The most common reasons we see blades fail dramatically almost always boils down to one or a combination of three issues:
A)
Inherent flaws in the material, which no smith or grinder or heat-treater can entirely correct,
more commonly,
B)
Bad heat-treat, which usually means the steel was over-heated and the grain "blew up", making the whole piece much weaker,
and most common of all,
C)
Inappropriate design/geometry for the intended use, which usually means either blatant stress risers at points of leverage or someone trying to chop through a cinder block with a chef's knife (wrong tool for the job).
I'm reminded of a thread some years ago discussing horizontal vs. vertical scratch patterns in a knife blade, and whether/how much they affected the blade's overall strength. The folks who were most adamant that it made a huge difference cited a 50-year old text on how airplane wings were
constructed... well I'm sorry guys, but a knife blade isn't an airplane wing or turbine blade or a screw from a giant tanker ship. While all the same concepts obviously do apply, the pieces themselves are entirely different animals.
Far more than "grain flow", what's actually useful and important to remember is, the simple fact that grinding a complex shape like a crankshaft out of a huge block or a proper kukri (not just a kukri-shaped machete) out of a very wide bar wastes an
awful lot of material. Even with a relatively simple knife shape, a bladesmith who can skillfully forge it very close to its finished shape wastes very little steel, whereas a stock-removal maker like me ends up literally throwing away roughly half of the bar he started with. That's just the nature of the beast... I'm
removing stock.
On a 4" long by 3/32" thick blade, that's not really a big deal. But when you start grinding 10" long bowie blades out of 1/4" or 5/16" stock, it results in a lot of money laying on the floor in the form of completely useless steel dust and belt grit.
In the pictured Condor kukri it was accepted that the breakage was the result of an inclusion and a faulty heat treatment. Those things can happen with forged knives as well.
Right... it's pretty clear that the grain in that broken knife is extremely coarse, and that's going to cause massive problems no matter how any given piece was forged, machined or even cast. That example is irrelevant to this conversation, because it's very obviously a heat-treat issue, not a shaping issue.
Ah, but you're not seeing that if the grain flow was optimal, it could be made several points harder, several ounces lighter, or with a steel that doesn't need to be quite as tough as 5160.
You're introducing completely different factors that really have very little to do with grain structure or "flow". Hardness, weight, and the inherent characteristics of whatever steel the maker started with are almost entirely irrelevant.
You have to compare apples to apples to figure out how much difference there really is between one factor and another. Tasting whiskey is not very helpful when trying to decide which wine is better...
Likewise, when discussing Nepalese kukris, it's important to keep in mind that those cats are very seldom using fresh, new steel... they're using old beat-up leaf-springs and whatnot, that have been subjected to who-knows-how-much stress and material fatigue long before the bladesmiths ever got their hands on them. So once again... there's no fair comparison to be seen (they're starting out with the deck stacked against them material-wise anyway, and we have few if any examples where the same piece of steel was used to make two knives, one forged and one ground).
I suspect you may be thinking of "grain structure" in steel, like the grain in a piece of wood.
It just doesn't work that way, unless there's a boatload of inclusions (see "A) Inherent Flaws" at the beginning of this post), as mete explained.
So sure, if you had a choice of an industrial scale knife forging company's product, why not? Don't see that around though.
Actually, we do see that
very often in the kitchen knife market. A high percentage of very well-known European and Japanese chef's knives with integral bolsters are forged to shape and then finish-ground, simply because - just like a crankshaft- that's the most cost-effective way to make them. Not because it makes an inherently stronger knife.
Sorry for the long-winded and mostly repetitive post... I'm not trying to lecture anyone, it's just that thinking these things through and typing it all out helps me keep it all clear in my own head.
Almost anyone can take a piece of whatever steel they can get ahold of and grind off enough steel to reveal the blade awaiting inside and then send it to Peters or Bos facilities for heat treatment, it takes a master smith to understand the science and underlying art in forging a piece of steel to enhance and showcase a piece of steel at its climactic capabilities.
There is no such thing as the "climactic capability" of a piece of steel. As JS Karl Andersen was quoted earlier, the steel is as good as it's ever going to get when it comes out of the mill, and the best
any maker can do is not screw it up too much.
Quite frankly, I find your comment more than a little offensive. I think you'd be pleasantly surprised to find out how many makers who
"just grind until it looks like a knife and send it off to someone else for HT" take all of this
very seriously, and devote thousands of hours of unpaid study to
everything involved in making an excellent knife. I invite you to talk to folks like Bob Dozier or Chris Reeve, and see how they feel about that statement. I never met him, but if the late great Bob Loveless was still with us, I have a pretty good idea what he'd have to say on that matter.
Claiming that only mastersmiths understand the science involved in making excellent knives is not only short-sighted and ignorant, it's just plain rude. :thumbdn:
