The Cutting Edge, a discussin' of blade design

On Fri, 30 Jul 2004 22:44:26 +0000 (UTC), snipped-for-privacy@XX.com wrote:
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If it's strength that rules, I've been wondering if anyone out there has any experience working with MP35N. The advertised tensile strength on this stuff is incredible. Unfortunately, hardness only goes to about 50Rc according to the literature I've seen. Regardless, I think this alloy is worth a little more googling. Maybe some kind of surface treatment would work (nitride, carbide, hammering diamond grit into the surface, quenching in newt blood?)
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snipped-for-privacy@torchlake.com wrote:
Re: Hard/sharp cutting edges...
[deletia]

Might be a bit hard on the hammer face. (g)
--
Tom Stovall, CJF
Farrier & Blacksmith
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What is MP35N? 50 hrc is not much harder than the spring in the back of an old pocket knife let alone the blade.
For everyday (don't know better;) uses, what's out there is fine.
If you want the ultimate cutting edge for a certain task it'll involve you figureing out what the most acute edge the material you are using for a knife blade can handle under the conditions.
"conditions" involve the user, another user might find a need for a more obtuse edge angle. BTDT when I loaned my knife to another to skin a deer back in the 80's, haven't loaned it out since. ;)
So far, in my quest, I've found M2 high speed steel is the best at ~64hrc. I figure chrome-moly-nickel steel from non-HSS saw blades at the hardest it can be drawn to (at stength) might be second best. (still learning)
The reason hardness is so important is the ability of it to cut -into- other stuff. I swear if you haven't gotten used to an extra hard blade, you're used to a knife that dulls and you don't know it. Like the boiled frog that started out, alive, in a pan of cool water. ;)
You've learned what a knife blade can do and aren't surprised by it's dulling as soon as it does. You've learned to expect it and learned to live with it. Why would you torture yourself over something that seemingly you can't do anything about? You've learned to live with it. :) I used to be the same way.
After getting used to an extra hard blade made from strong steel (both can be had even if "common knowledge" sez otherwise;) then go back to the old familiar 55-58hrc stuff... you can't believe why anyone would put up with that crap, until you realize... they just haven't had a chance to learn yet. :)
So what do you think? :)
Alvin in AZ (never been much of a believer in common knowledge)
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This stuff would suck for a knife, thats all there is to it. :)                            Les                                                                                                                UNS    R30035                         Typical Composition    0.025 max. C, 0.15 max. Mn, 0.015 max. P, 0.01 max. S, 0.15 max. Si, 19.00-21.00 Cr, 33.00-37.00 Ni, 9.00-11.00 Mo, 1.00 max. Ti, 0.01 B, 1.00 max Fe, Bal Co                         Get the complete data sheet <http://cartech.ides.com/datasheet.aspx?i 2&e=3>                                      Description    Carpenter MP35N alloy is a nonmagnetic, nickel-cobalt-chromium-molybdenum alloy possessing a unique combination of ultrahigh tensile strength (up to 300 ksi [2068 MPa]), good ductility and toughness, and excellent corrosion resistance. In addition, this alloy displays exceptional resistance to sulfidation, high temperature oxidation, and hydrogen embrittlement. The unique properties of MP35N alloy are developed through work hardening, phase transformation and aging. If the alloy is used in the fully work hardened condition, service temperatures up to 750F (399C) are suggested.                                                              Applications    Because of its unique combination of properties, MP35N alloy has been used in a wide variety of applications. It has been used in fasteners, springs, nonmagnetic electrical components and instrument parts in medical, seawater, oil and gas well, and chemical and food processing environments.                                                              
Typical Room Temperature Tensile Properties    % Cold Reduction    Ultimate Tensile Strength    0.2% Yield Strength    % Elongation    % Reduction in Area    Hardness         WORK STRENGTHENED                             0    135 ksi (931 MPa)    60 ksi (414 MPa)    70    70    8 HRC         15    155 ksi (1069 MPa)    118 ksi (814 MPa)    41    70    29 HRC         25    170 ksi (1172 MPa)    150 ksi (1034 MPa)    28    65    34 HRC         35    194 ksi (1336 MPa)    154 ksi (1062 MPa)    22    67    42 HRC         45    228 ksi (1572 MPa)    189 ksi (1303 MPa)    17    62    47 HRC         55    265 ksi (1827 MPa)    205 ksi (1413 MPa)    12    50    47 HRC         65    280 ksi (1931 MPa)    235 ksi (1620 MPa)    11    49    50 HRC         WORK STRENGTHENED + AGED 1000 DEGREES F (538 C) 4 HRS., AIR COOLED                             0    135 ksi (931 MPa)    60 ksi (414 MPa)    68    77    7 HRC         15    158 ksi (1089 MPa)    125 ksi (862 MPa)    39    70    33 HRC         25    186 ksi (1282 MPa)    175 ksi (1207 MPa)    24    65    39 HRC         35    203 ksi (1400 MPa)    195 ksi (1344 MPa)    21    62    43 HRC         45    257 ksi (1772 MPa)    251 ksi (1731 MPa)    12    52    46 HRC         53    300 ksi (2068 MPa)    290 ksi (1999 MPa)    10    48    50 HRC    
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snipped-for-privacy@nowhere.net wrote:

