Update on Metallic Bonded CBN stones.

[wade7575]

I was talking to Konstantin from Gritomatic and he said his 50 grit is the fastest cutting stone he has and he said his did not like soft steel but it cut fast on M390 and D2 I have have some M390 stuff and I'll see what it does on it.

 

[bucketstove]

I would say the F150 was around 3 times faster than the F80, on my CRKT 440c blade. I pushed hard enough, say 1 lb, that if it was going to work it would have. Not being my stone and being resin bond I was cautious, ..

Hi,
how wide was the bevel?

 

[wade7575]

Pretty wide and I'd guess it to be 4 to 6mm because it was planer blades don't forget and they always seem to have a wider bevel then a knife for sure.

 

[Diemaker]

Hi,
how wide was the bevel?

.06"

 

[Gritomatic]

Let me tell what I know at the moment. The sharpening performance below 120-150 grit starts to diminish. It happens with all existing bonded abrasives but bonded CBN & diamonds are much more remarkable because the number of exposed particles drops significantly on 50-60-80 grit. The weight concentration of CBN 50 and Venev 60 are doubled, but they have less exposed particles anyway. The advantage of 50-60-80 grits is the grain size. In some conditions larger grain size gives the performance boost, in other conditions it's useless. It's very steel-dependent. I have been said that the issue is the most visible on elastic steels like 440 because large grains do not remove metal from the surface.

Wade, please test CBN-50 on different steels.

 

[bucketstove]

Let me tell what I know at the moment. The sharpening performance below 120-150 grit starts to diminish. It happens with all existing bonded abrasives but bonded CBN & diamonds are much more remarkable because the number of exposed particles drops significantly on 50-60-80 grit. The weight concentration of CBN 50 and Venev 60 are doubled, but they have less exposed particles anyway. The advantage of 50-60-80 grits is the grain size. In some conditions larger grain size gives the performance boost, in other conditions it's useless. It's very steel-dependent. I have been said that the issue is the most visible on elastic steels like 440 because large grains do not remove metal from the surface.

Wade, please test CBN-50 on different steels.

Hi,
Elastic steels?
Does using oil change boost production?
What is the working pressure these metallic bonded cbn stones are supposed to take?
How come the advertising/description doesn't mention this?

 

[Bill DeShivs]

Maybe if you used more periods it would cut better.

 

[bucketstove]

Maybe if you used more periods it would cut better.

Thats just moving the bleeding around

 

[Blues]

Maybe if you used more periods it would cut better.

Perhaps it would be better for you to concern yourself with half stops instead of his use of full stops.

Let's please not use this forum and its threads for criticizing one another. Take private matters to PM.

Thanks.

 

[Gritomatic]

Elastic steels?

https://en.wikipedia.org/wiki/Plasticity_(physics)
Low-carbon steels have more plasticity - they can self-cure groves of abrasive grains. High-carbon steels have less plasticity. I'm not a metallurgy expert, it's just my assumptions.

How come the advertising/description doesn't mention this?

I have started to gather information from different sources after Wade message. I want to learn something new just like everyone else here. When we understand the limitations of extra coarse grits, we will edit descriptions. It's definitely not about "50 grit is bad for everyone".

 

[M-S-T]

Ok. I will try to share my personal experience with low grit cbn/diamond stones. In general, when it comes to heavy reprofiling 9 times from 10 I reach for 200/160 micron stone. If I need just to do little of reprofiling , (like fixing the angle of the tip ) I will go for 100/80 micron stone. Ususlly I switch between them depending on the work that needs to be done. And I believe that there is no practical reason for a regular Joe buying something coarser.
I can hardly imagine the volume of reprofiling that 200/160 stone would not handle. I have a 315/250 diamond stone and honestly, I have used it 2-3 times in 5 years. I used it to put a new edge on the custom-made bushcraft knives made from Vanadis10 and Vanadis 4. I could make it with 200/160 but I was just curious how it will behave. And it worked really well.
I have used 400/315 stone, but I did not liked it ( or I could not find any use for it) I have sold it for a knife maker, who is making hunting knives from all kind of high vanadium steel and he uses it regularly for putting e new edge on his knives.

 

[M-S-T]

Part II.
When you are working with very coarse diamond stones you need to be aware of the "angle of the attack". If you are reprofiling a knife (let's say from 40 to 30 degrees included). You are removing the steel from the top of the edge downwards the apex. This way you will have no problems since you don't want to reach the apex with your coarsest stone anyways (most of the time). In the situations, where you want to make a steeper angle and for some reason you have decided to start with a very coarse stone you can get an earlier mentioned phenomena, when your stone just struggling, jumping and don't want to work. It is because the angle of attack is so high and the particles of diamond stone are so big that you need a huge amount of force and pressure to make it work which is not practical in most cases. So you have to work around it. Also, for some reason ( I will not pretend that I know why) cbn/diamond stones work like S**T with some types of steel. Maybe it is related to heat treatment, maybe to some specific steel chemistry or maybe it is a combination of both. So in my opinion, you can not say that super low grit stones have no use. They do. Just not that often.

