A conversation with Gayle Bradley - PSF27

[Cliff Stamp]

In a YT video, Bradley made a comment about PSF27 regarding "grain size" and how it influenced carbide tearout. In particular, since it was spray formed but not HIP had a stronger resistance to carbide tearout. He then went on to say the reason why this happens was due to the shape/size of the carbides and the larger "grain" size.

A question was asked about this (on the forum) from a metallurgical perspective because a larger austenite grain size is strongly known (materials data) to reduce strength and toughness and as well (Landes work) apex stability directly. A bit of a concern in these discussions is what people mean by grain size because as me2 is fond of pointing out people often refer to both the size of the carbides and the size of the austenite as "grain size".

I called Mr. Bradley to ask him about this and we spoke for quite some time. We spoke about his experience with PSF27 vs ingot and HIP steels. How he sharpened them, how he sharpened in general and many other things. It was clear immediately that he wasn't making the argument that PSF27 resisted carbide tearout better because of the metallurgical reasoning he made in that video, but his evidence was that he saw it. The metallurgy was just an attempt to explain why it happens, not as an argument as to that it happens, two very different arguments.

As to the metallurgy, it is an interesting question/point and the first time I have heard an argument that not HIP'ing a steel would enhances its performance (as it is known to decrease porosity for example). Generally the reason that spray forming tries to avoid HIP is because it is expensive, hence the research into how to spray form to achieve a high density. I have asked a bunch of people in the field (who do that work) do they have any data and have been looking for it myself. No luck so far to support or deny Bradley's hypothesis.

The point of this post however was simply to note respect/admiration for someone who would actually answer questions and provide justification for his claims. At no point in the conversation was Bradley upset or even irritated that I didn't simply accept something because he said it and he actually was interested that I wanted to know why he asserted it, what was his evidence and he was happy to provide it and to share what he knew with someone who wanted to learn/understand.

As I can come across (shocking) as a bit critical of makers, I thought it only fair to note this kind of thing for which I hold in high regard. At the end he asked if I understood it or was I just confused and I ended with confusion is a good thing anyway because the minute you are not confused you are not trying to learn. The unknown is always confusing, if it wasn't then it would be the known. I will be picking up one of the Bradley PSF27 collaborations for no other reason than to support that behavior as if you don't support what you argue should be done it is pointless to argue for it.

[ManixFan]

Steel and metallurgy aside........that is one beautiful example of a fixed blade Bowie that also has a nice ergonomic handle with some interesting handle options (i.e., the two tube pins) available for those who also might find themselves in a "survivor" situation and can use this style of handle to more easily lash the knife to a branch limb to function as a spear.

Personally, I think the knife has a very attractive aesthetic as well as being very functional in usage.
I will be picking one up for sure! :)

[Ankerson]

I have found PSF27 to be an interesting steel, more aggressive than CPM D2 while a little less aggressive than standard D2, that's been my own observations anyway.

So that supports IMO what Mr. Bradly was talking about on the video and the larger grain size that he was referring to over CPM D2.

I have no reason to doubt what Mr Bradly was talking about at all as it all made perfect sense to me when he was talking about it, in the way that he explained it.

I think it helped a lot that I had already worked with it a lot in the Mule Team before the video. :)

Still in the process of testing it, working with it etc, sitting on my desk currently as I type this.

I will admit when I 1st heard about the steel I wasn't all that excited about it really as I wasn't excited about CPM D2 when I tested it and standard D2 is very aggressive so I liked that.

So I was like, another powered D2?

Turning out to be better than I thought it was going to be. :cool:

[Cliff Stamp]

I have found PSF27 to be an interesting steel, more aggressive than CPM D2 while a little less aggressive than standard D2, that's been my own observations anyway.

It used to be argued fairly strongly that steel itself, due to its structure had "cutting ability", due to things like carbides or varying microstructures. One of the stronger proponents was David Boye who went as far to argue that rolling steel lowered this cutting ability and hence he preferred to work with cast steel where the dendretic structure was retained. This kind of argument is severely outdated.

Comparisons by Swaim in the late 90's showed that the cutting ability of knives was due to things like the edge angle and finish, not the steel itself. Mike showed that even simple steels with no carbide volume, if sharpened at a lower angle and coarse grit finish would easily out slice something like D2 which has a very coarse austenite grain and very large primary aggregate.

