The Cutting Edge, a discussin' of blade design

Since we're starting to drown in spam, I thought I'd start this thread.
Man has used sharp things since he came down out of the trees. The
origins are lost in the backwaters of Time. It's a toss-up whether the edge came first, or the hammer, but between them, we have gone to the Moon over the last 12,000 odd years of development. It is the purpose of this discussin' to look at that development with an eye to the How and Why of blade design and fabrication. Jump right in, don't be shy, tell us what you Really Think.
Charly
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Down with metals!!! All you really need is a hard rock and an antler to produce REAL sharp edges.
Pete Stanaitis ----------------------
Charly the Bastard wrote:

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Pete & sheri wrote:

Well, I agree with your second statement, but I suspect that you'll have a sharp-enough edge with much less work if you use metal.
This is probably why we almost always use metals for edges instead of stone.
So I'm forced to disagree with your first statement.
--

Tim Wescott
Wescott Design Services
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I hold a very unpopular view where it comes to knives. I don't like ultra-hard knives.
I like simple carbon steels like 1095 and 5160, and low alloy stain resistant steels.
I have a buddy who doesn't take a knife seriously unless it is made from A6 or D2, or worse yet CPM440V.
I have never understood this fascination with knives you can carve glass with.
The ultimate steel to me is what Henckel uses for their kitchen knives.
X45CrMoV15 (0.45% carbon - 0.15% Vanadium)
It is similar to a 420SS but with more vanadium.
I like it because it is easy to work, holds a decent edge, is easy to sharpen and resists rust just enough.
Now if I could just find a supplier in the US to buy some.
BTW if anybody is interested, these are the steels used by some other big kitchen knife makers.
Whusthof-Trident X50CrMoV15 Sabatier X55CrMoV15
I just don't understand why these steels aren't available off the shelf.
Of course my other oddness is making bronze knives from Phosphor Bronze. It is strictly a cold process. Cut your blank from sheet and start hammering edge down until it gets cold worked so much it starts to chip. Then clean up and sharpen with a fine hand file.
Strop the edge on your jeans and you can shave the hair off your arm. No joke. From making bronze knives I learned why ancient bronze kvies and swords, never have points. They can't. Points go away very fast after only a few sharpenings of a bronze knife. It is all slicing, not piercing.
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Was that the sound of a can of worms being opened? :)

I'm the same, hold unpopular veiws, but because I do-like extra hard knife blades. The ones you mentioned aren't hard enough for me. ;)
A6, D2, 440C are soft weak junk to me. :/ Sorry. :/

5160. Ick. ;)
1095 is ok if it's cold treated and drawn to at least ~66hrc. Better is 50100-B which is also W7 and like 6195. The best I know of so far is M2 at ~64hrc.
Ok, so most of the knives I use are the 56-58 hrc production knives but still the extra hard ones have their place. After getting used to one and what they'll cut, the others seem brain dead. Not talking about crap like 440C, D2 and other Cr diluted, soft-ass stuff but good knife blades like a Case with their chrome-vanadium steel (50100-B, BTW;) are ok for most stuff but plain ol' can't do certain cuts.
I'm not sure if I still have the picture I scanned of a pile of flashing I cut off with a homemade 1095 blade. The story is, I cut computer cases down to make lead molds using a skilsaw and an 1/8"x 7+1/4" AlOx wheel. I cut the flashing off about 16 linear feet of cuts with a 1" long 1095 knife blade without resharpening it. Some of the cuts required more than one pass, the flashing was so stinking thick in places.
I've had my extra hard blades tested for edge holding by butchers and ranchers and a carpet layer. D2 440C etc can't do what mine will do.

The steels you mentioned A6, D2, 440C aren't all that hard... just wear resistant.
A2 for instance, has A6 and/or D2 whipped in hardness -and- strength!
A2 is also stronger than O1.
Why O1 is so weak is because it's Mn based just like A6 is. :/ A2 and O7 are Cr based and much stronger than A6/D2 and O1. A2 has about as much Cr in it as is benificial... any more and the Cr starts to weaken and soften the steel. Stainless steels have sometimes triple A2's amount. :/
But Stainless steel has other problems relating to corrosion resistance being paramount in it's formulation. Like too much Cu and Si. Funny how Cu is hardly aver mentioned in a stainless steel's composition isn't it? ;)
Tool steel is .25% maximum except for the W series then it's .20% Cu max. In practice it's much less than that.
Stainless steel is understood to be .35% to .65% Cu unless otherwise stated... for corrosion resistance and only for corrosion resistance.

