Diamond sharpening and Crbides

nozh2002

nozh2002

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We have discussion on Russian forum and this came up:
"Diamond sharpening rip off carbides from steel and sharpen just steel matrix, as a result at the begining edge is same as for simple carbon steel and after it wear out carbide teeth came out and start cutting - like postponed secondry sharpness."

What do you think?

Especially I am asking Pamela - what do you see in your microscope?

Thought agains this is that:
1. If Carbides are riped off then edge will have holes with size equal or bigger then carbides - fine edge will be hard to form.
2. Diamonds embeded in leather unlikely rip out Carbides embeded in steel.

Thanks, Vassili.
 
Hmm. Seems like the matrix would be the first to be removed since it is softer and that this would expose more fresh carbides instead of the other way around. It will be interesting to see but there are so many stories of successful sharpening and reprofiling with diamond pads and ceramic that it is hard to believe they do what you suggest.

I would hope that studies and research would have been done before marketing to determine the extent of this. But, you never know.
 
nozh2002 said:
Diamond sharpening rip off carbides from steel ...
Click to expand...
Why would diamonds do it and not have it happen to carbides in general? It certainly does not seem that way based on the cutting done with high alloy steels. Alvin Johnson for example has compared 1095 and M2 blades at near idential hardness (66 for 1095 and 65 for M2), and M2 gets *much* better edge retention than 1095 on abrasive media, and the performance is consisently ahead. He doesn't use diamonds though, actually uses a variety of ceramic and natural hones.

..as a result at the begining edge is same as for simple carbon steel and after it wear out carbide teeth came out and start cutting - like postponed secondry sharpness."
Click to expand...
The wear resistance of the carbides isn't the dominant factor in many types of blunting and even if fresh carbides were exposed on a worn edge it would not induce a significant gain in sharpness because the edge has been rolled and thickened. The actual cutting ability of carbides is pretty much insignificant as they are very small compared to the teeth left by even a moderate rough finish. Roman has already micro-graphed edges with steels with large carbides and they are clearly present in the edge, not ripped out.

-Cliff
 
Diamonds are harder than carbides and will thus cut the carbides just as they cut the matrix.
 
Cliff Stamp said:
Roman has already micro-graphed edges with steels with large carbides and they are clearly present in the edge, not ripped out.
Click to expand...

Is it present on the web? Pictures, etc.

Thanks, Vassili.
 
Cliff, wouldn't the act of sharpening the bevel on a worn edge straighten out the edge where it rolled and blunted while at the same time expose fresh carbides?

I don't follow how you could expose fresh carbides with a sharpener without doing some roll correction and edge straighening by taking out the blunt areas at the same time.
 
mete said:
Diamonds are harder than carbides and will thus cut the carbides just as they cut the matrix.
Click to expand...

On this I have replay like diamonds looks like sharp nidles and like spear take carbides out.

Thanks, Vassili.
 
Vassili I don't doubt for a minute that the carbide get knocked out by diamonds to some degree but the carbides are so small and so numerous I doubt it is significant enough to make note of.

I guess I have trouble seeing how a diamond will grab anymore carbides than an old style carborundum sharpening wheel or oil stone would.
 
I am talking about 6, 3 and 1 micron diamond powder - 3000, 8000 and 14000 mesh. Also I have now 50000 and 100000 mesh which is probably 0.3 and 0.15 micron.

I use it on leather:

stones-06.jpg


Thansk, Vassili.
 
This is pretty easy to test, try some cutting and see what happens. I have done it with fine and x-coarse DMT, I don't see either of the effects in the above. I thought Roman had posted such a picture but I could not turn it up, I emailed him.

STR said:
Cliff, wouldn't the act of sharpening the bevel on a worn edge straighten out the edge where it rolled and blunted while at the same time expose fresh carbides?
Click to expand...
Sure, but the arguement was that this would happen in use, not sharpening. Now you can actually see blades take an increase in sharpness after extended use, but it isn't due to exposure of new carbides, the actual edge degrades, the damage is *way* bigger than carbides and can readily be seen under 10x mag, I talked about it a few years ago and called it self-sharpening.