It is even noted in the actual literature as Verhoeven for example compared the cutting ability of damascus blades which were also argued to have this kind of aggression/cutting ability and found again, same as Mike, that the cutting ability is geometry and finish orientated, not due to the steel due to carbides or any other inhomogeneity. As he worked with actual knife makers, it is rare to see anyone still make that argument, even the people who make the knives because the data is clear.

If you move beyond Verhoeven and look at the materials data on actual cutting mechanics then it is even more clear because cutting is controlled by things like the rupture pressure, friction, fracture mechanics, etc. and these are in the equations as functions of the geometry and surface finish. The equations can model the data perfectly fine without any factor for some kind of steel inhomogeneity.

--

Now as an aside, if you let knives get really dull, and you are slicing, then you get an odd kind of behavior where the sharpness can actually increase as you do cutting. This can be seen on CATRA graphs for example if you look at the raw data. This happens because as the edge blunts it does so in an uneven manner and it produces a jagged surface. This jagged nature can at random produce a kind of micro-serration and thus push the cutting ability up a little, but it has to again be remembered this is a low sharpness. There is a similar effect often exploited in industry by fusing dissimilar metals and using the faster rate of wear of one to provide a kind of cutting edge. But in knives, this doesn't work well, unless again you are looking for very low sharpness. An example of that is the carbidized edge put on Titanium blades, Keffeler has been experimenting with this on steels even as have others. It might be useful on machetes and other blades which are used in very dull/damaged conditions.

[Cliff Stamp]

I have found PSF27 to be an interesting steel, more aggressive than CPM D2 while a little less aggressive than standard D2, that's been my own observations anyway.

[...]

So that supports IMO what Mr. Bradly was talking about on the video and the larger grain size that he was referring to over CPM D2.

That has nothing to do with Bradley's comment about increased apex stability which he also noted was not in between standard/wrought steels and HIP steels, he noted he found it was superior to both that was the point of interest. The difference in the carbide size is well known as spray forming is not knew, what is new is how to adjust the process to achieve high density so as to avoid HIP. For details on the carbide/grain size see for example T15 in standard, spray form and HIP in C. Spiegelhauer's work.

The interesting part then is how you could have some kind of discontinuity where a carbide size inbetween wrought and PM steels produces a higher apex stability, especially when it is known that the bulk strength in standard bend fracture tests for example shows what you would expect, that the strength is right inbetween both. Bradley argues it is due to the nature of the grain/carbides, their shape, that might be possible but I have not seen any data on it and in C. Spiegelhauer's work the carbides look to be the same shape in spray and HIP processes and I don't see how they would be different. But again, that doesn't mean they could not be.

[opusxpn]

I like the steel psf27 got the mules it is very similar as far as sharpening and cutting ability as my queen D2 folding knife but the PSF27 I think I can push it to a lower angle and still get a good edge. I will also be getting Mr. Bradley's bowie

[Cliff Stamp]

I like the steel psf27 got the mules it is very similar as far as sharpening and cutting ability as my queen D2 folding knife but the PSF27 I think I can push it to a lower angle and still get a good edge.

Have you used CPM-D2, or any CPM steel like S30V, CPM 154 ?

[Ankerson]

I have found PSF27 to be an interesting steel, more aggressive than CPM D2 while a little less aggressive than standard D2, that's been my own observations anyway.

[...]

So that supports IMO what Mr. Bradly was talking about on the video and the larger grain size that he was referring to over CPM D2.

That has nothing to do with Bradley's comment about increased apex stability which he also noted was not in between standard/wrought steels and HIP steels, he noted he found it was superior to both that was the point of interest. The difference in the carbide size is well known as spray forming is not knew, what is new is how to adjust the process to achieve high density so as to avoid HIP. For details on the carbide/grain size see for example T15 in standard, spray form and HIP in C. Spiegelhauer's work.

The interesting part then is how you could have some kind of discontinuity where a carbide size inbetween wrought and PM steels produces a higher apex stability, especially when it is known that the bulk strength in standard bend fracture tests for example shows what you would expect, that the strength is right inbetween both. Bradley argues it is due to the nature of the grain/carbides, their shape, that might be possible but I have not seen any data on it and in C. Spiegelhauer's work the carbides look to be the same shape in spray and HIP processes and I don't see how they would be different. But again, that doesn't mean they could not be.