We have a stainless Wustoff knife, my girl friend wanted it. :/ It doesn't hold an edge worth a damn, compared to say, and old Robeson that I picked up at the second hand store and re-shape and sharpened. The Robeson was chrome plate over 50100-B, btw. ;)

Since I actually prefer the tarnish on old knives, stainless steel with all it's weaknesses is crap, IMO. ;)
I looked and looked and finally found some truely straight high carbon steel hacksaw blades. They sparked tested like 1095, made in china. I drew the temper on some of them to 475F for one hour. Then I cut some angle iron for use as braces to test, the harder ones cut a full 4 times as much steel as the softer ones.
My 1095 and 50100-B knife are more like the hard ones. 475F was chosen since it brought the hardness down to the "knife industry's magic" 58hrc. :)
M2 HSS is hyped to hold an edge 7 times the carbon hacksaw blades. I don't know if it's 7 times but that's pretty close and a skinning knife made from a power hacksaw blade is the best to be had... that we've found so far.
We tested a heat and cold treated ATS-34 knife (Paul Bos) and found it to "be the best stainless steel knife ever" but... ;) "not nearly as good as a hard 1095 blade". This test was by butchering cattle out primary use of big knives.
A guy can like whatever he wants, but how in the heck is he supposed to know what's best if he's not even been given a "chance" to know? ...They don't make extra hard knives for you to test against. :/
If and only if corrosion resistance/looks is most important, stainless steel ain't the answer. ;)
A guy could also draw the temper on a file and see how it performs. ;)
The main thing you'd notice is "no edge integrity" the file just won't be able to cut into some of the stuff you are used to cutting with a file. File teeth are about 65-66 hrc.
I say, extra hard knife blades at 64hrc and higher have "a place" alondg with other knives... too bad most guys in this world will never know the joy. :(
Don't believe me. You guys are blacksmiths, try it for yourselves.
:-)
Alvin in AZ
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snipped-for-privacy@XX.com wrote:

All right, we have a winner! First criteria, hardness. How hard is hard enough? What part do alloying agents play in the final hardenability of the blade? If hardness is the goal, then why aren't there knives made of solid carbide, which if memory serves, is about a 90Rc. Certainly, TiN coated machine tooling lasts much longer than the HSS, but the carbides will slice this like a hot knife, even 'dull'. So is it really hardness or resistance to wear that's the Golden Fleece? What really does the work?
Charly
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Charly the Bastard wrote:
[...]

I dunno much about Jason's Rockwell Quest, but farriers' hoof knives might be a special case.
Farriers' knives encounter everything from tissue to rocks in use and hard knives get dull just as quickly as relatively soft knives. As I see it, the only difference is that hard knives are damned difficult to sharpen.
Personally, I use a chainsaw file between horses to maintain a saw edge on my knives (What heresy!) and look upon hoof knives as consumables, not works of art. Needless to say, my opinion is not shared by my knifemaker friends, who make beautiful hoof knives with pattern welded blades and fancy handles, but I tell 'em I'm in the farrier business, not the art gallery business. (g)
--
Tom Stovall, CJF
Farrier & Blacksmith
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On Fri, 30 Jul 2004 22:44:26 +0000 (UTC), snipped-for-privacy@XX.com wrote:

I also make knives as a hobby, I was working as a machinist for a tool maufacturing company for many years, whenever I gave someone one of my knives I always reminded them that "The company I worked for made very good pry bars,, I don't,, use this knife for cutting and it will most likely outlive you, with very little maintainence,, use it as a prybar and you may be picking pieces of it out of your hide."
Bear
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Cool! You are the only other knife maker I know that's into making them as hard as posible. :)
Which steels do you use?
My knives come with a lifetime gaurantee- "if you don't treat it like it's made of glass, I guarantee you'll break it ;)"
Alvin in AZ
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On Sat, 31 Jul 2004 21:03:46 +0000 (UTC), snipped-for-privacy@XX.com wrote:

I use a lot of 52100 (old bearing races) Also some A2 I picked up from a scrap metal dealer, and a few old files, those out of files I slow grind with my fingertips of my guiding hand as close to the edge as I can so as to make certain they stay file hard, never letting the blade change color at all. When I was working for the tool company I was able to have a handfull of blades controlled atmosphere heat treated (read no scale at all) to the exact hardness I wanted for a cup of coffee or a can of pop,, God how I miss that place,,,
The softer blades do have their place, but there are plenty of good ones of that type comercially available already, for very reasonable prices, therefore no real need for anyone to custom make them. The exception would be fillet knives, all of the ones I have used were either too hard to flex properly or so soft they dulled too fast and gummed up my diamond hone when I was sharpening them. quite by accident I found out that the backing steel of a Lennox bi-metal bandsaw blade (13 foot by 1 1/4 by .047) worked great as is as long as I ground it slow enough as to not affect the temper, only drawback being the need for a solid carbide drill bit in a very solid machine (like a Bridgeport vertical mill at the least) to drill the holes for the handle pins, even the toolroom drill press had too much slop in the spindle and the corners chipped away on the bits, even cobalt drill bits in the Bridgeport just melted down when tried using them,, even with a heavy mist coolant system running on them. Bear
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The smaller stuff is 50100 but you prob'ly knew that already. And the really;) big ones can be carbon-cased 8660, you prob'ly knew that already too huh? ;)