Ah yes, a Cobalt mix. :) Suffers from the same problem, hard grit in a soft matrix, but even worse that stainless steel with its high Chromium percentage.
Alvin in AZ (you can have my share of it;) ps- thanx for the info, Les :)
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On Thu, 29 Jul 2004 20:50:07 GMT, Ernie Leimkuhler

So what you are saying is that you really like to spend more time sharpening dull knives than you spend using sharp knives?
I'm not thinking a good knife should be able to carve glass,, but is certainly should be able to carve mild steel
;o) Bear
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I guess if you do a lot of whittling of steel that should work well for you. I use knives for cutting wood, food, plastic, paper, cardboard, and leather. I have yet to be attacked by a steel drum, a 2x4, or a hanging piece of 1" rope. I take my kitchen knives to my knife grinder once every other year, just for a touch up on a 600 grit belt to reset the bevel.
I have no trouble maintaining any of my knives with a diamond steel and a honing steel.
I have one 8" Henkel chefs knife that I have had for 22 years, with no appreciable wear. I am kind to my knives.
My pocket knife is an Al Mar Talon with a combo blade. It does everything I need a knife to do, is lightweight and holds a very good edge.
My knives never have a chance to get dull. If they do I can sharpen them very quickly.
I fully admit that if your average day includes having to cut very abrasive things like deer hair or cable sheathing then a harder edge is a good thing. But for average use I find them to be overkill, and a pain to reshaprpen once they do get dull.
If more people actually knew HOW to sharpen knives it wouldn't be as necessary to have edges that last forever.
If you really want the ultimate edge, just go ceramic.
Kyocera makes some excellent and durable ceramic knives for utility and kitchen use.
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On Sat, 31 Jul 2004 00:08:10 GMT, Ernie Leimkuhler

I fully agree with you there, Whenever i go to visit anyone in my family they always ask me to bring my sharpening tools with. the worst ones to sharpen were those of the older of my 2 sisters, her now ex-husband had tried to sharpen them himself ,, and left them in so bad a shape that I had to take them home and regrind the whole blades to get them back to the point where they could be sharpened properly with a diamond bench stone and ceramic steel. He had ground the blades down to very close to a 90 degree included angle,, and probably took a good 50 to 60 years off their useful life.
When it comes right down to it I guess it's the machinist in me that says that different tasks require different tools, and with that in mind the task that tool is meant to perform would determine both the material for that tool and it's hardness. the hunting knives I've made have been made of A2, 52100, and a few were made from worn out files, all were hardened and tempered to at 62 Rockwell C minimum. The 52100 one I made for my brother field dressed and skun out a moose, 2 black bears and 3 white tail deer, and could still shave the hair off my arm. however all my fillet knives are all made from the backing material from Lennox bi-metal bandsaw blades( the band I use are 13 foot by 1 1/4 by .047). After grinding off the high speed steel teeth, I've no idea what the backing steel really is, all I know is it is a very abrasion resistive spring steel that is already at 54 to 56 Rockwell C, (the perfect trade off point for flexibility and edge retention IMHO). Those fillet knife blades are made by stock removal only, at as low temp as I can, so as to not heat the edge and screw up the temper.
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Cardboard basically has "dirt;)" in it, like paper has clay in it.

