CGSW for KME Review

[3D Anvil]

I wasn't thrilled with the coated diamond plates that came with my KME, so I recently picked up a set of bonded diamond stones from Columbia Gorge Stoneworks (CGSW). They're available from Gritomatic and the full set (160, 80, 40, 20, 10, 5 micron) costs $160, which is a pretty good deal compared to the Venev set which goes for $225.



First impressions
My first impressions of the stones was ... not good. They didn't seem to cut at all and it felt like trying to sharpen with a pool tile. Clearly the stones needed to be lapped before use, which is a bit of a drag but not a big deal. 30 minutes later, after going to work with a piece of float glass and 120 grit silicon carbide powder (more on that later), I was starting to enjoy my purchase. There's no break-in with these stones as there is with coated diamonds, which can be harsh for the first few sharpenings. If anything, the bonded stones seem to be cutting better with use. Granted, I've only used them on five blades to date, but several of those involved lowering the bevel angle several degrees, so there was a fair amount of work involved.



In use
The 160 micron is the coarsest stone, which translates to about 90-120 grit in general grit parlance. I didn't get the best performance out of it until I lapped it with F60 silicon carbide powder. Even now the 160 micron isn't super aggressive and if I need to remove a lot of material I find I'm better off starting with the Shapton Pro 120 stone, which doesn't load up as fast and can take some muscle. Once I get very close to the apex I switch to the 160 micron and it makes quick work of the last bit while refining the scratch pattern.

From that point I'm just going through the grit levels. I find about three passes per side is sufficient, and I'm using edge leading and trailing strokes, which is contrary to CGSW's recommendation, which is to use edge trailing only. Maybe that would be better, but life is too short. In any case, I'm very happy with the results I'm getting now. I should mention that I'm using water as a lubricant, which is recommended by CGSW. I may switch to a light oil because the stones absorb zero water and it's very hard to keep water on them.

I find that the stones above the 160 micron level cut reasonably quickly. They also load up fairly quickly and I find myself cleaning them with water and a rust eraser after sharpening one side. That may be overkill, but it's what I'm doing right now.

What it gets you
If you go through all of the stones you end up with a near-mirror finish -- very nice indeed. In fact, I found that the appearance of my edge was getting worse when I followed the 5 micron stone with KME's 3 micron lapping film! At first, I thought it was my imagination, as the lapping film ... even a 6 micron film, let alone 3 micron, should produce a better result than a 5 micron diamond stone. So I finally whipped out my handy-dandy USB microscope, and this is what I found:


Above is the bevel after the CGSW 5 micron stone.


Above is the bevel after the KME 3 micron lapping film.

Say what? Clearly the CGSW abrasive is more uniform than KME's lapping film. What's more, I found the same result with the KME 1 micron lapping film! In contrast, I found that the KME kangaroo strops with .5 and .1 micron CBN emulsions worked great and produced a true mirror finish. In the future I will drop the lapping films and go exclusively with the kangaroo strops and emulsions.

Final thoughts
Of course, you might not want to spend the time to get a mirror finish, or you might simply prefer a toothier edge. In that case there is no reason to go beyond the 20, or even the 40 micron CGSW stones, which produce a sharp edge and a nice satin finish.

Unfortunately I can't compare these stones to the Venev equivalents, which I haven't had the opportunity to try, except to note that the Venev's are more expensive. They also have a thicker layer of abrasive (2mm vs. 1.6mm for CGSW). My impression is that thickness of the abrasive layer isn't an issue, however, as the CGSW resin is extremely hard and I expect that the stones will last many years, and will perhaps outlive me.

As far as cleaning the stones goes, the manufacturer (who I believe is a member of this forum under the screen name "diemaker?) recommends using rubbing alcohol, although he says the discoloration doesn't affect performance. Because the stones are so hard I don't think they will have to be lapped/flattened often. I would guestimate after maybe 15-20 blades, but that's just a guess as I haven't gotten to that point yet.

It's worth mentioning that CGSW is also the producer of the well-known Edge Pro Matrix stones, and I would assume that these KME stones are essentially identical to those, aside from being 2" shorter and about half the cost!