 

[scottc3]

MST, to read that a blade maker is setting edges on new blades using a 300/315 CBN/diamond, I gotta ask, using power or by hand?
I am amazed how well the high vanadium steels are holding their apex with our three generations of users, with just a bit of honing. I am amazed! Specifically, we have not had to do anything but hone on Sharpmakers white fine stone since profiling to either 30 or 40° inclusive- some use cases closing in on a year, one use case every year for multiple years.

Just got the beast 50 grit from KME along with a standard KME stone set and Venev bonded diamond kit.

Having already read about extreme course grit blade re-profiling, and never having had a problem reprofiling with either the KME 140 grit or 300, depending on steel, I got the beast to make quick work of initially shaping super steel bevels, where the 140 has given good service with vanadium steels four percent or greater. So the need for it was curiosity as much as practical, as I began learning by doing (natural inclination as a pup) until I could add academics and experience for planning and managing, to get in front of the learning.
The motivation for the standard stone set was to teach my 11-year-old to sharpen the likes of 8Cr, AUS8, and N680... I keep my mouth shut at this point when it comes time to hone over and over again on his spectrum of steels. They are as perfect as steels can be for his learning curve (along with "I temporarily" / "yeh its gone", lost it curve).
I have not had the time to use the Venev bonded diamond set, as mine is one of the first sets to come out of that factory outside Gritomatic's stated OEM spec for flatness (0.00787" or 0.2mm), measured at about 0.20 to 0.24" on the whole set plus a 1200 grit bought separately from Gritomatic's Big River store. That 1200 grit big river stone measuring exactly as the one in the set, slightly bent as stated, worked perfectly to bring out the LED Christmas lights reflected on an Adamas brought to the sharpest I have ever experienced benchmades D2. Because of this I'll probably start in my use of the Venev bonded diamond kit stones by simply sharpening knives, first from the kitchen than from folders softer steel families and finally a beautiful chunk of m390 on my Contego, BEFORE flattening. My guess is, at least up to 1200, they will work just fine as is; the proof is in the pudding. I admit to a very strong bias for stones versus films and liquid diamond carriers. Stones last and last and last, as long as you take care of them.​

 

[M-S-T]

Yeah, he is setting bevels with a guided system. TSPROF I believe. You know when you are dealing with old school thick hunting knives made from Vanadis 10, cpm125v and 15v (with custom HT and cryo) you start to appreciate coarse stones . Venev stones can be way more curved than 0.2mm

 

[bucketstove]

https://en.wikipedia.org/wiki/Plasticity_(physics)
Low-carbon steels have more plasticity - they can self-cure groves of abrasive grains. High-carbon steels have less plasticity. I'm not a metallurgy expert, it's just my assumptions.

Hi,
How could self-healing explain a 250 micron abrasive being 3 times slower than 125 micron abrasive?
I'm pretty sure it doesn't work like that, just look at any relative grindability chart (abrasion wear resistance).
The softer metals always grind easier/faster than the harder metals.
The higher the carbide volume, the lower the grindabilitity, it takes more time/pressure to remove material, less is removed with each pass , more abrasive wear resistance.
It holds for alloys/coatings...
Manufacturers selling CBN wheels say they're for hardened steel 50HRC and harder
wade7575 is sharpening M2, and diemaker is sharpening 440C, both are high carbide volume (5%+) so not exactly "plastic"

I have started to gather information from different sources after Wade message. I want to learn something new just like everyone else here. When we understand the limitations of extra coarse grits, we will edit descriptions. It's definitely not about "50 grit is bad for everyone".

Hi,
I look forward to seeing what you post, esp what the manufacturer has to say regarding the pressure .

I too am a big believer in everything is useful for something, but what is that for this stone?
Or for 250 micron grit superabrasive stones (diamond/cbn stones) ?
Or for any kind of 250 micron grit sharpening stone?
What is the advantage of larger grain size if its not speed?


As a next experiment for wade/diemaker, maybe compare ~250 micron sandpaper to ~125micron sandpaper,
or only ~250 micron sandpaper to ~250 micron cbn/diamond (see if sandpaper is faster than cbn/diamond).

 

[Gritomatic]

What is the advantage of larger grain size if its not speed?

Speed must be the only advantage of very coarse grit.
We have ordered 500-micron metallic bond diamond. We will test it against 200 and 100-micron to understand the usefulness of ultra-coarse grits.