More work with the tension bar knife on wood :
The knife was used to cut down four Alders about two inches thick. On the first couple I attempted to just chop them down, this was not functional. It would take a hundred chops to get the stick weakened to the point where it could be jumped on or broken by bending / twisting. This was a massive amount of work compared to a decent sized knife or hatchet which would take this wood down in 1-2 cuts at maximum. The last two sticks were cut by bending the wood by hand and chopping into the region under the most stress. This peeled back the layers of wood readily and the last stick was cut with 25 hits, 10 were misses as it was a lot of ingrowth, plus my hand was getting tore up from the jagged end so my grip was not overly tight.
This isn't enough wood to build a shelter, about double the amount of sticks would be needed for just the top and back side, however considering how inefficient the first two sticks were cut, using the technique developed at the end, esaily eight sticks could have been cut with the knife with the same amount of chops, so the knife had the potential to cut down enough wood. The sticks were from 7-9 feet in length, and had 2-3 major branches from 0.5 to 0.75 inch thick, solid ones which could be used to frame out the sides. Many smaller branches could then be used to weave in the gaps. The sticks were fully limbed out, and even on the last stick the blade was still sharp enough to pop off the small branches, 1/16" thick.
After the chopping, the blade still had the abilitity to cut the heads off of grass stalks with a wrist pop. Later that night it was used to cut paper and tape for packaging, just a few pieces of each. It was steeled, but this made little difference, five passes per side on a fine ceramic rod and it was back to smoothly shaving sharp again.
Work with the tension bar knife on cardboard :
The cardboard was 1/8" thick, ridged, it was cut with a full slice over the three inch blade, sharpened with a fine ceramic rod to a shaving finish. The cuts were made until the blade was unable to cut the cardboard without tearing it. The knife cut six meters of cardboard before being so dulled. It was then steeled, and it could cut another meter before it would rip the cardboad again. It was again steeled and another meter of cardboard cut. The knife was then brought back to a fine shaving finish with three passes per side on a fine ceramic rod.
Jeff, I don't think it is actually hardenable, but it would be interesting to try. This was a piece off a tension bars removed from a fence that was torn down. It is very soft, the same length for example is much easier to bend than a six inch common nail. It would have been more infomative if I have started with a piece of 1020 cold rolled (or whatever), but I never really intended this to be anything more than a diversion - it didn't go at all as I expected, the knife was a lot more functional. I have a piece sent out to be hardness tested.
thombrogan :
I expect a person who knows his or her chosen alloy inside and out to make a better knife than someone who just cranks out a knife with a 'steel is steel' or 'better steel makes a better knife' attitude.
It is a factor sure, but not the only one, and possibly not even the critical one.
What about if the other guy simply uses a more suitable steel. There is no amount of work for example that you can put into 52100 that will give it the wear resistance of even the most stock heat treatment of CPM-10V. Thus if wear resistance is critical to your knife needs you go with the CPM-10V.
Similar arguements can be made for corrosion resistance and impact toughness among others, these properties can change more than ten to one from one cutlery alloy to the next (impact toughness is about fifty to one at maximum, corrosion resistance even more, and wear resistance more than ten to one).
Does working with the knives in any way (heat treatment, steels, geometry, etc.) mean that the quality of the knives will be raised. Yes and will any R&D. The end goals are fairly critical however as are the limits of the base materials.
So what you're saying is that the primary factors would be geometry and the hardness and toughness imbued by the heat-treatment and that steel type is secondary because an indestructable, barely dullable steel is worthless as a knife if it's not shaped, sharpened, and hardened and tempered appropriately for what it will be used to cut.
In regards to cutting ability just geometry matters. The use of a better steel (and heat treatment) is to allow the crafting of a more optimal geometry, one that is thinner and more acute or to enable the knife to have a wider scope of work.
Unless you have power grinding equipment or are willing to invest hours of hand grinding, the edge geometry may make or break a knife, assuming of course that cutting ability is one of your critical requirements, if it isn't then your viewpoint could obviously be very different.
Note as well that for some tasks, even the lower grade steel can take pretty much the most optimal geometry. For example Phil Wilson uses AISI-420HC for his kitchen knives (~54 HRC) and grinds them the exact same way as his CPM-S90V (~62/63 HRC) knives. The edge geometry is ~0.005" thick in both cases, with similar sharpening angles.
In this case using a better alloy doesn't allow the creation of a more optimal cutting geometry as it is pretty much minimal in both cases. The knives are fully flat ground right to the edge, zero thickness, and a very slight secondary edge bevel is applied. The "lower grade" steel also has advantages in regards to ductility and toughness (plus being a lot cheaper).
Of course the CPM-S90V version would offer better edge retention and easier sharpening due to less floppy burr formation (assuming the edge doesn't chip). However Wilson is quite to point out that he generally recommends AISI-420 HC for kitchen knives as edge retention isn't that key when sharpening is so easily available, and they respond so well to steeling.
Now for some knives, which have a much higher strength and toughness requirement, the functional geometries would be very different. L6 and ATS-34 would have very different geometries for a heavy chopper. Since L6 is so much tougher and can thus take a higher hardness, it can be much thinner, especially at the edge and still resist damage.
As an aside, some people like Jeff Clark and Joe Talmadge have described various steels taking sharper edges, I have never found this to be the case and can get razor edges or very aggressive slicing ones on D2, ATS-34, etc. . Jeff and Joe however have higher standards for sharpness than I do, and are probably much better at sharpening, Jeff in particular as he actually did it as a job. I would argue for most people, edge geometry and steel suitability are much more critical to ease of sharpening, and final edge quality.
If these knives perform all of the tasks that wonder-steeled knives do, will you be selling any of these Rebar-acudas to the general public?
They don't, as noted the edge retention is lower, and the reduced tensile strength limits various applications. They are probably not even functional in decently thin stock, 1/8" may bend even on heavy whittling and maybe even light baton chopping, need to try that, though it would still hold up to rope cutting, foods and such obviously.
However if there is interest I will offer a few models, the base price is $500 US - NO SHEATH. $550 with tactical black coating (marker), shipping is $50 outside of NL, expect one month for the dog team to reach the coast, at which time it is carried by seals to the mainland. 75$ for airmail (Pelicans).
Jose :
Buying a knife designed for the uses you had in mind would probably make more sense than having to modify the edge geometry.
Yes, this is ideal. It assumes of course that either you or the maker know how to determine the optimal geometry or materials.
The experiments with 52100 Ed and his colleagues have done over the last few years is probably the main reason he's been able to modify his edge geometry to get such thin edges on his blades without weakening them.
You can find the same edge geometry on knives by David Boye in *cast stainless* steel, and even in cheap production knives like an Opinel. Once bone cutting is removed from the intended scope of work of the knife, there really is no limit to the edge geometry.
I have a D2 blade ground much thinner (no secondary edge bevel, edge is ~5 degrees per side, 3/32" stock). Alvin Johnson grinds knives that make the Pronghorns look like prybars, his knives are fully hollow ground on thin stock, and the blade are ~0.010" a quarter inch back from the edge, 64-66 HRC on various carbon and HSS.
Feth :
[D2]
How much better would it hold a edge then the mild steel even unheat treated?
With a full annealing, I would not expect a lot more as the D2 would be very soft as well, and hardness is one of the main factors in edge retention as noted in the above (the response to steeling), plus I don't think the wear resistance would be great in a spheroidized steel.
... of major cracking or shattering
It is near impossible to induce fracture in low alloy steels, and very soft steels in general. They will essentially just deform until they rip apart.
-Cliff
