CBN Rods

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Cliff Stamp
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CBN Rods

Postby Cliff Stamp » Fri Mar 21, 2014 5:00 pm

I normally prefer to wait longer before discussing something to confirm/ensure conclusions, but since a few people asked, here is some information. Please be aware that the data is very sparse at this stage so don't draw overly strong conclusions from it. All work was done using the Sharpmaker with the 20 dps setting (for maximum operator benefit) .

Image

This is a high magnification shot of the surface of a medium rod, the scale is in the picture (credit to Clay Allison for convincing me to stop being so lazy and to put it in there). Here is the CBN rods at the same magnification :

Image

The grit size difference is obvious, you can even measure the exact grit size of the CBN as you can just see the grains clearly. Note as well they are fairly evenly distributed and not subject to extreme mass clumping. This is confirmed if you just feel the rods, they are rough yes, but they are not highly irregular.

Note as well that the 400 mesh or sieve rating appears to be correct as the particles are of the order of 40 microns which is the approximating micron rating for 400 mesh.

For reference, here is a 240X SPS-II waterstone :

Image


Image

This is the edge on a Mora #1260 (the number doesn't mean anything, it is just the model number) which is 1095 at 58-59 HRC (as spec). It has been flattened and the edge apexed with a Bester 700 grit waterstone, using the hone-to-dry method to maximize the edge finish. Note the :

-uniform scratch pattern
-even edge line
-small irregularities

I then cut the edge off by making three slices into the same stone to mill a flat on the edge. This is the result of just 10 passes per side on the CBN :

Image

The edge is brought to an apex immediately and will slice newsprint but won't shave and the edge has some pieces knocked out of it as would be expected. Here is the result of 6 more passes which are done using ultra-light honing (5-10 grams) on the CBN rods :

Image

Note the edge is refined and now it will shave, but it is really coarse, even a wet shave isn't likely to be comfortable. I cut the edge off again (same process, 3 cuts into the 700 grit Bester) and just for comparison apexed it with the medium rods. This time it took 130 passes per side :

Image

The edge is significantly more polished and shaves well and does all the things you expect from the Spyderco medium rods (3-finger sharpness test passes readily). Note that the bevel now is about 0.1 mm side and you can see it by eye.

As another comparison, to see if you could jump from the CBN right to the medium rods I cut the edge off again (same process, three passes into the 700 grit bester) and then apexed the edge with the CBN rods. As the edge was much thicker/wider now it took 30 passes per side to apex.

(I don't have the diamond rods, if I did I would have interjected them here).

I then switched to the medium rods. After 10 passes per side there was a significant difference in finish, after 30 passes per side it was back to the Spyderco medium rod finish. To clarify now, I am working on a very narrow bevel, it is still only about 0.1 mm or so wide.

In short :

-the rods are fairly coarse, a 400 mesh/grit rating is a decent approximation to the type of finish
-they cut much faster than the medium rods
-in order to jump from the CBN to medium rods the bevel would have to be very narrow
-the edge from the CBN rods can be sharp, it isn't just shaping only
-the abrasive is well distributed

A immediate recommendations / observations :

-use the CBN rods to set the relief only, use the medium rods as the micro bevel

If the diamonds are inbetween then you could use them. If you try to polish the CBN bevels with just the medium rods you are likely going to be at it awhile. I will measure this later.

In regards to issues, there is only one :

There were a couple of points where the surface was rough enough to snag the edge. Do not, and this is critical, try to resolve this by just grating the edge hard against the rods, this will just tear the grit off the surface. For the first sharpening use the highest carbide knife you own which is fairly dull (or that you want to reset the angle). Work it light and slow and this will even out any of the coarse spots.

(the reason that you do not want to use a low carbide knife is because it will be cut much easier which means much deeper and you could just pull out the high spots and you want to wear them down rather than just pull them off or crack off a large piece)

If there is any thing in particular of interest just let me know.
Last edited by Cliff Stamp on Sun Mar 01, 2015 10:43 pm, edited 1 time in total.

