Bk-9 failure

rifon2 said:
The Camillus BK9 was the same thickness as the current Ka Bar BK2 = a full quarter inch.
Click to expand...

Not to put too fine a point one it, but the current BK-9 is .188 (3/16") inches thick, whereas the Camillus version was .210 (13/64") inches thick — a difference of .022 (around 1/64").

In other words, the current BK-9 is 3/16" and the Camillus version was only 1/64" thicker, not a full 1/16" inch thicker.

Sorry, folks, but the Camillus BK-9 was never a full 1/4 inch thick.
 
Toooj, work hardening is not the problem. Take note of the comments about damage to planer blades from cutting hemlock. Despite the large number of hemlocks in the Catskills it's not harvested to any extent .When I asked my sawmill friend about this he said there isn't any real market for it and the" small hard knots damage the blades too often" !! And this comment from a man who mostly cuts the various hardwoods of the area.So don't underestimate the those knots !
While you may find things like inclusions involved they are just the weakest point .The real cause is the hardness of the knots and I also assume the forces involved especially a twist .Looking at photos of various batoning failures they often look to me like an off center hit putting a twist on the blade. A knot could put a similar lateral force if hit off center.
 
Hi Mete,

Thanks for posting. Knots, nails pounded into trees, hitting stones on the ground are all culprits I have found from investigations. Anything that can exceed the strength of the blade material. Also agree that lateral stresses (twists and angled hits) are biggies. This is particulary true since very few of us can claim to baton with the blade absolutely and completely verticle or hit the blade totally normal to the back. Ethan's post about being very careful with one's knives and tools is always sage advice.
On another note, do you live in the Syracuse area? If so, I think our paths have crossed.


Best Regards,


Paul Tsujimoto
Sr Eng
Prod Dev and Qual
KA-BAR Knives
 
Toooj, At some time I worked in Syracuse but now I'm retired in the Sullivan county Catskills.
I don't have a copy but somewhere out there on the web there is an article on how to break a perfectly made knife during batoning .Somebody please post it.
 
dawsonbob said:
Not to put too fine a point one it, but the current BK-9 is .188 (3/16") inches thick, whereas the Camillus version was .210 (13/64") inches thick — a difference of .022 (around 1/64").

In other words, the current BK-9 is 3/16" and the Camillus version was only 1/64" thicker, not a full 1/16" inch thicker.

Sorry, folks, but the Camillus BK-9 was never a full 1/4 inch thick.
Click to expand...

the literatures say 0.25 inches for various knives, including the Camillus BK-09 iirc, but it never quite seemed 0.25 ya know? 0.04 off? oh my!


Bladite
 
At some time I worked in Syracuse but now I'm retired in the Sullivan county Catskills.
Click to expand...

Mete,
I lived in Syracuse from 1978-1992. Have fun in the Catskills.



Best Regards,

Paul Tsujimoto
Sr Eng
Prod Dev and Qual
KA-BAR Knives
 
just for the record the planer blades that shattered while thickness planing hemlock, were 1/2" thick. caused damage to the holders and the feed inlet too.
 
Mete/Marantz,

Thanks for bringing this up and for posting. A good read for all who baton, which means most, if not all BeckerHeads.
When you are out in the wilderness and tired, cold and in a hurry to build a fire or a shelter; it just takes 1 careless hit and ....


Best Regards,

Paul Tsujimoto
Sr Eng
Prod Dev and Qual
KA-BAR Knives
 
Toooj, for you and other techies -The original question was about a knife with a half moon section broken out.Again to me that means torque impact .
If you'd want to experiment try this for transverse impact strength. Make a knife of a standard steel like 154CM and another of CPM154. One advantage of the CPM process is that the steel is isotropic [properties same in each direction] . Take each blade and baton off square. The CPM 154 should resist breaking out the half moon much better than 154CM. Something to do in your spare time ! Have fun.
 
moon shaped bits to me indicate shockwave fractures, given the thin nature of blades compared to rocks... i'm thinking generally of the myriad named patterns in flint knapping... in other words, crystallization ripples

http://en.wikipedia.org/wiki/Conchoidal_fracture


Bladite
 
the only becker i ever broke mas my cammie bk7 . its nicely reshaped and performs fine . has more of a bullish appearance now .
 
^ Gutsy, i would love to see pics of the bullnose BK7! post em up!

on the topic of damage, i have an ax that got DENTED by a knot I was bumping while harvesting salvage timbers. I damn near got beaned in the mouth and nose by the poll as the ax rapidly bounced off the knot. And this was a SOFTWOOD tree (cedar).
\
 
Hey Bushman and all...

If by cedar you mean Eastern Cedar Or Juniper I have encountered some of the damndest convoluted conglomerations of mixed up knotty crud you can imagine....I love the smell of the stuff and it is reputed to keep mosquitos at bay so I have split a bunch of it over the years and the knots of both the Eastern Juniper (Junipera Virginianus) and it's cousin the western juniper have incredibly hard knots. Amazingly, the outer white parts can be so soft they can be dented by your thumbnail......The lower, inner twigs and small limbs are some of the best fire starting material ever and, the dried bark when frotted is excellent tinder......Burn the knotted twisty crap whole if possible.....Saves a BUNCH of frustration......

All Best....

ethan

All Best....

ethan
 
I tend to believe it is more likely that the knife did NOT hit something harder then the blade or just very hard, but rather that a portion of the blade got stuck in the fibers in its penetration and the knife was being "rotated" somehow in the meantime (a likely movement during chopping, particularly if sloppy-chopping occurs). That, toghether with BK9 being really thin at the edge for a large knife such it is, brought to the breakage for me. The "half-moon" shape is something I have seen other times, and it usually accompanies well performing steels. I believe it is a matter of torque + geometry + bad luck in the end, and I apologize for not agreing with mr. Becker (which I admire greatly) or mr. Toooj.
 
Hey Chenko....

Disagree all you want......If was 100% right all the time I might feel differently but I WAS wrong once, etc, etc(lol).......Seriously, I think this type of fracture is most likely caused in the manner Tooj postulates but, your theory could easily explain some blade failures quite nicely and it is possible that it caused this one......The steel is pretty predictable but, the vagaries of Hemlock and Juniper much less so.....Thanks for your theory and your interest......

All Best....

ethan
 
Mete, Bladite and Chenko,

I'm enjoying a nice Easter break right now. Come Monday, I'll expound on what I have seen over the last 23 years of examining returned broken blades and experimenting with fracturing blades. Hint: we are all correct. There are multiple ways too break blades and some ways to determine which did what.


Have a happy Easter,

Paul Tsujimoto
Sr Eng.
Prod Dev and Qual
KA-BAR Knives
 
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