Problem is you haven't actually gotten to use a knife like me and Bear are talking about. :/
I don't want to turn you away from your knives you have, just put them in perspective with what's posible. The idea that A6, D2 and 440V are like what I mean by an "extra-hard blade" made me want to tell you there is more out there than that. Knives that'll out perform those in edge taking -and- edge holding... by a bunch. :)

Huh? :/
It's not about that entirely... that's a side benefit to an extra hard blade.
An extra hard blade will cut into stuff you wouldn't dare cut-into with a knife, now. You have no need to cut into iron? This -is- the blacksmithing newsgroup ain't it? ;)
But really, if you were to draw the temper on a new file at 475F for an hour (58-60hrc) and then use it you'd have the experience of knowing what it's like to switch back to soft-ordinary blades after getting used to the extra hard ones.
Because right away, you'd notice the softer file won't cut into things like it did before.
That's what the folks that have used really hard blades have learned when going back to a regular knife.
As simple as that, if you can't see it with all my telling you about it you'll just have to experience it yourself I guess. :) But the experience I'm reporting to you won't be obtained by a D2, A6 or 440V knife blade they just can't get hard enough and their grain is too coarse too.

That statement just may be the answer. :) Ceramic is just the opposite of what I'm trying to get across. :)
An extra hard blade made from steel that can handle a fine thin edge will cut like a dream. The best you can get on most stainless steel and more so, with the ceramic, is a rather obtuse edge.
"At its most basic a knife is a wedge."
What we've found is ~65hrc M2 HSS is the best stuff for making a very acute angled "wedge" that can handle tasks that no other steel can.
My ~65hrc M2 HSS skinning knife has a final edge angle (not the knife blade but just the final edge, ok?) of about 10 degree total, that's a 5 degree "sharpening angle" on both sides.
A straight razor's final edge angle is ~17 degrees, total, that's about an 8+1/2 sharpening angle.
I made that knife and a bunch of others just like it back in the early 80's. The ones that haven't been broken are still going, the wear is so slow on them.
Ok, so you don't want a knife like that, and you have no need for a knife like that, and you're happy with what you have. :)
But now at least, do you know, they exist and they work great? :)
Alvin in AZ
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I feel that maybe I have not experienced a blade such as you describe.
But then again I might have made one by accident.
I do have a 1095 drop-point fixed blade knife I made long ago that was my first hollow ground knife. The edge ended up so thin after polishing that I was worried about it chipping. I heat treated it in my normal manner, which at the time was mostly guesswork. It seemed to hold a great edge, but I didn't think anything of it at the time. One day while in a junk store I found a nice honing steel in excellent shape. When I went to try it on my 1095 blade I successfully shaved the grooves right off the side of the honing steel, with no damage to the knife. I still have that knife, and it does take a very thin hard edge that lasts a long time.
Since I was a neophyte at the time, I didn't kept good notes as to my heat treating so I don't really know how I did it.
I have always liked 1095 as a simple knife steel that is very forgiving. I have made maybe 300 knives in 24 years. I have ground a few blades from ATS-34 but have yet to heat treat them. They were a bitch to grind since ATS-34 eats abrasive belts like jelly beans. I have since switched to ceramic belts which last much longer on my burrking.
I don't make many knives nowadays. I did a few for groomsman's gifts for a friends wedding. I really shouldn't have sharpened them before presentation. 3 out of the 5 guys manged to cut themselves during the reception.
Some people really can't be trusted with truly SHARP knives.
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On Wed, 04 Aug 2004 09:36:44 GMT, Ernie Leimkuhler
that's an understatement. I sharpened up my aunts kitchen knives for her,, when I started I had to look hard at them to decide which side was the one to sharpen, both were round,, first thing she did was to cut herself and needed 3 stitches to close it
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It's funny how I actually have a couple of my cold chisels and the "dull blade" in my stockman pocket knives are at a more acute angle than most knife knuts and their stainless steel knives.
Sad but true. It's been an up hill battle but I've gained NG allies over the years. :)
Started with my "thin hard blade" crap :/ right from the start on NGs when my son's ISP first got rec.knives.

Sounds like you have. Maybe you didn't pursue it because you had no real need for it? My cowboy friends (almost all my friends are cowboys, I tend to rub everyone else the wrong way, the cowboys aren't so easily rubbed the wrong way by my bullshit:) are what pushed me in that direction.
Ear marking, ball sack cutting, cactus shaving (cactus needles are hard and strong, just pretend to shave them off, almost all of them will pull out instead), skinning for the fur trade back in the "old" days and of coarse- butchering.

