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Ran into this question on a forum I read occasionally.
"What makes a good knife?"
Any thoughts?
"What makes a good knife?"
Any thoughts?
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Depends on intended function.
Has to cut, or chop, or slice, or poke, or whatever.
Has to keep on cutting, or chopping, or slicing, or poking, or whatever-ing.
Has to have an edge and hold an edge.
Has to be usable wihtout fatigue.
Has to provide firm grip even in slipery environs.
Lazy folk would prefer low maintennace, but I think stainless steel sucks. (Just a personal opinion.)
Being good looking in addition to hard working is a big plus - why stop at halfway? -
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Stainless steel is very good..... butter knives, wall decorations, belt decoartions... will confess to keeping a lil stanless generic folder in my fly vest, but it gets soaked every few days and used rarely and I am lazy about some things.
When I first read the question, what came to mind was if the knife does what it supose to do relably and the owner is happy with it, everything else is value judgement and personal prefernce. Then I thought aboput it some more... came to the conclusion that the only requirement for a good knife is the satisfation it delivers to the owner. I have some knowledge about what is going on with knives, therefore have become more finicky about it. The clever in my kitchen is thicker and harder than the "chef knife" I cut most things with. The later see a steel often, the prior sees a stone rarely. If I didn't know what I know. I'd probably be happy with semi-disposable stainless cutlery, like most people who don't know there is a chioce -
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There are some good stainless steel knives out there - differently heat treated, hard cutting edge, etc. They tend to be made out of the more unusual alloys and none are mass produced - so they are hard to find.
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If I am not mistaken all species of stainless are cryo-teated because there isn't enough carbon in them to actually harden (in the sence that an HC steel hardens). Cold processing isn't a bad thing, is used for some components is race motors. I won't use a salt tank for my 52100, so I am sure as hell not going to risk the nastiness that can happen as you pour acetone over crushed dry ice to cryo-treat a blade. Exotic stainless alloys... you can forge titanium too, or T1 with a tack hammer, for that matter you can forge obsidean and cool it in a glass blower's annealing oven so it doesn't self destruct with a to short cooling time, but why? What's the avalability of these exotic strainless alloys? The cost? The practicality to the average bladesmith?
Funky stainless blades might make the best option for a pro marine diver or something, but if they were a viable material, probably more smiths would be using them. Makes me wonder why every top quality chef's knife I have ever seen or heard of is made from some variation of HC steel. The culinary arts aren't know for thier lack of flambouency.1095 hasn't been around forver, basically the metal the industrial revolution was built with, and 52100 hasn't been the standard steel bearing material since GM developed it over 100 years ago, because there are more viable options.
Stainless blades have a reason and or purpose, but they are of no use to me personally. I'll believe there is an actual "good" stainless blade when I handle one, and that will probably be the day before I bring my car to the shop to have the wheel bearings (52100) replaced with milled synthetic safires (If the connect seems odd, look into the developement of 52100).
If someone can find a reason for charging more for something, they will find a way to market it. In the cycle of bigger-better-more-faster-now, there does reach an extreme where the ... ummmm ... consumer is easily parted with thier money. -
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Some stainless steel alloys have more than enough carbon to heat treat - many in fact are air hardening, like D2. But these alloys are hard to work - most don't deform easily when heated but that is what they where designed for. Truthfully they really aren't knife steels although some will use them for it. What makes these steels hard is not primarily cementite (iron cardide), but other cardides (WC, Cr3C2, VC, Mn2C, etc). Because these steels are so very hard, they are probably best used in pattern welding with a softer and tougher steel to form a composite that balances the properties to make a good knife. I'm thinking of try to make a double edged rapier out of D2/L6 pattern welded steel - hard cutting edge with enough springness not to snap without the difficulties of differently tempering the edge vs center of the blade (an engineered design for a good blade). Will it work? Only one way to find out.
BTW: There is no nastiness in pouring acetone or IPA over dry ice - just a little messy if you pour to fast. -
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If you are billeting steels, you may want to match up steel which move about equally under the hammer, either a higher carbon with a slightly lower carbon, of a high carbon and an alloy which moves similarly. If the solution hardend steel (alloy) moves much more slowly than the the other steel it is pair with, during the drawing out processes, it will cause an un-uniform pattern to develope by letting the freer flowing steel to squish around, usually out the edges. In the more extreme cases what you end up with after many Tap in the edges / re-welding / drawing processes is the more free flowing steel encapsulating the less fluid steel - a lot of time and work to put a rod inside a larger rod. After defroming and etching the expected pattern may not be found, or may be found as groups of tight bands separated by larger sections of only the freer flowing steel. Is an interesting effect though. Remeber after the 3rd or 4th welding heat most of the carbon will have migrated to a more homgonious dispertion, leaving only the solution hardened aspects of the alloy(ies) to yield different qualities.
"Truthfully they really aren't knife steels although some will use them for it." * if someone can find a reason to charge more for something, they will find a way to market it (and created and imagened need for it as well).
Exotic, purpose specific alloying, general blade smithing... next are the minutia of where stainless begins and ends vs the other highly alloyed types of steel begin and end going to be dredged up out of the peripheria? Its red... no its orange........ and the are both grey in black in white. -
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Your point is one that I have thought about and it is a serious concern in trying what I'm thinking about.
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Rapiers have a good amount of flex and a wierd tip if I remeber correctly from the fencing class I was tossed out of in college. You may want to stay with the very-tried-and-very-true combination of 1095 and 15N20 (givertake 1075 with a good amount of nickle), especialy if it is you first big pattern welding project, or your first big blade project. The reason I suggest this is that they weld very easily, move equaly under the hammer, similar critical temps and the like while still giving a good pattern developement and layer counts even below 50. An added bonus is that if you run into troble with the balance between flex and hardness and tempering, it shouldn't be too hard to find someone who has done what you are trying to accomplish with that combination of steels. No reason to reinvent the wheel sometimes, though most of us try it more often than we need to.