It is kind of funny because really low end steels can start to pull ahead of better ones if you use them until they become really dull and the cheap ones break apart and start to get some slicing action back while the fine grained and high quality ones will just wear smooth. I talked about this in a thread called something like cheaper steels = better performance.

I don't consider it to be of functional benefit because the sharpness of the blades at his point is *really* low and I would long have sharpened them. It is an interesting aside and did lend some credibility to the often argued high cutting ability and edge retention of damascus with highly contrasted materials which I am fairly curious about, for anyone so interested this was discussed on Swordforums.

mete said:
Diamonds are harder than carbides and will thus cut the carbides just as they cut the matrix.
Click to expand...
It is more complicated than that. You would need to prove that the force required for the diamonds to cut the carbides doesn't exceed the forces which bind the carbides in the steel. Even if the force ratio drastically favors the binding force, there is still a minimal amount of carbide/matrix contact which will allow the necessary force fraction. It is also possible that softer abrasives which are sharper in structure could actually lower the required force and thus cut carbides which harder abrasives would pull out. However if anything, it would seem to me based on pictures I have seen of Diamonds that they would be superior to other carbides in this respect as they look sharper.

-Cliff
 
I am cutting oak piece 60 dgree to fiber:

Before cutting right after 1 micron diamond Test 0
30.0 40.0 40.0 40.0 40.0 40.0 40.0 40.0 40.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 60.0 60.0 60.0 60.0 60.0 70.0 70.0 70.0 70.0
Mean = 51.0
95% confidence interval for Mean: 47.13 thru 54.87
Standard Deviation = 10.6 High = 70.0 Low = 30.0
Median = 50.0
Average Absolute Deviation from Median = 7.67

After 1st cm cut out Test 1
50.0 70.0 70.0 70.0 80.0 80.0 80.0 80.0 80.0 80.0 80.0 80.0 80.0 90.0 90.0 90.0 90.0 90.0 90.0 90.0 100. 110. 110. 110. 110. 120. 120. 120. 130. 150.
Mean = 93.0
95% confidence interval for Mean: 85.32 thru 100.7
Standard Deviation = 21.2
High = 150. Low = 50.0
Median = 90.0
Average Absolute Deviation from Median = 15.7

Test 2 (2cm)
60.0 80.0 80.0 80.0 80.0 80.0 80.0 80.0 80.0 90.0 90.0 90.0 90.0 100. 100. 100. 100. 100. 100. 100. 110. 110. 110. 110. 120. 120. 130. 130. 130. 140.
Mean = 99.0
95% confidence interval for Mean: 92.25 thru 105.8
Standard Deviation = 19.2
High = 140. Low = 60.0
Median = 100.
Average Absolute Deviation from Median = 15.0

Test 3 (3cm)
50.0 60.0 70.0 80.0 80.0 80.0 80.0 80.0 80.0 80.0 80.0 90.0 90.0 90.0 90.0 90.0 100. 100. 100. 100. 100. 110. 110. 110. 110. 120. 120. 120. 130. 130.
Mean = 94.3
95% confidence interval for Mean: 87.58 thru 101.1
Standard Deviation = 19.6
High = 130. Low = 50.0
Median = 90.0
Average Absolute Deviation from Median = 15.7

Test 4 (4cm)
60.0 60.0 70.0 80.0 80.0 80.0 80.0 90.0 90.0 90.0 90.0 90.0 90.0 90.0 90.0 90.0 90.0 100. 100. 100. 100. 100. 100. 110. 110. 110. 110. 120. 130. 130.
Mean = 94.3
95% confidence interval for Mean: 87.58 thru 101.1
Standard Deviation = 17.0
High = 130. Low = 60.0
Median = 90.0
Average Absolute Deviation from Median = 12.3

Test 5
80.0 80.0 80.0 90.0 90.0 90.0 100. 100. 100. 100. 100. 110. 110. 110. 110. 120. 120. 120. 120. 120. 120. 130. 130. 130. 130. 130. 130. 130. 140. 140.
Mean = 112.
95% confidence interval for Mean: 104.5 thru 119.5
Standard Deviation = 18.1
High = 140. Low = 80.0
Median = 115.
Average Absolute Deviation from Median = 15.3