All I know for sure is what I have experienced personally.

Other than that I will take Mr Bradly's word for the rest until I see something different.

As we see more of it around I am sure we will see more feedback overall on the steel, some of the other Custom Guys seem to like it also.

[Bodog]

I've been using the **** out of my PSF27 MT. It's very, very good. After normal tasks like cutting up mucho cardboard, busting pallet straps, and hacking at wood, the initial bevel from the factory showed no signs of chipping or rolling. I was very impressed, I couldn't do that with many other steels, mostly they all chip or roll. So I decided to take it down to a much lower angle. I dropped it to 8 degrees per side and cutting regular cardboard caused a fairly extreme amount of chipping. I created a relief bevel set at about 12 degrees per side and it was still a little too low; for normal tasks it's fine but any kind of rough cutting sees immediate fracturing and a breaking of the edge. I wouldn't even call it chipping, large sections just break off. Not deep, mind you, just long. So I raised the relief bevel more. It's at about 14 degrees per side and it's pretty much back to what I would consider impressive performance. When I say rough cutting, I'm talking about things like slipping the blade under tight pallet straps and twisting the edge up, causing a lot of lateral loading. I also cut a lot of rough, dirty cardboard. There's no controls there, some is really dirty and thin, some is clean but thick. The edge performs very well at a modest 28 degree inclusive relief bevel but I thinned the actual stock too much when I went down to 8 dps.

Compared to S110v which, at least what I had from another company at high thickness with an edge at about 20 dps, the S110V chipped very easily even after removing the factory edge. S30v is very good and I'd say the cutting performance between S30v and PSF27 is comparable while the toughness of PSF27 is higher. I bent the blade far enough for it to set at about 25 degrees. That was created by slow loading and the actual bend itself started approximately 1.5 inches from the tip with a slow continuous bend until reaching the tip. I slipped almost the entire blade under a flat piece of heavy glass, lifted the glass, and held it there for a minute or two. Since it didn't break (which honestly surprised me) I took a hammer to it and straightened it out and then finessed it back by prying it in the opposite direction. I couldn't do that with the S30v steel, I've seen it snap easily with much lower angled and much less stressful prying. So if it comes to legitimate knife work like separating ribs or joints or whatever, PSF27 can handle what S30V can't. For reference, the other ingot D2 I've played with I kept at around 20 dps to get the same edge stability and that blade was thicker, too.

I've needed to awl into wood which the knife has done without issue. I've needed to bust open crates on the fly without appropriate tools so I've used an ASP baton and batoned the knife through wood. No issues. The only other knives I'd really try that with are the higher toughness carbon steels or blades with very thick stock. I've seen many, many other steels snap in half doing these things but to be fair, the other knives I've seen snap are either lower quality knives or knives simply not designed to do such things because of steel that's not adequately tough or not thick enough. This one is relatively thin, keeps a good edge, is definitely adequately corrosion resistant, and takes a pretty dang good beating. I'm sure if I just clamped it in a vice and beat on it with a sledgehammer I could break it but I have yet to really ever need to do anything like that with a knife so I think that's an unreasonable testing method. I've been hard on it and it's done fine. I'd think the Bradley Bowie will be a beast of a knife. Money is tight right now or I'd absolutely buy one.

I live close to the atlantic ocean and work literally feet away from it and sometimes go out on to the water to do my job. My blade goes every time. With, literally, the most minimal care the exposed blade doesn't rust or stain. I've let it set overnight with mustard with no stains or rust forming compared to a slight patina forming with the same mustard on 1095 in about 10 minutes. I get rained on quite often. I carry my blade in a kydex sheath. I do not dry the knife after getting dumped on. No rust. When I initially received the knife I left it uncoated and just slapped the handles on it. Within a month a light layer of rust had formed underneath the handles, so I sanded the rust off (metal remained slightly stained), heated the blade, threw some froglube on it, put the handles back on, and since then, no more rust under the handles.

If you guys want to see a few pictures, do a search for the MT19 here. I've been using it since and it really is one of the best all around steels that I've used. I'm no steel guru, but I've used probably 10 to 15 different steels from various companies in various configurations. In my opinion, whatever that may be worth to anyone, I'd rather carry PSF27 than S110V, B75P, 154CM, Elmax, etc. I've not used 3V or Cruwear so I can't comment, though I wish I had those steels. I think that 4V will meet or exceed PSF27 but that's just hypothetical right now because the only stuff out there is either custom made with small batch heat treats (which is kind of unfair to compare) or they come in stupid stock thicknesses if you can find it at all.