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D1omedes
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Postby D1omedes » Fri Mar 21, 2014 5:53 pm

Thank you for the sharing of the data you have discovered so far, Cliff. I find any possible new additions to the Sharpmaker very exciting.

Are the CBN rods similar to the alumina ceramics of the brown and white rods? In essence, will CBN wear away over time or break off (as has been reported on the diamond rods)?

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Postby tvenuto » Fri Mar 21, 2014 6:20 pm

Thanks for the info. Love macro pics!

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Postby Henry - get both » Fri Mar 21, 2014 6:47 pm

Can we see some non macro shots of the CBN rods?

I hope Spyderco puts out some 800 mesh CBN rods.

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Postby mattman » Fri Mar 21, 2014 7:09 pm

Thanks, Cliff... much appreciated review.

I will pick these up as soon as I know where to get a set!

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Postby Cliff Stamp » Fri Mar 21, 2014 7:38 pm

Henry - get both wrote:Can we see some non macro shots of the CBN rods?
Image

and :

Image

I hope Spyderco puts out some 800 mesh CBN rods.
Solid CBN would be interesting, cost would be an issue.
D1omedes wrote: Are the CBN rods similar to the alumina ceramics of the brown and white rods?

The alumina stones are solid sintered products meaning that you are unlikely to wear them out in your lifetime, or in fact even wear them enough they need to be lapped, the CBN ones are a plated product, there is a single layer of CBN which has a nickle electroplated bond. This is a very common form of the abrasive (along with the solid vitrified bond).
In essence, will CBN wear away over time or break off (as has been reported on the diamond rods)?

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Postby bearfacedkiller » Fri Mar 21, 2014 7:51 pm

I wonder how soon I can stop into the SFO and pick a set up? Thanks cliff, again. :-)

I might just put, "Thanks Cliff" in my signature. Save myself some time. lol!!
-Darby
sal wrote:Knife afi's are pretty far out, steel junky's more so, but "edge junky's" are just nuts. :p
SpyderEdgeForever wrote: Also, do you think a kangaroo would eat a bowl of spagetti with sauce if someone offered it to them?

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Postby jabba359 » Fri Mar 21, 2014 7:55 pm

Cliff Stamp wrote:The edge is significantly more polished and shaves well and does all the things you expect from the Spyderco medium rods (3-finger sharpness test passes readily). Note that the bevel now is about 0.1 mm side and you can see it by eye.
I don't recall reading before what the 3-finger sharpness test is. Could you please elaborate?

Thanks for sharing your impressions on these.
-Kyle

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Postby mattman » Fri Mar 21, 2014 8:02 pm

jabba359 wrote:I don't recall reading before what the 3-finger sharpness test is. Could you please elaborate?

Thanks for sharing your impressions on these.
Kyle-
It's Murray Carters test...

Should be able to Google from there...

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Postby jackknifeh » Fri Mar 21, 2014 8:15 pm

jabba359 wrote:I don't recall reading before what the 3-finger sharpness test is. Could you please elaborate?

Thanks for sharing your impressions on these.
The 3 finger test was started (as far as I know) by Murray Carter (cartercutlery.com). He has a description of how to do it and what to look or feel for. To get any benefit from the test you will need to perform it on about every knife you handle. A lot of the info the test will tell you is actually a comparison with other knives. You need to perform the test on knives of very different sharpness and edge type (toothy vs smooth) to be able to feel what the test shows. Once you can tell the difference you can determine the sharpness of an edge by doing this one test. Personally, the only thing I can determine by performing the test is if the edge is toothy or smooth. Both could be very sharp. A dull edge will allow the skin to slide along the edge but so will a razor sharp smooth edge. The toothy edge however will grab the skin creating resistance to being able to slide the skin along the edge. Yup, along the edge, not across it. Don't worry, you won't cut yourself if you do it right. Read Mr. Carter's explanation for accuracy's sake. :)

Jack

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Postby mattman » Fri Mar 21, 2014 8:26 pm

Thanks, Jack.