Test 6
70.0 80.0 90.0 90.0 90.0 90.0 100. 100. 100. 100. 100. 100. 110. 110. 110. 110. 120. 120. 120. 120. 120. 130. 130. 130. 130. 130. 140. 140. 140. 150.
Mean = 112.
95% confidence interval for Mean: 104.9 thru 119.8
Standard Deviation = 19.8
High = 150. Low = 70.0
Median = 110.
Average Absolute Deviation from Median = 16.3

Test 7
90.0 90.0 100. 100. 100. 100. 100. 110. 110. 120. 120. 120. 120. 120. 120. 120. 130. 130. 130. 130. 140. 140. 140. 140. 140. 150. 160. 160. 170. 180.
Mean = 126.
95% confidence interval for Mean: 118.5 thru 133.5
Standard Deviation = 23.1
High = 180. Low = 90.0
Median = 120.
Average Absolute Deviation from Median = 18.0

Test 8
70.0 90.0 90.0 90.0 90.0 100. 100. 100. 100. 100. 110. 110. 110. 110. 110. 120. 120. 120. 120. 120. 120. 120. 120. 120. 120. 130. 130. 150. 150. 180.
Mean = 114.
95% confidence interval for Mean: 106.5 thru 121.5
Standard Deviation = 21.3
High = 180. Low = 70.0
Median = 115.
Average Absolute Deviation from Median = 15.3

Test 9
100. 100. 110. 110. 120. 120. 120. 130. 130. 130. 130. 130. 130. 140. 140. 140. 140. 140. 140. 150. 150. 150. 160. 160. 160. 160. 160. 170. 180. 180.
Mean = 139.
95% confidence interval for Mean: 132.1 thru 146.5
Standard Deviation = 21.3
High = 180. Low = 100.
Median = 140.
Average Absolute Deviation from Median = 16.7

Test 10
90.0 90.0 90.0 90.0 90.0 100. 100. 100. 110. 110. 110. 110. 120. 120. 120. 120. 120. 120. 120. 120. 120. 130. 130. 130. 140. 140. 140. 150. 150. 160.
Mean = 118.
95% confidence interval for Mean: 111.3 thru 124.7
Standard Deviation = 19.4
High = 160. Low = 90.0
Median = 120.
Average Absolute Deviation from Median = 14.7

Test 11
70.0 80.0 90.0 90.0 100. 100. 100. 100. 100. 100. 100. 110. 110. 110. 120. 120. 120. 120. 120. 120. 130. 130. 130. 130. 130. 140. 140. 140. 140. 160.
Mean = 115.
95% confidence interval for Mean: 108.0 thru 122.0
Standard Deviation = 20.3
High = 160. Low = 70.0
Median = 120.
Average Absolute Deviation from Median = 16.3

Test 12
90.0 90.0 90.0 90.0 100. 100. 100. 100. 110. 110. 110. 120. 120. 120. 120. 130. 130. 130. 130. 130. 130. 130. 130. 140. 140. 140. 140. 150. 150. 170.

Mean = 121.
95% confidence interval for Mean: 114.1 thru 128.6
Standard Deviation = 20.5
High = 170. Low = 90.0
Median = 125.
Average Absolute Deviation from Median = 16.7

Test 13
80.0 100. 100. 100. 110. 110. 110. 110. 110. 110. 120. 120. 120. 120. 120. 120. 120. 130. 130. 130. 130. 130. 130. 130. 140. 140. 140. 150. 150. 170.
Mean = 123.
95% confidence interval for Mean: 115.5 thru 129.8
Standard Deviation = 18.0
High = 170. Low = 80.0
Median = 120.
Average Absolute Deviation from Median = 13.3

Test 14
80.0 90.0 100. 100. 100. 110. 110. 110. 120. 120. 120. 120. 120. 120. 120. 130. 130. 130. 130. 130. 130. 130. 140. 150. 150. 160. 160. 160. 170. 170.
Mean = 127.
95% confidence interval for Mean: 119.5 thru 134.5
Standard Deviation = 22.9
High = 170. Low = 80.0
Median = 125.
Average Absolute Deviation from Median = 17.7

After first cut it shous big increase in dullness and then slightly dulling and after 14cm still cutting oak just perfectly. I notice that it cutting better after first 5 cm, before it was too sharp and penetrates into wood too much making cut kind of nervious, but now it is smoose and enjoible.