[tvenuto]

I've held off on the MT19 because I plan on picking up the bradley bowie. Your post makes me consider snagging both.

[MacLaren]

I've held off on the MT19 because I plan on picking up the bradley bowie. Your post makes me consider snagging both.

It certainly does :)

[Cliff Stamp]

Compared to S110v which, at least what I had from another company at high thickness with an edge at about 20 dps, the S110V chipped very easily even after removing the factory edge. S30v is very good and I'd say the cutting performance between S30v and PSF27 is comparable while the toughness of PSF27 is higher.



[...]

So if it comes to legitimate knife work like separating ribs or joints or whatever, PSF27 can handle what S30V can't. For reference, the other ingot D2 I've played with I kept at around 20 dps to get the same edge stability and that blade was thicker, too.

[...]
I'd rather carry PSF27 than S110V, B75P, 154CM, Elmax, etc.

Thanks for the details, all of that corresponds well to the material properties of those steels and is easy to understand on that basis.

I would be really curious as to you perspective on PSF27 vs PM D2, 3V PM 154CM, RWL34 or similar steels if you do get a chance to use them.

[Bugout Bill]

Bodog: A lot of high carbide steels can take a pretty dramatic set.

[opusxpn]

I like the steel psf27 got the mules it is very similar as far as sharpening and cutting ability as my queen D2 folding knife but the PSF27 I think I can push it to a lower angle and still get a good edge.

Have you used CPM-D2, or any CPM steel like S30V, CPM 154 ?

Yes sir I have s30v

[Cliff Stamp]

... I have s30v

How do you find it compares to PSF27?

[Ankerson]

I've been using the **** out of my PSF27 MT. It's very, very good. After normal tasks like cutting up mucho cardboard, busting pallet straps, and hacking at wood, the initial bevel from the factory showed no signs of chipping or rolling. I was very impressed, I couldn't do that with many other steels, mostly they all chip or roll. So I decided to take it down to a much lower angle. I dropped it to 8 degrees per side and cutting regular cardboard caused a fairly extreme amount of chipping. I created a relief bevel set at about 12 degrees per side and it was still a little too low; for normal tasks it's fine but any kind of rough cutting sees immediate fracturing and a breaking of the edge. I wouldn't even call it chipping, large sections just break off. Not deep, mind you, just long. So I raised the relief bevel more. It's at about 14 degrees per side and it's pretty much back to what I would consider impressive performance. When I say rough cutting, I'm talking about things like slipping the blade under tight pallet straps and twisting the edge up, causing a lot of lateral loading. I also cut a lot of rough, dirty cardboard. There's no controls there, some is really dirty and thin, some is clean but thick. The edge performs very well at a modest 28 degree inclusive relief bevel but I thinned the actual stock too much when I went down to 8 dps.

Compared to S110v which, at least what I had from another company at high thickness with an edge at about 20 dps, the S110V chipped very easily even after removing the factory edge. S30v is very good and I'd say the cutting performance between S30v and PSF27 is comparable while the toughness of PSF27 is higher. I bent the blade far enough for it to set at about 25 degrees. That was created by slow loading and the actual bend itself started approximately 1.5 inches from the tip with a slow continuous bend until reaching the tip. I slipped almost the entire blade under a flat piece of heavy glass, lifted the glass, and held it there for a minute or two. Since it didn't break (which honestly surprised me) I took a hammer to it and straightened it out and then finessed it back by prying it in the opposite direction. I couldn't do that with the S30v steel, I've seen it snap easily with much lower angled and much less stressful prying. So if it comes to legitimate knife work like separating ribs or joints or whatever, PSF27 can handle what S30V can't. For reference, the other ingot D2 I've played with I kept at around 20 dps to get the same edge stability and that blade was thicker, too.

