HAP40 upgrade?

[Bloke]

The way I understand it, there's no way to hrc test a cladded metal, like hap40/sus410.
If that's the case, it can be listed at any hardness without backing it up.

Hey J, I’m not too sure this is accurate. The reason being I can’t help but think that any outer cladding could be easily and accurately ground away both sides on a surface grinder to expose a clean and parallel core steel to test hardness. :)

Anyhow, I’m all for hard and tough rusty blade steels particularly in a Military.

I don't know anything about hrc testing, but would the amount of uncladded HAP 40 seen here on my Stretch for example not be enough for that? Look how high the "cladding line" is up the blade...

Hey Gernot, it may well be enough steel to test. I'm not too familiar with the testing process and figured a parallel strip of steel rather than a wedge may be optimal, but I'm only guessing. :)

[jpm2]

The way I understand it, there's no way to hrc test a cladded metal, like hap40/sus410.
If that's the case, it can be listed at any hardness without backing it up.

Hey J, I’m not too sure this is accurate. The reason being I can’t help but think that any outer cladding could be easily and accurately ground away both sides on a surface grinder to expose a clean and parallel core steel to test hardness. :)

Anyhow, I’m all for hard and tough rusty blade steels particularly in a Military.

I don't know anything about hrc testing, but would the amount of uncladded HAP 40 seen here on my Stretch for example not be enough for that? Look how high the "cladding line" is up the blade...

Hey Gernot, it may well be enough steel to test. I'm not too familiar with the testing process and figured a parallel strip of steel rather than a wedge may be optimal, but I'm only guessing. :)

In addition to the parallel/flat piece (like the tang), I think there's a minimum size and thickness. Not sure if after milling the clad away on both sides, there'd be enough thickness left?

[awa54]

I'm guessing that the issue with hardness testing on laminate blades is more that it can't be done without damaging or even destroying the test sample (someone's beloved Sprint Spydie!).

If Manufacturers didn't play so coy with hardness numbers (which they undoubtedly already know as part of production QC measurements) then testing a completed blade after the fact and the quandary that presents wouldn't be required...

[Cambertree]

Somebody else commented in another thread that cladded HAP40 is limited in HRC due to the cladding. Made sense to me.

I'll buy any 3.7" or longer Seki non-cladded, higher HRC40 Spydie made in the future :) Endura or Police would be superb !

I have seen cladded HAP40 kitchen knives listed as 65-66.

Interesting. I wonder what the stainless cladding was? Could be it's a different steel to SUS410?

Sal did say somewhere that optimum heat treat for laminated steels with regard to folding knife needs, has to take into account the response of both the core and cladding steels.

I would think if the Seki maker can produce and heat treat K390, then they should be able to do a harder, monometal HAP40.

Here's a question for you all though: we all like playing with cool steels no doubt, but do people who actually use clad HAP40 in everyday work feel like it's failing any kind of edge retention yardstick?

Or is it just a conceptual 'inferiority' to the REX45 knives?

I've got a bunch of HAP40 Spydies I use as working knives, and I don't have any issues with them. If running it as it is gives higher toughness and ease of resharpening to a razor edge, then I'm not too fussed about it being a few HRC points less than REX45.

But I don't have a REX45 knife to compare it to. All high wear resistance steels still lose that super fine edge apex about as quickly as any other steels in my experience. I do touch up sharpening or stropping at least every couple of days during hard use at work, if not every day. So theoretical edge retention doesn't really matter that much to me, except as it bears an influence on edge behaviour at high sharpness levels.

I'd be interested to hear from people who've used both clad HAP40 and REX45.

[Baron Mind]

Somebody else commented in another thread that cladded HAP40 is limited in HRC due to the cladding. Made sense to me.

I'll buy any 3.7" or longer Seki non-cladded, higher HRC40 Spydie made in the future :) Endura or Police would be superb !

I have seen cladded HAP40 kitchen knives listed as 65-66.

Interesting. I wonder what the stainless cladding was? Could be it's a different steel to SUS410?

Sal did say somewhere that optimum heat treat for laminated steels with regard to folding knife needs, has to take into account the response of both the core and cladding steels.

I would think if the Seki maker can produce and heat treat K390, then they should be able to do a harder, monometal HAP40.

Here's a question for you all though: we all like playing with cool steels no doubt, but do people who actually use clad HAP40 in everyday work feel like it's failing any kind of edge retention yardstick?

Or is it just a conceptual 'inferiority' to the REX45 knives?

I've got a bunch of HAP40 Spydies I use as working knives, and I don't have any issues with them. If running it as it is gives higher toughness and ease of resharpening to a razor edge, then I'm not too fussed about it being a few HRC points less than REX45.

But I don't have a REX45 knife to compare it to. All high wear resistance steels still lose that super fine edge apex about as quickly as any other steels in my experience. I do touch up sharpening or stropping at least every couple of days during hard use at work, if not every day. So theoretical edge retention doesn't really matter that much to me, except as it bears an influence on edge behaviour at high sharpness levels.

I'd be interested to hear from people who've used both clad HAP40 and REX45.

https://youtu.be/FPrKByImasY

[Cambertree]

https://youtu.be/FPrKByImasY

Thanks BM. Christy does excellent work. I'd seen that video a while ago, but it was good to rewatch it in the context of this thread.

20% more cardboard cut before losing hair whittling sharpness, does seem like a worthwhile performance increase, doesn't it?