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Postby Henry - get both » Fri Mar 21, 2014 8:43 pm

Thanks Cliff.

Im looking forward to trying these. Back in 2007 Sal described the diamond triangles as 400 mesh, 10th post in this thread:

http://www.spyderco.com/forums/showthre ... extra-fine

A long term comparison between the diamond and CBN triangles would be interesting to me.

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Postby Cliff Stamp » Fri Mar 21, 2014 8:51 pm

jackknifeh wrote:The 3 finger test was started (as far as I know) by Murray Carter (cartercutlery.com).
He didn't start it, but he certainly popularized it and described it with more detail than most.

It is very common for people to argue that you can judge sharpness by how an edge feels, what Carter did was fairly critical for a few reasons.

a) he realized that a knife can shave and still not be sharp as the edge can be rounded and thus slice very poorly

b) there needs to be some way to quantify how an edge feels to allow one person to communicate it to another

Most people don't do the second and don't understand the first part.

The test is extremely basic and it is no more than this :

-you put your fingers on the edge of the knife and see if you can draw them along the edge and not get cut

When people read that it sounds insane, of course you can't do that, what happens if a knife is sharp then you would slice your fingers open. What Carter argues is if the blade is really sharp then you will not draw your fingers at all because you will stop. This sounds frankly idiotic but you can actually do it and it does allow you to readily separate a knife which has a rounded edge vs one that doesn't.

Now can you slice your fingers open, sure - but I knew a guy who ran over his own head while driving a car so lots of things are possible.

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Postby Cliff Stamp » Fri Mar 21, 2014 8:52 pm

Henry - get both wrote:
A long term comparison between the diamond and CBN triangles would be interesting to me.
I will see if I can't find a set of the diamond rods.

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Postby Blerv » Fri Mar 21, 2014 10:32 pm

So these are more coarse than the diamonds?

If that's accurate it's very interesting. Would you say they are a suitable replacement or simply another tool in the Sharpmaker belt?

Thanks a ton, Cliff!
:spyder: Blake :spyder:

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Postby jabba359 » Fri Mar 21, 2014 11:31 pm

Thanks everyone for clarifying the 3-finger test. Surprisingly, I hadn't heard of it before. Guess I learn something every day. I suppose the name comes from how many fingers I would have left if I do the test wrong! :D
-Kyle

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Postby Clip » Sat Mar 22, 2014 12:18 am

Cliff Stamp wrote:but I knew a guy who ran over his own head while driving a car so lots of things are possible.
I'm tempted to say pics or it didn't happen...but I'll just take your word for it.
Click here to zoom: Under the Microscope

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Postby bearfacedkiller » Sat Mar 22, 2014 12:01 pm

Blerv wrote:So these are more coarse than the diamonds?

If that's accurate it's very interesting. Would you say they are a suitable replacement or simply another tool in the Sharpmaker belt?
I am wondering the same thing. I already have the diamond rods and wonder what the difference would be. I'll probably get a set just to see for myself anyway.
-Darby
sal wrote:Knife afi's are pretty far out, steel junky's more so, but "edge junky's" are just nuts. :p
SpyderEdgeForever wrote: Also, do you think a kangaroo would eat a bowl of spagetti with sauce if someone offered it to them?

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Postby Cliff Stamp » Sun Mar 23, 2014 2:11 pm

Clip wrote:I'm tempted to say pics or it didn't happen...but I'll just take your word for it.
I did not witness it but as the story goes ... he came home one night fairly drunk, tried to steal his fathers car, was caught in the act, jump out with the car in gear, slid and fell back and the tire skimmed the side of his head and ripped off a fairly large chunk of hair. Now he could have just made it all up to explain why he suddenly was missing a big piece of hair and skin - but if he did, good on him for that anyway as it was pretty entertaining.


[video=youtube;xRQQgwRMDfU]http://www.youtube.com/watch?v=xRQQgwRMDfU[/video]

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Postby Surfingringo » Sun Mar 23, 2014 2:38 pm

Do you have any data on how these compare to the diamond rods Cliff?


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