I've needed to awl into wood which the knife has done without issue. I've needed to bust open crates on the fly without appropriate tools so I've used an ASP baton and batoned the knife through wood. No issues. The only other knives I'd really try that with are the higher toughness carbon steels or blades with very thick stock. I've seen many, many other steels snap in half doing these things but to be fair, the other knives I've seen snap are either lower quality knives or knives simply not designed to do such things because of steel that's not adequately tough or not thick enough. This one is relatively thin, keeps a good edge, is definitely adequately corrosion resistant, and takes a pretty dang good beating. I'm sure if I just clamped it in a vice and beat on it with a sledgehammer I could break it but I have yet to really ever need to do anything like that with a knife so I think that's an unreasonable testing method. I've been hard on it and it's done fine. I'd think the Bradley Bowie will be a beast of a knife. Money is tight right now or I'd absolutely buy one.

I live close to the atlantic ocean and work literally feet away from it and sometimes go out on to the water to do my job. My blade goes every time. With, literally, the most minimal care the exposed blade doesn't rust or stain. I've let it set overnight with mustard with no stains or rust forming compared to a slight patina forming with the same mustard on 1095 in about 10 minutes. I get rained on quite often. I carry my blade in a kydex sheath. I do not dry the knife after getting dumped on. No rust. When I initially received the knife I left it uncoated and just slapped the handles on it. Within a month a light layer of rust had formed underneath the handles, so I sanded the rust off (metal remained slightly stained), heated the blade, threw some froglube on it, put the handles back on, and since then, no more rust under the handles.

If you guys want to see a few pictures, do a search for the MT19 here. I've been using it since and it really is one of the best all around steels that I've used. I'm no steel guru, but I've used probably 10 to 15 different steels from various companies in various configurations. In my opinion, whatever that may be worth to anyone, I'd rather carry PSF27 than S110V, B75P, 154CM, Elmax, etc. I've not used 3V or Cruwear so I can't comment, though I wish I had those steels. I think that 4V will meet or exceed PSF27 but that's just hypothetical right now because the only stuff out there is either custom made with small batch heat treats (which is kind of unfair to compare) or they come in stupid stock thicknesses if you can find it at all.

Thanks. :)

Very nice overview, I was waiting for you to write something on it as I know you have been using the heck out of that Mule team. :cool:

[KevinOubre]

I have found PSF27 to be an interesting steel, more aggressive than CPM D2 while a little less aggressive than standard D2, that's been my own observations anyway.

It used to be argued fairly strongly that steel itself, due to its structure had "cutting ability", due to things like carbides or varying microstructures. One of the stronger proponents was David Boye who went as far to argue that rolling steel lowered this cutting ability and hence he preferred to work with cast steel where the dendretic structure was retained. This kind of argument is severely outdated.

Comparisons by Swaim in the late 90's showed that the cutting ability of knives was due to things like the edge angle and finish, not the steel itself. Mike showed that even simple steels with no carbide volume, if sharpened at a lower angle and coarse grit finish would easily out slice something like D2 which has a very coarse austenite grain and very large primary aggregate.

It is even noted in the actual literature as Verhoeven for example compared the cutting ability of damascus blades which were also argued to have this kind of aggression/cutting ability and found again, same as Mike, that the cutting ability is geometry and finish orientated, not due to the steel due to carbides or any other inhomogeneity. As he worked with actual knife makers, it is rare to see anyone still make that argument, even the people who make the knives because the data is clear.

If you move beyond Verhoeven and look at the materials data on actual cutting mechanics then it is even more clear because cutting is controlled by things like the rupture pressure, friction, fracture mechanics, etc. and these are in the equations as functions of the geometry and surface finish. The equations can model the data perfectly fine without any factor for some kind of steel inhomogeneity.

--

Now as an aside, if you let knives get really dull, and you are slicing, then you get an odd kind of behavior where the sharpness can actually increase as you do cutting. This can be seen on CATRA graphs for example if you look at the raw data. This happens because as the edge blunts it does so in an uneven manner and it produces a jagged surface. This jagged nature can at random produce a kind of micro-serration and thus push the cutting ability up a little, but it has to again be remembered this is a low sharpness. There is a similar effect often exploited in industry by fusing dissimilar metals and using the faster rate of wear of one to provide a kind of cutting edge. But in knives, this doesn't work well, unless again you are looking for very low sharpness. An example of that is the carbidized edge put on Titanium blades, Keffeler has been experimenting with this on steels even as have others. It might be useful on machetes and other blades which are used in very dull/damaged conditions.

