein wrote: ↑Mon Jul 13, 2020 5:09 pmLarrin wrote: ↑Mon Jul 13, 2020 3:00 pmSerrated edges have poorer cutting ability but superior edge retention when slicing.
Edit: data is here - https://knifesteelnerds.com/2018/11/26/ ... etention2/
Larrin, " serrated edges having poorer cutting ability when slicing" is so contrary to my (admittedly total layman and non scientific!!) in-use-findings, that I may ask:
Could it be that I find Spydercos serrated edges to be even better slicers than their plain edges not because they are serrated, but because SE is ground to a much acuter angle (due to the chisel grind)?
13 Myths about Heat Treating Knives
Re: 13 Myths about Heat Treating Knives
http://www.KnifeSteelNerds.com - Steel Metallurgy topics related to knives
Re: 13 Myths about Heat Treating Knives
Another factor in slicing ability that doesn’t show up on a CATRA test is the greater ease in hand due to the serrations locking the blade into the media being cut. Preventing a plain edge from slipping out of heavy corrugated cardboard takes a noticeable effort. This effort is much reduced with FFG SE because the scallops and points help hold the blade in the cut as it proceeds.
Re: 13 Myths about Heat Treating Knives
If I understand the article he linked, I think the summary is SE is more effective at cutting even when worn.Wartstein wrote: ↑Mon Jul 13, 2020 5:09 pmLarrin, " serrated edges having poorer cutting ability when slicing" is so contrary to my (admittedly total layman and non scientific!!) in-use-findings, that I may ask:
Could it be that I find Spydercos serrated edges to be even better slicers than their plain edges not because they are serrated, but because SE is ground to a much acuter angle (due to the chisel grind)?
Chisel grinds aren’t necessarily more acute than a PE, it just depends on what angle the maker chooses to grind.
Re: 13 Myths about Heat Treating Knives
zhyla wrote: ↑Mon Jul 13, 2020 11:36 pmIf I understand the article he linked, I think the summary is SE is more effective at cutting even when worn.Wartstein wrote: ↑Mon Jul 13, 2020 5:09 pmLarrin, " serrated edges having poorer cutting ability when slicing" is so contrary to my (admittedly total layman and non scientific!!) in-use-findings, that I may ask:
Could it be that I find Spydercos serrated edges to be even better slicers than their plain edges not because they are serrated, but because SE is ground to a much acuter angle (due to the chisel grind)?
Chisel grinds aren’t necessarily more acute than a PE, it just depends on what angle the maker chooses to grind.
That's true of course. :)
But I was referring specifically to the chisel grind on Spydercos SE knives, those are always more acute than the V grinds on their PE knives as far as I know (so for example around 20 inklusive instead of 20 per side).
Top three going by pocket-time (update March 24):
- EDC: Endura thin red line ffg combo edge (VG10); Wayne Goddard PE (4V), Endela SE (VG10)
-Mountains/outdoors: Pac.Salt 1 SE (H1), Salt 2 SE (LC200N), and also Wayne Goddard PE (4V)
- EDC: Endura thin red line ffg combo edge (VG10); Wayne Goddard PE (4V), Endela SE (VG10)
-Mountains/outdoors: Pac.Salt 1 SE (H1), Salt 2 SE (LC200N), and also Wayne Goddard PE (4V)
Re: 13 Myths about Heat Treating Knives
Thanks for this post! I've gotten about half way through and I agree with everything you've said so far.
From the article you linked Wartstein to:
From the article you linked Wartstein to:
Why was the starting cutting ability of the serrated knife so much lower than the plain edge? Did they start with different sharpness levels? Or did it simply do a poor job cutting the cards on the catra test?There were also a few comparisons between a serrated and a “plain” or non-serrated edge. The serrated edges are typically at lower edge angles to improve their cutting ability relative to plain edges. The serrations mean the edge wears much more slowly than plain edges; the CATRA test is often performed with 200 cuts rather than the standard 60 because the edge wear is so much slower. The initial cutting ability of a serrated edge is significantly lower than a plain edge but after a sufficient number of cuts the serrated edge keeps going while the plain edge has dulled. Below I have a comparison with the same steel, one with a plain edge at 26° and the serrated with a 22° edge angle.
- Cambertree
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Re: 13 Myths about Heat Treating Knives
Vivi, my guess would be that perhaps the high points between the serration scallops cause more drag when being sliced into thick, binding media. At least, compared to a PE blade when both are freshly sharpened. Then, as the graph shows, SE takes over as the PE blade wears.
Just a guess, based on my own observations and use.
Just a guess, based on my own observations and use.