What impressed me more is that the REX45 still carried that high, hair whittling sharpness after both the cardboard slicing and the pinewood carving.

Kinda reminded me why I got all excited about HAP40 in the first place - the ability to hold onto that high sharpness a bit better than some of the other common high carbide steels.

Any other comments from anyone about how REX45 performs in everyday use? When the edge starts to deteriorate, does it dull by slow wear or rolling, like HAP40, or does it start developing microchipping at the apex?

I would expect corrosion resistance to be reduced at higher hardness too. Is there any noticeable difference between the two steels?

I'm curious what other changes we might expect if monometal HAP40 blades were run up to the 64-66 HRc range?

[Albatross]

https://youtu.be/FPrKByImasY

Thanks BM. Christy does excellent work. I'd seen that video a while ago, but it was good to rewatch it in the context of this thread.

20% more cardboard cut before losing hair whittling sharpness, does seem like a worthwhile performance increase, doesn't it?

What impressed me more is that the REX45 still carried that high, hair whittling sharpness after both the cardboard slicing and the pinewood carving.

Kinda reminded me why I got all excited about HAP40 in the first place - the ability to hold onto that high sharpness a bit better than some of the other common high carbide steels.

Any other comments from anyone about how REX45 performs in everyday use? When the edge starts to deteriorate, does it dull by slow wear or rolling, like HAP40, or does it start developing microchipping at the apex?

I would expect corrosion resistance to be reduced at higher hardness too. Is there any noticeable difference between the two steels?

I'm curious what other changes we might expect if monometal HAP40 blades were run up to the 64-66 HRc range?

If I'm not mistaken, Rex pulls even further away from Hap40 when the working edge is factored in as well.

I haven't experienced any micro chipping on my Rex45 Military, the edge is very stable. I did have some minor corrosion on my Rex blade, but still nothing on my Hap40(on the exposed, non-laminated portion that is).

[Cambertree]

If I'm not mistaken, Rex pulls even further away from Hap40 when the working edge is factored in as well.

I haven't experienced any micro chipping on my Rex45 Military, the edge is very stable. I did have some minor corrosion on my Rex blade, but still nothing on my Hap40(on the exposed, non-laminated portion that is).

Thanks. A couple more questions for you or anyone else, if you don't mind.

How do you like the sharpening response of REX45 vs. the Seki HAP40?

Big Brown Bear has shown that the toughness still seems to be very good for the rougher end of EDC type tasks. Does anyone have any comments on how REX45 holds up over time based on their own EDC usage?

One of the reasons I like HAP40 so much, is I'm not necessarily wanting it to be the be-all and end-all of wear resistance, but it has all the qualities which I like in a simple carbon steel like 1095, or steels like 01 and Superblue, but it just seems a bit better in nearly all aspects for my use.

It sharpens to a hairsplitting edge very easily, it seems to hold that high sharpness quite well, it's able to get a good sharpening response on a variety of abrasives, it's a bit more corrosion resistant, and it tends toward rolling rather than chipping, when pushed beyond its normal limits. It's still plenty tough, too.

If REX45/HAP40 retains those characteristics at 64-66 HRC then it sounds like a must-have CQI improvement.

[HerbToker]

Somebody else commented in another thread that cladded HAP40 is limited in HRC due to the cladding. Made sense to me.

I'll buy any 3.7" or longer Seki non-cladded, higher HRC40 Spydie made in the future :) Endura or Police would be superb !

I have seen cladded HAP40 kitchen knives listed as 65-66.

Sukenari does their HAP40 at 68hrc, still durable enough too, ~9 thou 9 ish dps.

[The Mastiff]

Here's a question for you all though: we all like playing with cool steels no doubt, but do people who actually use clad HAP40 in everyday work feel like it's failing any kind of edge retention yardstick?

Or is it just a conceptual 'inferiority' to the REX45 knives?

IMO, yes. In my use it's a likeable steel that performs well and sharpens nicely. As a user it's a very good steel. Was there some performance left out? Not enough for me to worry about. If I need higher wear steels I use them. If I need tougher I select one. More corrosion resistant? In theory I guess I could but rarely do as I don't mind maintenance and can carry blued carbon steel here in the summer with firearms and in comparison almost all knives are super easy so I rarely select just for that.

I used to argue the reason for demanding highest hardness's and thinnest edges from my knives but I've gotten away from that. Mostly from practical reasons because I have had and still do have customs ran to the nth degree and I see the impracticality of it for a factory made knife. As I state if I need more of something I just go to the box and get it. HAP 40 can be run harder I suppose but I like it exactly as it is. I very rarely ask for the hardest numbers I can get even on customs.

[kwakster]

Well, i have no experience with Spyderco models in cladded HAP40 steel, only with sharpening/polishing several Japanese Kohetsu santoku's & gyuto's in cladded HAP40 @ 65 HRC for both a few demanding amateur and pro-Chefs, and based on feedback those knives are actually my current king of the hill regarding taking and holding highly polished edges (up to 1.0 micron diamond compound), maybe even a bit better than ZDP-189, but much less sensitive to edge corrosion, as well as seemingly tougher overall.
Chipping doesn't seem to happen easily for such hard knives, and when they do those chips tend to be noticeably smaller compared to ZDP-189 steel of the same hardness.

Started this picture thread some time ago about a few of those Kohetsu HAP40 santoku's here:
https://www.bladeforums.com/threads/koh ... u.1509214/