Cliff, based on these conclusions from Swain and Landes, what then is the purpose of different steels in knives? If what they show and what some of your experiments have shown is that steel isn't that important, then what is the point of using anything other than 1084 and 420HC? How do we account for the dramatic edge retention accounts from numerous people in the industry regarding steels like S110V, ZDP-189, M4, etc? They are used and recommended by very credible makers that you yourself admire such as R. J. Martin and Sal Glesser. Has the whole industry taken a wrong turn with their testing protocols? Do you think the relatively thick edge preferences of most people account for the performance of higher carbide steels verses the simpler steels? This is something I have been thinking about for some times since getting to know you and your work and looking up the work of many of the individuals you cite. Even my own anecdotal evidence has yielded different results often times than what you and others find in regards to steels.

[Bodog]

Compared to S110v which, at least what I had from another company at high thickness with an edge at about 20 dps, the S110V chipped very easily even after removing the factory edge. S30v is very good and I'd say the cutting performance between S30v and PSF27 is comparable while the toughness of PSF27 is higher.



[...]

So if it comes to legitimate knife work like separating ribs or joints or whatever, PSF27 can handle what S30V can't. For reference, the other ingot D2 I've played with I kept at around 20 dps to get the same edge stability and that blade was thicker, too.

[...]
I'd rather carry PSF27 than S110V, B75P, 154CM, Elmax, etc.

Thanks for the details, all of that corresponds well to the material properties of those steels and is easy to understand on that basis.

I would be really curious as to you perspective on PSF27 vs PM D2, 3V PM 154CM, RWL34 or similar steels if you do get a chance to use them.

Absolutely. That's what the mule team is there for. If I can manage to scrape up to the funds when these blades drop, I'm going to jump. I'm definitely in with Maxamet and 4V if/when they drop, though my hopes of Maxamet as all around steel are pretty low. I'm pretty curious about RWL34 though it's not extremely pressing. CPMD2 is probably not going to happen unless it's released as a Mule blade. Same with 3V, but Chris Berry has a knife he's about to drop in 3V that's extremely enticing. 60-61 rc ground to .010 - .015". That's interesting. Here in a couple of days I'll find out if I have the funds required to drop on a test blade (it's pretty expensive) that has the real likelihood of breaking. I already know I don't need a supremely thinly ground knife.

[Bodog]

I've been using the **** out of my PSF27 MT. It's very, very good. After normal tasks like cutting up mucho cardboard, busting pallet straps, and hacking at wood, the initial bevel from the factory showed no signs of chipping or rolling. I was very impressed, I couldn't do that with many other steels, mostly they all chip or roll. So I decided to take it down to a much lower angle. I dropped it to 8 degrees per side and cutting regular cardboard caused a fairly extreme amount of chipping. I created a relief bevel set at about 12 degrees per side and it was still a little too low; for normal tasks it's fine but any kind of rough cutting sees immediate fracturing and a breaking of the edge. I wouldn't even call it chipping, large sections just break off. Not deep, mind you, just long. So I raised the relief bevel more. It's at about 14 degrees per side and it's pretty much back to what I would consider impressive performance. When I say rough cutting, I'm talking about things like slipping the blade under tight pallet straps and twisting the edge up, causing a lot of lateral loading. I also cut a lot of rough, dirty cardboard. There's no controls there, some is really dirty and thin, some is clean but thick. The edge performs very well at a modest 28 degree inclusive relief bevel but I thinned the actual stock too much when I went down to 8 dps.

Compared to S110v which, at least what I had from another company at high thickness with an edge at about 20 dps, the S110V chipped very easily even after removing the factory edge. S30v is very good and I'd say the cutting performance between S30v and PSF27 is comparable while the toughness of PSF27 is higher. I bent the blade far enough for it to set at about 25 degrees. That was created by slow loading and the actual bend itself started approximately 1.5 inches from the tip with a slow continuous bend until reaching the tip. I slipped almost the entire blade under a flat piece of heavy glass, lifted the glass, and held it there for a minute or two. Since it didn't break (which honestly surprised me) I took a hammer to it and straightened it out and then finessed it back by prying it in the opposite direction. I couldn't do that with the S30v steel, I've seen it snap easily with much lower angled and much less stressful prying. So if it comes to legitimate knife work like separating ribs or joints or whatever, PSF27 can handle what S30V can't. For reference, the other ingot D2 I've played with I kept at around 20 dps to get the same edge stability and that blade was thicker, too.