Re: 13 Myths about Heat Treating Knives
I think he's a great bladesmith, and his heat treatment is top notch and he can push for a nice balance of properties, particularly hardness (I own two knives heat treated by him), but it's nothing revolutionary, a 65-66hrc s110v knife by him still has the same properties and limits as another one at 65 done by some Russian guy that uses plate quench, and arguably the same crystalline structure/grain size etc if done right. His heat treatment is no different than what Big Brown Bear ends up with. Respectable and very good, but chemistry and physics don't change, they're the same for everyone no matter what steps you do during heat treatment. There's only so much you can influence with a heating curve and quenching/tempering.Pancake wrote: ↑Mon Jul 13, 2020 10:01 amI think you know about one blade forum member BluntCut (I think he is also here) and his crystal weaving foundation heat treat (or something like that). What are your thoughts on that? He claimed that he could HT some steel higher then anybody else on the planet (well, maybe not these exact words but close) and his HT include some swirling and slicing in quench oil to get the microstructure.
Great article, always a joy to read. Cheers!
Question for Larrin: How stable is martensite over time, at what we would call normal environment temperature (20-40 degrees celsius)? Is it's metastability just a scientific naming to be more accurate (in relation to truly stable states) and its actually stable for geological time frames, or does it switch to austenite over, quote marks, "short" periods of time?
Re: 13 Myths about Heat Treating Knives
Martensite decomposes to ferrite given enough time and temperature. We force this to occur all the time through tempering. A knife might be tempered at 400°F twice for 2 hours each time. The higher the tempering temperature the lower the hardness and the closer it gets to ferrite. Tempering is controlled by both time and temperature but because time is on a "log scale" the change with further increases in time beyond 2-6 hours is rather slow. This is represented by the Hollomon-Jaffe equation: https://en.wikipedia.org/wiki/Hollomon% ... _parameteremanuel wrote: ↑Tue Jul 14, 2020 3:33 amGreat article, always a joy to read. Cheers!
Question for Larrin: How stable is martensite over time, at what we would call normal environment temperature (20-40 degrees celsius)? Is it's metastability just a scientific naming to be more accurate (in relation to truly stable states) and its actually stable for geological time frames, or does it switch to austenite over, quote marks, "short" periods of time?
To start reducing hardness below the original target, we would need to temper beyond the original target. Re-tempering at 300°F for 2 hours would not appreciably affect a 400°F tempered knife, for example. So if we calculate the time required at room temperature to be equivalent to a 400°F 4 hour temper I calculate about a billion years. To have a more significant change, like an equivalent to a 450°F temper, I calculate 46 billion years.
http://www.KnifeSteelNerds.com - Steel Metallurgy topics related to knives
Re: 13 Myths about Heat Treating Knives
Very informative as usual! Thank you very much.
My response is "Just because you can't see it, doesn't mean it isn't there, it just means you can't see it". Sal G.
Re: 13 Myths about Heat Treating Knives
How about the effects of time on retained austenite converting into untempered martensite? There are legends out there for old blades changing hardness over time. Over periods of hundreds of years.
Re: 13 Myths about Heat Treating Knives
The retained austenite is presumably very low in old blades to begin with. For one thing, they are often not even quenched to martensite. More in the 40s Rc and pearlitic. I would need to see some rock-solid explanations for how they knew there was retained austenite hundreds of years ago but not today.
One other factor: there are two different transformations that can occur with retained austenite, decomposition and destabilization. Decomposition leads to "ferrite + carbides" or some type of bainite, not martensite. Destabilization usually occurs at higher temperatures and leads to the formation of martensite upon cooling. Decomposition is more common with low alloy steels with typical tempering temperatures. Which is what we would expect in old swords.
http://www.KnifeSteelNerds.com - Steel Metallurgy topics related to knives
- Tucson Tom
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Re: 13 Myths about Heat Treating Knives
I really enjoyed this article and think I learned more from it than from any of your articles, though I would do well to backtrack and reread some things. No doubt this says more about me than your writing, or maybe this article brought it down to a level I can wrap my head around. Anyway, thanks a lot.
- curlyhairedboy
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Re: 13 Myths about Heat Treating Knives
Great article, Larrin. A lot of these myths seem to arise out of not realizing just how many factors go into steel.
EDC Rotation: PITS, Damasteel Urban, Shaman, Ikuchi, Amalgam, CruCarta Shaman, Sage 5 LW, Serrated Caribbean Sheepsfoot CQI, XHP Shaman, M4/Micarta Shaman, 15v Shaman
Fixed Blades: Proficient, Magnacut Mule
Special and Sentimental: Southard, Squarehead LW, Ouroboros, Calendar Para 3 LW, 40th Anniversary Native, Ti Native, Calendar Watu, Tanto PM2
Would like to own again: CQI Caribbean Sheepsfoot PE, Watu
Wishlist: Magnacut, Shaman Sprints!
Fixed Blades: Proficient, Magnacut Mule
Special and Sentimental: Southard, Squarehead LW, Ouroboros, Calendar Para 3 LW, 40th Anniversary Native, Ti Native, Calendar Watu, Tanto PM2
Would like to own again: CQI Caribbean Sheepsfoot PE, Watu
Wishlist: Magnacut, Shaman Sprints!