Ebay?
Oh man. :) Tried that and didn't have the patience for it. :/ Did you use a belt grinder to do that?
Ever see a "torsional toughness test graph" for 1095? Shows the strength of the steel peaks, when drawn for an hour, at 325 to 350F. (350 to 375F for O1)
To get max hardness I put my freshly quenched blades (not the springs) in the freezer for an hour or so at -5F before any tempering draw. Then put them in boiling water for 1/2 hour which brings them up to higher than quenched hardness. (little known fact;) Then put them back into the freezer for another shock to un-stabilize any more austenite that will decompose. Then finally the 1 hour draw at 350F.
The extra hardness obtained by the boiling water draw prob'ly doesn't help a dangged thing, but I need to clean off the oil and boiling them is a good way to quickly change their temperature to kick the retained austenite around maybe getting more of to decompose. ;)
Anyway, theortically the 1095 and 50100-B blades are a good solid 65-66hrc, about the same as file teeth. :)
But most of my re-heat treated files are having "crumbly edge" trouble! :/ So I'm not recommending my process for files at this time. ;)
When it does work on files it works great tho! ;)

Alloys I'd really like to have are O7 and F2 (or F3) that I could heat treat myself, but I've also always wanted to make a "tough knife" from A2 also. I can't heat treat that stuff like I figure it needs to be. Also IMO it really needs to be, before any tempering, brought down to at least -120F. So I've set myself up all these hurdles to make a knife from A2 that I may never jump. :/ If me and my son get into the metallurgy class this fall, that's one thing I'm hoping for, a chance to heat -and- cold treat at least one A2 knife blade.
Oh yeah and I have some VascoWear around here too. ;) It's not exactly, but very similar to A7.
The other thing I'm hoping for is to finally figure out why I'm having trouble with crumbly edges on most of my re-heat-treated (factory heat treated first) files and 1095 knives.
Theoretically the second heat treatment could be better than the first because of further grain refinement. Ain't working out that way, most of the time, tho. ;)

Ontario Brand "Old Hickory" or Russell Green River blades come to mind. :) Cheap as dirt. Only about double my price just for the steel. ;)

We need to figure out some sort of trade so I could get some of that. :)
I have some single-metal band saw blade that's .054", not sure if it's worth a hoot or not just yet. First worth-while knife is in the works right now, so not tested yet.
I've lately been having pretty good luck drilling the power hacksaw blades with carbide-tile-bits from home depot and reaming to size with an 1/8" carbide-burr. That works good with my .122" nails I've been using for pins lately. ;)
Plain and simple as I can make them. :) To me GOOD tools are "found in their using", not in their fancy looks. :)
Alvin in AZ
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On Sun, 1 Aug 2004 22:41:28 +0000 (UTC), snipped-for-privacy@XX.com wrote:

I kinda thought that was the situation on one with an 8 in ID,, totally different spark pattern, and it ground too easy after cooling, I didn't know the exact steel, only that it was way softer than what I had been using in the 3 to 6 in ID range

no, local, Ibought that before Ebay existed,, and right now down to only enough for 2 more blades,, I wish I could find a truckload at the price I picked that up for,, 125 pounds at $0.20 / pound, all 3/8 in flatstock

Yep, a 3 inch by 10 foot belt grinder with 60 grit belt running at 105 MPH ,, I don't remember what it is in SF/S,, but I had figured it down to MPH one time for my Dad so he could get his head around what my fingers were playing so close to,, it scared the crap out of him.
It doesn't take near as much patience as it does to carve jewelry pieces from mussel shell with only needle files and emery cloth,, and I've been known to do that too. ;o)

Most likely, but was so long ago that I don't remember it at all, I read my way through about a 4 foot shelf full of books on melalurgy, about half dealing with nothing but the sciences involved in heat treating of various steels back in the late 80s/early 90s

are you going straight back to critical temp then quenching? Anything I remember recommends annealling or at least normallising first. But then again the engineers I talked with that specialised in the heat treat area all said that heat treating any steel is more of an artform than an exact science.