I've needed to awl into wood which the knife has done without issue. I've needed to bust open crates on the fly without appropriate tools so I've used an ASP baton and batoned the knife through wood. No issues. The only other knives I'd really try that with are the higher toughness carbon steels or blades with very thick stock. I've seen many, many other steels snap in half doing these things but to be fair, the other knives I've seen snap are either lower quality knives or knives simply not designed to do such things because of steel that's not adequately tough or not thick enough. This one is relatively thin, keeps a good edge, is definitely adequately corrosion resistant, and takes a pretty dang good beating. I'm sure if I just clamped it in a vice and beat on it with a sledgehammer I could break it but I have yet to really ever need to do anything like that with a knife so I think that's an unreasonable testing method. I've been hard on it and it's done fine. I'd think the Bradley Bowie will be a beast of a knife. Money is tight right now or I'd absolutely buy one.

I live close to the atlantic ocean and work literally feet away from it and sometimes go out on to the water to do my job. My blade goes every time. With, literally, the most minimal care the exposed blade doesn't rust or stain. I've let it set overnight with mustard with no stains or rust forming compared to a slight patina forming with the same mustard on 1095 in about 10 minutes. I get rained on quite often. I carry my blade in a kydex sheath. I do not dry the knife after getting dumped on. No rust. When I initially received the knife I left it uncoated and just slapped the handles on it. Within a month a light layer of rust had formed underneath the handles, so I sanded the rust off (metal remained slightly stained), heated the blade, threw some froglube on it, put the handles back on, and since then, no more rust under the handles.

If you guys want to see a few pictures, do a search for the MT19 here. I've been using it since and it really is one of the best all around steels that I've used. I'm no steel guru, but I've used probably 10 to 15 different steels from various companies in various configurations. In my opinion, whatever that may be worth to anyone, I'd rather carry PSF27 than S110V, B75P, 154CM, Elmax, etc. I've not used 3V or Cruwear so I can't comment, though I wish I had those steels. I think that 4V will meet or exceed PSF27 but that's just hypothetical right now because the only stuff out there is either custom made with small batch heat treats (which is kind of unfair to compare) or they come in stupid stock thicknesses if you can find it at all.

Thanks. :)

Very nice overview, I was waiting for you to write something on it as I know you have been using the heck out of that Mule team. :cool:

And I look forward to your reviews as well.

[tvenuto]

Cliff, based on these conclusions from Swain and Landes, what then is the purpose of different steels in knives? If what they show and what some of your experiments have shown is that steel isn't that important, then what is the point of using anything other than 1084 and 420HC? How do we account for the dramatic edge retention accounts from numerous people in the industry regarding steels like S110V, ZDP-189, M4, etc? They are used and recommended by very credible makers that you yourself admire such as R. J. Martin and Sal Glesser. Has the whole industry taken a wrong turn with their testing protocols? Do you think the relatively thick edge preferences of most people account for the performance of higher carbide steels verses the simpler steels? This is something I have been thinking about for some times since getting to know you and your work and looking up the work of many of the individuals you cite. Even my own anecdotal evidence has yielded different results often times than what you and others find in regards to steels.

I'm sure Cliff will reply but I have an analogy that you may find helpful. Take two baseball stadiums that have their own unique layout. Because of this, one of them is harder to hit home runs in than the other. On the same night, two games are played, one in each stadium. 3 home runs are hit in Stadium A, and 5 in Stadium B. Which one was harder to hit home runs in? The answer is: we probably still don't know. There are many other factors that would influence how many home runs are hit in those stadiums in a single game: batter skill, pitcher skill, game situation, etc. Not only that, but those factors are actually more important than the shape of the stadium. Now this doesn't change the fact that one of these stadiums really is harder to hit home runs in, however, the issue is what it takes to show that one is harder. It takes many games with many different batters and pitchers and game situations for these things to normalize out. So with knives, the steels you listed really do have different properties, and one of them will really perform better given a certain geometry/use/finish grit etc. However, it's very difficult to show this, because you'd need to test all of those different geometries/uses/finish grits many times to normalize out the other factors that contribute to the scatter in the data you collect to tease out the actual effect of the steel itself (just like the stadium itself). In the case of finish grit, Cliff is attempting to do just that, but it is one factor of many.