Was thinking a rapier with a tight twist and lower layer count would probably look preety cool - candy cane meets leathality. Thought about it a bit more and if you bring the finished billet out to a slightly thicker and shorter version of the bar you'll need to work the blade from and put a "pinapple twist" into the billet rod as part of the deformation steps, you might be able to get a pattern which would not only show the layers, but the almost overlapping dimond shapes of the "pineapple twist" will probably end up looking like scales when pounded flat as the rod is elongated to its final length and width.
Think I just figured out what is going to happen to those two 10.9 bolts my jetta offerd up to me and the lawn mower blade that showed up on my hood the other day. Should be able to get 3 pieces each out of the bolts 1/2 x thin x not so long. pound out / hot cut the mower blade to match up to it and do a pinned billet of 12 layers. Draw out as thin and narrow as possible / hot cut into 6ths / repin re-weld / 72 layers / square rod short and stout / pineapple it and see if I can get a scaled pattern on a early willow leaf shaped seax.
Anyhow, good luck with the project.
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You've piqued my interest, Troy... when you say "differently heat treated," do you mean "differentially heat treated?" If so, I would love to see an example. If you mean "heat treated differently than HC," then, well, yeah. Verhoeven's article goes into why: mse.iastate.edu/files/verhoeven/7-5.pdf
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Ah a typo, I meant "differentially heat treated."
"If so, I would love to see an example." Do you mean of any differentially heat treated blade or a differentially heat
treated double edge blade or allowing a blade made with something like D2 to air harden as I was alluding to?
To differentially heat treated blade one heats the spine (side away from the edge) of the blade with a torch until the desired temper color appears. But I think you already know about that. One could also clay coat the blade prior to hardening, like the Japanese followed by a cool (~300 F) temper of the edge.
To differentially heat treat a double edge blade one could clay coat the blade (see above). Or one could try to temper the blade by carefully heating along the centerline of the blade, but that would be very difficult with a blade as narrow as most rapiers. -
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There are always tempering tongs, or in this case of a long, thin, double edged blade a well heated round would work, so long as you kept flipping the blade regularly to get even exposre to the tempering heat, and the slower selective temper rate would allow for better control than a torch.
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That would work but with an 1 - 1.5 inch wide blade even that would be very difficult. Come-on, heating the center to 450-550 F while the edges are, tops, 350 F - possible but hard to do. Most rapiers aren't tempered this like what we are talking about, instead only the first 3-6 inches are left hard while rest is temper to spring steel (deep blue).
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Perhaps I misunderstood. I thougth you meant "differentially hardened air-hardening steel." That's something I've not yet seen in a blade.
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Differentially hardening air hardening steel is possible but neither of us has the equipment to do it (vacuum ovens with microwave heaters (truthfully, masers) etc). Then again what's the point, air hardening steels aren't normally used for knives.
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Have selectively tempered many double-edged daggers, athames et al in this manner, with out any problems - some less the ¾” wide, thin-bladed, with a flat geometry nearly approaching a modern fillet knife. Is simply a matter of the contact surface and how much heat the heated rod holds. For the sake of convinence, I have modified to round to a somewhat pyramid shape with the ‘point’ flattened to 1/8th down the length of the rod, but that wasn’t really necessary, just worth the effort for the convinence of letting the blade balance on the flat surface. When the length isn’t an issue, I leave the heated rod on the fire within the forge. Have another round with a ¼” slot pounded in down its length the selectively temper single edged blades the same way, by balancing the flat spine in the ¼” slot (usually with the rod sitting on the fire within the forge). The process works well and has for a very long time. Not as though I invented it. Is simply a matter of the tools matching the size of the piece being worked.
Rapiers are a long, flexible puncturing tool, mostly flexible with a hard, small chisel tip to maximize force (puncturing ability) at the point of contact. If the edges are sharp at all, they are a secondary consideration. They are not intended for a side to side slicing action, More often, they are left thickish and rounded over to add strength when deflecting an incoming rapier.
It’s not as though an intermittent, vertical quench technique could be used, keeping the front 1/8 or so of the blade submerged in the quenchant for maximizing hardness while the rest of the blade receives less quench time as you progress to the rearward end of the blade. It’s not as though you can feathering the hardness by constantly submerging and withdrawing the blade into and out of the quenchant while keeping the tip submerged and get a progressive and selective hardness up the length of the blade. It’s not as though you can temper the entire blade slightly and then temper the tip again on the edge of basically a well heated 3-corner file. It’s not as though this process has ever been used before… is not complicated enough.
Most knives, or rapiers are made out of exotic stainless alloys for the price of the specialized equipment and difficulties envolved. There comes a point where worth outweighs value, but then again, if an imagined need is created… the umm… customer and his money are soon parted.
Back to the original point: The satisfaction derived by the user defines the goodness of the knife. Everything thing else is value judgment, theory, hairs to be split or hypothetical special case senerio, air hardening, exotic alloy or not.
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Funny... everyone went off on a tangent.
To me, a good knife is a good tool...
feels good in my hand
keeps a good edge
could be thrown if needed without worrying that it might be lost or broken
My favorite knife... is a little dirk I picked up at a flea market for $5 that satisfies all the above listed criteria. I keep it in my hands, flipping it around, when I watch medieval movies (In case they need my help) Is it my best knife, no, it is my most expensive knife, no, is it a good knife... DAMN SKIPPY.