A2 is some amazing stuff, I gave my Mom a hunting knife made of A2 for Christmas a few years back, the next deer season Dad was using it to skin out the buck Mom got,, the next morning he called me up all worried and asked if I could bring over my sharpening tools as he had a bit of an accident with Mom's knife,, when I got there he took me out to the garage and told me what happened, the hide was pretty stiff as the temps were close to zero and when he was cutting through the last part he stumbled and rammed the knife edge first into the concrete, he showed me where it hit, a groove about 1/16 inch deep by 1 1/2 inch long,, then we went inside and he showed me the knife,, yes, there was a chip in the edge of the blade,,but I needed a magnifying glass to see it, 4 or 5 passes on the diamond hone and it was good as new again.
As to working out a trade on the band saw blade material, I'll have to check on how much I have left. Bear
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Heard about them and read about them (in an SAE book) never actually ground on one yet. :/

Cool way to figure it. :) Brand new 10" grind stone's outer surface at 1800rpm is 53.5 mph. Which is what I use for hollow grinding.

I tried normalizing etc... maybe my metallurgy class teacher can help me figure it out since we'll be polishing and etching etc.
It's prob'ly just me and my sloppy heat treating methods. :/

Cool story, heard about A2 knives in other stories like that. :)
That crazy A2 stuff can get 2+1/2 to 3 points HRC harder with a -120F cold treatment -with no change in toughness- so it can be drawn and still be 65hrc. 65hrc and stronger than 62hrc O1... somhow just feel a need to make a "tough" knife like that. ;)

Wouldn't want it any other way. ;)
Alvin in AZ
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Brings to mind something I read in Weygers' book about using a nail as a drill bit to purposely heat up the place where you want to drill on treated steel before going to the actual drill bit. Obviously this is to take the hardness out of the steel at the spot you want to drill without drastically affecting the hardenss of the rest of the blade.
GA
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Good idea, but success depends on which steel. :)
For an extreme example... M2 HSS, drawn down to 45hrc using 1200F, takes 40 to 50 hours. ;) (40 hours when quenched from 2175F) (50 hours when quenched from 2225F) (ASM's Tool Steels 4th edition by Roberts and Cary)
What's funny about that to me is... -how chemistry-wise, HSS is still just iron and some other stuff. -and T1 HSS, developed before 1910, is still being used.
I have a few brand-new power hacksaw blades around here that are T1. All the rest are M2. Spark testing against a known sample is a real clincher in this case. :)
Alvin in AZ
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treated
the
drastically
Don't suppose it would do much good in that case...: /
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On Sat, 31 Jul 2004 22:38:17 +0000, bear wrote:

Lurker chiming in here...didn't I read here (or rec.metalwork) that you can chuck something flat-faced in the DP and draw the temper from just the spot you want to drill?
--
"Keep your ass behind you"


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So ya can! but as pointed out by our buddy from AZ, it's not much good on high speed steel... Should work great on more garden varieties though. Havn't tried it yet myself.
GA
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Can I back off on that at this time? ;)

I'll check it out later, I'll have make a point of booting into windows with my rig. ;)

Sounds hard for sure. :) Why were they useless? Broke? Too hard to sharpen?

Sounds like a need for a bi-metal blade.
Funny thing about hard steel tho, it can break, and even tho it didn't break until it got a much higher pressure on it than the one that bent and stayed bent... the broken one is thought of as weaker.

An HSS edged bi-metal blade could be sharpened on a bench grinder with no loss of hardness. Would that help any?

The cowboy's I know use their pocket knives while shoeing their horses sometimes. Believe it? ;)

For some odd reason, never really paid much attention to hoof knives, for sure, no one ever complained about them and drew my attention to them.
You prob'ly know as well as I do how "cowboys" do things, right? ;)
Alvin in AZ
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snipped-for-privacy@XX.com wrote:
re: Hoof knives
[deletia]

Too brittle, too hard to sharpen.

Soft and tough works for me. (g)

We farriers tend to use our tools pretty hard: Since a hoof knife is a pull tool, a blade is usually better bent than broken.

I don't know, I equate hard with brittle.

Sure I believe it. I've nailed on horseshoes with a 2# rounding hammer - it's the wrong tool for job, but it beats the hell out of using a rock. (g)

There are some beautiful, semi-custom, pricey, knives on the market that are forged from from esoteric steels, heat/cryogenic treated, and fitted with fancy exotic wood handles. Most of 'em are harder than the proverbial preacher's pee pee, chip/break at the slightest encounter with a rock or nail, difficult/impossible to sharpen quickly in the field - and as useless as teats on a boar hog for daily use.
I can get a good, usable, knife for less than $20, customize the hook with an angle grinder, keep it sharp with a chainsaw file, and it'll last me two or three months.

I've been off the sendero a time or two, but I ain't a pimple on a working cowboy's butt. I was about 14 when I figured out that rodeoing paid a helluva lot better and the work wasn't near as hard.
--
Tom Stovall, CJF
Farrier & Blacksmith
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