BRKT Rogue Review. Looong, looots of pics

[bigbcustom]

Have you ever used a Forrester?, and if so, how does the rogue compare?

 

[Gramps]

GREAT review HoB....and the knife appears to be very efficient at splitting wood under your technique. I am learning a thing or two from you and appreciate the lesson.

-best regards

 

[Cliff Stamp]

Well, the edge neither rolled nor chipped and the tip held despite its acuteness.

Problems with retained austenite only take place after extended use as it will transform to untempered martensite understress. You will hear arguements for retained austenite for toughness and indeed it does increase the impact tough in as-hardened blades, but as-used blades it is much worse.

... the elegance of the full convex grind.

I never did find it overly appealing, likely because I find flats more difficult to grind. It is easy to take a knife and turn it into a full convex grind, just put it in the slack region, I did this to a SAK awhile ago. However grinding a really even flat with a distal taper it much more difficult and thus I appreciate it more. I'd probably look different at hollows once I tried to grind them as well as it would seem to me to be even more difficult that a flat. Alvin says it is dead simple though.

I don't know what you mean or estimate the dynamic balance?

It is where a point mass has the same period of rotation. It corrosponds to a number of physical properties like precision of handling of that point, vibration of impacts, and issues with handling the blade.

That of course depends on the 7" knife and the 10" knife.

Yes, I was speaking of knives which were similar in design and equally optomized for a given set of tasks with the only real difference being the length. Not for example comparing a 7" cleaver style blade with a 10" slender bowie as there the 7" blade could easily have better ability to power through a 2x4.

I would expect chopping ability at least quadratic in length.

It depends on what you are chopping either really light material or really rigid material as you need corrospondingly maximum speed (tip cuts) or maximum inertia (cuts near the static balance point). Rotational tip speed is proportional to length but that is only part of the total energy and the linear part isn't dependent on length at all. The power has more to do with the total mass and the balance points and you can vary these a great deal in a given length, but at most you are looking at a less than linear effect. The 75% comes from actually comparing a number of similar blades of varying lengths which I did before I looked at the physics, experimentalist after all. Swaim looked at this on rec.knives years before I did. He also assumed there would be a bigger influence on length. Note as well that the total length is what factors into things like the inertial moments.

[thicker profile]

It also helps reducing binding.

Yeah, it also makes it harder to drive the blade into the wood though so there will be a sweet spot between the opposing effects. This is different for different woods. I find the 1/8" machetes near useless for splitting black spruce, just like you propose in the above, the thinner profile (and flats), make the blade stick badly.

-Cliff

 

[HoB]

JDBlade: I loooove the Settler. Almost bought on, might still buy one, but my favorable experiences with A2 in the Mini Canadian made me very partial to getting another one in A2. The Settler is made only in 12C27 if I am not mistaken?

Bigbcustom: no unfortunately not, I would love to take one for a whirl. It is bound to be a very different knife though: 3" longer and almost 2.5 times heavier!

Supposedly, there is a larger version of the Rogue in the works which might bridge the gap.

Gramps: As you say, to each their own .

 

[HoB]

I never did find it overly appealing, likely because I find flats more difficult to grind. It is easy to take a knife and turn it into a full convex grind, just put it in the slack region

True, but for a machine a flat is much easier than a curve. To me the appeal is more in how the light reflects of the blade. One blade that is ground like the Rogue's the reflection are constantly changing curves, on a flat they are "boring" straight lines. But obviously that is just personal appeal. But I understand what you mean, your appreciation goes up once you understand the difficulties and challenges involved.

It depends on what you are chopping either really light material or really rigid material as you need corrospondingly maximum speed (tip cuts) or maximum inertia (cuts near the static balance point).

Very true, I have experienced the same on this very Cherry when it first came down. I could not make any headway on the many, many thin (0.5-1") branches with a hatchet since they would simply bend away, which made me looking for a longer blade for yard work. After reprofiling the RD9 fills that role very well (though a Golok might have been better still) and takes those branches clean with one swipe.

For those who know their woods: The mystery wood looks like aromatic cedar and smells like aromatic cedar. But all aromatic cedar I have seen sofar is soft and light (internet says around 0.36 specific gravity). This one is pretty hard ,very closed grain (the surface of the cut is beautifully smooth and shiny), and the specific gravity I just measured to 0.62, so what is this ???. I mean this is no lignum vitae but it approaches hickory in density.

 

[Cliff Stamp]

True, but for a machine a flat is much easier than a curve.

Busse has started machining convex grinds, I have not seen a detailed comparison of the implementation vs the traditional belt finish though.

-Cliff

 

[db]

Quote:

Originally Posted by HoB

I don't know what you mean or estimate the dynamic balance?
It is where a point mass has the same period of rotation. It corrosponds to a number of physical properties like precision of handling of that point, vibration
of impacts, and issues with handling the blade.


I am still not sure what this is or how to find the dynamic balance point. Is it related to the balance point of the knife?

 

[hardheart]

I think possum linked a video of it, if I got this right. He attached a couple pins at the guard of his knife, and set it on a little jig on a table, which would allow the blade to swing point down like a pendulum from the guard (around the point it would rotate when swung in hand). He also attached a weight on a string at the pins. He set them both swinging, and changed the length of the string until the knife and pendulum were swinging in time. The length of the string/corresponding point on the blade to where the weight was swinging, marked the dynamic balance point.

I think.

 

[Cliff Stamp]

Is it related to the balance point of the knife?

It is a balance point, but it isn't the static balance point which is the center of mass. The dymanic balance point can be found as Possum has demonstrated which is how you would do it in shop on a test blade. If you use the knife you will know where it is quickly because impact vibration gets excessive outside of the dynamic balance point.

-Cliff

 

[bigbob68]

Thanks for the review, I think I'll have to pick one of those up since I am in the market for a nice fixed blade. I have found the micarta for $100 or the fancy walnut burl for $130.

 

[knifetester]

Very nice review, thanks for taking the time-it really shows

 

[jaislandboy]

thanks for the review and pics HoB....very informative....

 

[BillL]

Hi Cliff,

Can you elaborate on this:

"Problems with retained austenite only take place after extended use as it will transform to untempered martensite understress. You will hear arguements for retained austenite for toughness and indeed it does increase the impact tough in as-hardened blades, but as-used blades it is much worse."

Thanks

 

[Cliff Stamp]

The first step in hardening steel is to get it very hot (above 1450 F) which transforms it to austenite which dissolves a lot of the alloy. When quenched this alloy allows transformation to martensite. However if the quench is stopped at room temperature on a high alloy steel a lot of the austenite will not transform, as much as 20-30% is retained in high alloy tool steels.

This austenite is fairly soft and tough so the toughness will be fairly high. This is why some makers have argued that cold treatments make steels more brittle and it does in that respect (there are some complications however) but this only holds for the steel right after it is tempered, it is very different if you look at knives after extended use. This is one of the more common misconceptions about cold treatments and retained austenite especially for swords.

The austenite is meta-stable which means it will transform to martensite with time all by itself and that any strain on the knife will increase this reaction. This is expecially critical for hard use knives which see a lot of impacts, prying and similar. As the austenite transforms to martensite you have a blade which not contained martensite which is not tempered and untempered martensite is so brittle that it can crack under almost no stress at all.

In short, transform all the steel to martensite and then temper to the optimal hardness. If the desired toughness can't be achieved that way then use a different steel, this is why there are so many of them.

-Cliff

 

[BillL]

Cliff,

Would this problem be applicable to all steel?

Are different steel affected to different degree?

What is the time span when the austenite transforms.

Thanks