Sharpening steels are only good for blunt + soft "cold chisel edged" knives.
You speak of rods (steel and diamond coated) do you have a fine, white ceramic rod?

No sweat, if you want to do it again there's information available. GA has a graph now. :) Fig.7-30 page 212 that shows the torsional impact toughness test results- draw 1095 at 325-350F for one hour.
The unnotched chary is for structural steel and is useless in "the hard steel field of many tool steel uses" -ASM's Tool Steels

For a test, Bob Engnath sent me an ATS-34 knife blade heat and cold treated by Paul Bos. The result was "best stainless steel knife we ever used" But. "Still not all that good compared to the hard 1095 knives" And the hard 1095 knives were easily bettered by the hard 50100-B (6195/W7) and O1 knives let alone the M2 HSS power hacksaw bladed knives.

I've found ATS-34 just the opposite of that. :/
Stainless steel has a "CrO2 crust" on it and that's it. The insides grind like butter in my experience. Bob Engnath said so too. He said O1 (high Mn) was tougher on his belts than ATS-34 or 440C.
Bob E grinding me a CPM 10V blade and was going to have it heat treated by Paul Bos for a edge holding test when he up and died on us. :(

Oh, a "rich guy" huh? ;)

When you do, which steels? Forge them too?

No friggin way! :/

Cool. :)

Funny how different the ranchers are in that respect.
They start working cattle with their own pocket knives in elementry school. I had a Case knife dealership (Frost took over and raised the minumum order so kicked me out) and gave away as presents 6347's and 6392's to -kids-. And they used them and took care of them and sharpened them themselves too.
The clip blade is the "sharp blade" out west(?) (instead of the spey blade) and is laid flat on the stone to thin and very slightly raised to put the final edge on. Nothing like seeing a little boy or girl covered with dust and blood, stopping to sharpen their "sharp blade" while working cattle. :)
Replacing their clip blade with a piece of hard M2 HSS or at least re-heat+cold treating their chrome-vanadium blade (50100-B;) is a real hit! ;) Believe it? ;)
Alvin in AZ
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At the time I was buying very cheap belts

I buy the economy ceramics. They are a mix of ceramic and aluminum oxide. I just buy 60 grits for medium roughing. I have 24 and 36 grit zirconiums for real hogging of steel.
I really need a bigger motor for my burrking. I have a model 760 that I converted from 2x60 to 2x72.

I still have some 1095 from a big order I placed many years ago. I also make craft knives from files. I liked W-1 but it is very hard to find anymore. I have some O-1 and some ATS-34 sitting around.

When I can. I don't have a smithy at my shop, but I can use the one at school where I teach welding. I used to forge almost completey to shape with only cosmetic grinding needed.
I have made a few pattern welded blades and a few cable damascus blades. Cable damascus blades are very easy and pretty, and if you get the right cable can end up as very high carbon content.
I decided a long time ago not to make my living as a knifemaker.
You can check out my web-gallery for pictures of some of my knives.
http://www.stagesmith.com /

Well they were sghian duhs and none of them were used to having a sharp knife in a sheath tucked into their socks.

I have brought so many knives back from an early grave.
My favorite kitchen knife is a huge 14" Trumpet Brand chefs knife from 1905. It has a lovely, wide, thin, high carbon blade that takes a wicked edge. I just keep it away from onions. I redid the handle in Bocote.
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Yeah! I'm on the same page with you there! I like big ugly utility (or "Using" as they say around the knife forum) knives for general purpose and throwing (playing with). Prefer fixed blades that I can beat up and I like to be able to put a quick edge on it when it gets dull. Hard sharp knives are application specific and you need to care for them like any precision tool. A "tough" fixed blade will serve for just about any task at hand and if it isn't sharp enough then you can put a new edge on it as needed without spending a lot of time at it. Just my preference... Been known to carry around a smallish hand ground fixed blade made of mild steel and no complaints.
GA

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On Thu, 29 Jul 2004 13:47:01 +0000, Charly the Bastard wrote:

OT, but relevant:
news.individual.net
is a free european (but open to anyone who registers) news server with good retention and good spam-filters. I barely see any spam on this group, or any other.
--
BigEgg


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