Thanks, Vassili.

P.S. This is the knife - bulat by Kirpichev:

knife74-04.jpg
 
Hi Vassili,
That seems strange!
I don't think diamonds spear anything, they have a cubic crystal structure not long pointed spears and break into blocky chunks like sand or salt. They are harder than carbides so they will scratch and sharpen the carbides. Normal iron and chrome carbides are softer than any of these common abrasives:
black SiC has a hardness of 2500 knoop.
green SiC is 2600
boron carbide (Norbide) is 2800 (blocky angular grain shape)
Cubic boron nitride (borazon/CBN) is about 4000
Diamond is about 8000

I think vanadium carbides are up there around green SiC but softer than boron carbide, CBN or diamond (mentioned because you have been playing with high vanadium steels)

Now, diamond is not recommended for grinding iron alloys because, being pure carbon, they will dissolve in steel (changing its carbon content on the surface), change to graphite, carbon dioxide etc. even under water. I don't think hand lapping will generate enough heat to do this if you use diamond lubricant or water. If you are dry grinding with diamond then maybe you are changing the steel on a microscopic scale?

If you are knocking your carbides out, it is probably because they are large and your angle is too low for the steel to hold them in well. Roman Landes posted a nice PDF chart showing carbide sizes in some steels over on the testing forum. http://www.schmiedecafe.com/forum/attachment.php?attachmentid=83 that helped you figure out what the best sharpening angle was for the steels in the pictures.
 
Vasilli's original post.

"Diamond sharpening rip off carbides from steel and sharpen just steel matrix, as a result at the begining edge is same as for simple carbon steel and after it wear out carbide teeth came out and start cutting - like postponed secondry sharpness."

I didn't catch that the original argument was that this would happen in use. I read sharpening above. But I see now where you are referring to in his statement. Sorry Vassili it went right by me. Obviously Cliff and the others didn't miss it though.
 
No, I dont, have problem as I understand, this is just theory I heard on Russian Forum - like diamonds may rip out carbides instead of sharpening them. I don't think so myself, but it will be good to have some proofe - like there is no holes in edge - marks of ripped of carbides. Cliff very well explain this - so it may happen on weak matrix.

Did you see something like this in your microskope or it is impossible to recognize carbides from matrix (I bet they are same color).

Thanks, Vassili.
 
The pictures in Roman's PDF are taken at 1,000 power, I think. I can only make my microscope go up to 120 power so I don't think I could see carbides unless they were very large.
 
nozh2002 said:
I am cutting oak piece 60 dgree to fiber
Click to expand...
I don't understand exactly what this means? You are carving wood? What does the cm refer to, depth of wood carved?

After first cut it shous big increase in dullness and then slightly dulling ...
Click to expand...
Blunting is highly nonlinear, this is the expected behavior, to see continuous increases in edge loss you have to keep doubling the amount of work done.

For example, look at the edge retention with the modifed profile and rough belt finish in the following :

http://www.physics.mun.ca/~sstamp/knives/becker_cu_7.html

Note the extent of blunting in the last 254 cuts is approximately the same as in the first two cuts.

This has nothing to do with carbides, but is because as steel deforms it takes more force to make it deform more and similar with wear, thus edge loss is nonlinear.

You also want to repeat the trials at least three times and average the results to smooth them out a little and make sure you don't get excited about a non-real peak.

You have a spike in the middle for example at 132-146 which I would bet isn't meaningful.If you extended the CI's this would be eliminated, right now they only cover 1/20, so you had a decent chance to see an outlier past them in your work due to the sample size.

Nice work.

-Cliff
 
This is old picture, now I am using same wood, but I am cutting not perpendiculare to fiber - 60 dgree instead.

knife73-12.jpg


I am wittling it by 1cm and test edge.

Thanks, Vassili.
 
So all the wood in a 1 cm section is carved/whittled away in small chips like those shown there. This would take a large number of cuts correct?

-Cliff
 
Yes. I think this way for each cm I have statistically same load on the edge.

Thanks, Vassili.
 
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