Conclusion
In conclusion, I highly recommend the CGSW bonded diamond stones for KME. They appear to be quite durable, they cut reasonably quickly, and they produce a superb finish. They cost more than the KME Gold coated diamond plates, but I think they will last at least four to five times as long.

Result:

 

[Diemaker]

Thank you for purchasing these stones and your review!!! First I would like to say a few things that I noticed in your photos.

In your second photo third stone up from the bottom it "looks like" it didn't get completely dressed. It looks like the perimeter is dressed but the center still has the as-molded surface.

In your first microscope image, those stray scratches are most likely from edge leading passes catching the burr, pulling it between the stone and bevel, and scratching the bevel in the process. Often I have seen these scratches point to a microchip in the apex. That chip or burr can become embedded in the stone requiring a dressing to remove it. The finer the stone the more of an issue this is, being most prominent with the 10 and 5-micron stones. If you stick to edge trailing passes only those stray scratches should disappear, if they bother you.

These stones are really sensitive to proper dressing, for good or bad but it is a fact. If they are not properly dressed they will not reach their potential, period! Until you figure it out it is a problem, once you figure it out it is an advantage as they are very easy to dress, the 1x4 stones only take about 10 seconds to take from worn and not cutting very well to completely fresh. I am sure you have not reached the potential of the 160 at all. The F60 abrasive is 260 micron, you really need a 36 grit minimum, which is 500 micron, but I would suggest 24 grit, which is 710 micron, so the abrasive has more room to get ground down before needing refreshed. I use around a 2500-micron pool filter sand for the 160m stones. F120 would be good for the 40m stone, I use ANSI 60 grit but fresh 240 grit works too. For the 20m and finer stones I use 240 grit. F120 will work fine but be gentle.

I don't worry about my stones getting dark, they get really dark after 20-30 knives but work as well as after the 3rd knife after being dressed. If the color starts getting shiny then it is time to clean or dress them. I find the 40m through 5m stones don't reach their full potential until the 2nd or 3rd dressing, but I am a minimalist when dressing, so don't be shy about using too much pressure or letting them get really dark from use so they need another dressing.

I have tried using mineral oil instead of water and it works fine. The only downside is it doesn't wash the swarf away as well as water and doesn't clean up as easily. It is nice that it doesn't evaporate like water.

The resin/diamond mix is the same as the Matrix stones except that 3 of the grits are a hint coarser so I have even micron ratings. The difference in price has to do with a few things, including they don't come dressed nor the ironclad EP customer service or satisfaction guarantee.

I don't mean to be bossy and hope that I don't sound way. Like any other stones they have their own peculiarities that you need to learn about and adjust to to get the most out of them, and these are certainly different.

Thanks again,
David

 

[3D Anvil]

Thank you for purchasing these stones and your review!!! First I would like to say a few things that I noticed in your photos....

Hey, I appreciate the advice! I will definitely find some pool filter sand for the 160. Being able to remove a lot of material on the coursest stone is a big deal for me, since I'm usually sharpening other people's knives and having to reset the bevel. As far as the stray scratches go, it's good to know the reason, and I may go to trailing strokes only for A+++ blades. For most knives, though, I'm fine with the tiny scratches, which are mostly worked out with CBN/stropping anyway. I think the bevel on the Esprit (posted pic) looks great, and that was ultimately going from the 5 micron stone to .5 and then .1 CBN. I'll be getting another kangaroo strop and I'll use 1.5 micron CBN in between the last stone and the .5, which should give an even cleaner surface.

Would you recommend F220 to dress the 20m and finer stones, rather than F120?

 

[Diemaker]

Yes on the F220, the stones will last longer being dressed with the finer grit. When setting bevels with the 160 be careful not to let the swarf build up as it will act like loose abrasive and wear the resin away prematurely. The coarser the stone the less they need to be dressed, as long as you don't use too much pressure. Keep in mind how much pressure you want to use depends on the size of the contact area being sharpened, small bevels on a curved blade means there is very little contact area. I normally start resetting a bevel with the 80 until I have a little bevel set where the old edge bevel and blade bevel meet before dropping down to the 160. This is a good idea with any coarse stone, not just mine.

Keep a bare leather strop handy, it is one of my favorites for most steels after the 5m stone. While it doesn't polish the bevel it is perfect for the last few thousandths at the apex to smooth and deburr.