Mule Team 24

[Bodog]

Here's a good discussion though what's referred to as rare seems to be more common than intimated in the thread.

http://www.bladeforums.com/forums/showt ... em+carbide

[Steel_Drake]

Cross-posted from BF because it is relevant to this thread, and also doubles as a test of the apex strength of the Maxamet Mule at ~15-16 dps with no microbevel:

http://www.youtube.com/watch?v=gDB0q1QffOc

I decided to begin empirically testing whether the theoretical inability of aluminium oxide or silicon carbide abrasives to shape vanadium carbides resulted in an inferior initial sharpness, apex strength, or high sharpness edge retention by testing the worst case scenario first.

I'd been polishing the edge bevels on my Maxamet Mule on a series of high grit waterstones in order to be able to capture some USB microscope images of the scratch patterns left by those stones and wound up with the Mule with an edge bevel finished at 13,000 grit on my Sigma Power Select II 13,000 stone (which I will again note is AlOx with a binder unlike the SiC stones with almost no binder in the same line).

I figured that if any sequence of two stones would maximize the likelihood of both failing to abrade the vanadium carbides and undercutting the support for those carbides on the apex line by abrading the metal matrix around the carbides, it would be an ultra high grit AlOx waterstone used with a thick slurry (to maximize the chance of undercutting the support for the carbides on the apex line) and then to use a Spyderco solid sintered alumina ceramic UF benchston which should be even worse in terms of inability to abrade vanadium and also should have a high risk of burnishing the apex and thus weakening it by plastic deformation.

If any sequence of two stones should produce an apex prone to carbide tear out and premature loss of sharpness it should be these two stones used back to back.

Once the sharpening and deburring (using high angle passes) were completed, I checked that the initial sharpness was at the expected level of easily being able to do crossgrain pushcuts on newsprint and still being able to slice paper towel (though the expected slicing aggression would be extremely low at this level of polish).

Next, I made several cuts into pine to test apex strength. This testing procedure to check for apex strength was sourced directly from proponents of the idea that AlOx and SiC abrasives should not be used on high hardness, high vanadium steels. I then re-checked the pushcutting sharpness to test for any lack of apex strength. I found no loss of pushcutting sharpness. I continued to make cuts into the pine until I'd reached dozens and dozens of cuts and still found no significant loss of pushcutting sharpness.

Finally, immediately after the pine cutting test I continued on to test high sharpness edge retention by making a couple dozen strips of cardboard across the corrugations and found the Maxamet Mule still somewhat able to make crossgrain pushcuts on newsprint with many parts of the apex, a performance indicating no dramatic loss of high sharpness.

In summary, this empirical test found absolutely zero evidence of any empirically detectable reduction in initial sharpness, apex strength, or high sharpness edge retention from sharpening high hardness, high vanadium content steel on extremely fine aluminium oxide abrasives. In light of this being a near worst case scenario for trying to provoke any negative consequences from using AlOx or SiC abrasives on these types of steels, I'm not sure that anything more would be learned by repeating the experiment with stones in the ~4000 JIS grit range.

[Bodog]

Cross-posted from BF because it is relevant to this thread, and also doubles as a test of the apex strength of the Maxamet Mule at ~15-16 dps with no microbevel:

http://www.youtube.com/watch?v=gDB0q1QffOc

I decided to begin empirically testing whether the theoretical inability of aluminium oxide or silicon carbide abrasives to shape vanadium carbides resulted in an inferior initial sharpness, apex strength, or high sharpness edge retention by testing the worst case scenario first.

I'd been polishing the edge bevels on my Maxamet Mule on a series of high grit waterstones in order to be able to capture some USB microscope images of the scratch patterns left by those stones and wound up with the Mule with an edge bevel finished at 13,000 grit on my Sigma Power Select II 13,000 stone (which I will again note is AlOx with a binder unlike the SiC stones with almost no binder in the same line).

I figured that if any sequence of two stones would maximize the likelihood of both failing to abrade the vanadium carbides and undercutting the support for those carbides on the apex line by abrading the metal matrix around the carbides, it would be an ultra high grit AlOx waterstone used with a thick slurry (to maximize the chance of undercutting the support for the carbides on the apex line) and then to use a Spyderco solid sintered alumina ceramic UF benchston which should be even worse in terms of inability to abrade vanadium and also should have a high risk of burnishing the apex and thus weakening it by plastic deformation.

If any sequence of two stones should produce an apex prone to carbide tear out and premature loss of sharpness it should be these two stones used back to back.

Once the sharpening and deburring (using high angle passes) were completed, I checked that the initial sharpness was at the expected level of easily being able to do crossgrain pushcuts on newsprint and still being able to slice paper towel (though the expected slicing aggression would be extremely low at this level of polish).

Next, I made several cuts into pine to test apex strength. This testing procedure to check for apex strength was sourced directly from proponents of the idea that AlOx and SiC abrasives should not be used on high hardness, high vanadium steels. I then re-checked the pushcutting sharpness to test for any lack of apex strength. I found no loss of pushcutting sharpness. I continued to make cuts into the pine until I'd reached dozens and dozens of cuts and still found no significant loss of pushcutting sharpness.

Finally, immediately after the pine cutting test I continued on to test high sharpness edge retention by making a couple dozen strips of cardboard across the corrugations and found the Maxamet Mule still somewhat able to make crossgrain pushcuts on newsprint with many parts of the apex, a performance indicating no dramatic loss of high sharpness.

In summary, this empirical test found absolutely zero evidence of any empirically detectable reduction in initial sharpness, apex strength, or high sharpness edge retention from sharpening high hardness, high vanadium content steel on extremely fine aluminium oxide abrasives. In light of this being a near worst case scenario for trying to provoke any negative consequences from using AlOx or SiC abrasives on these types of steels, I'm not sure that anything more would be learned by repeating the experiment with stones in the ~4000 JIS grit range.

I'm still wondering if the majority of the carbide volume in a steel like Maxamet is primarily chromium and tungsten.

I would like to see a test like this performed on a steel like 15V or with rex 121 where there's more carbon and less chromium. Tests with SEM images both before and after and then repeated with CBN and then polycrystalline and mono crystalline diamonds.

[Bodog]

I guess in just curious about how much chromium gets in the way of other carbide formers. What would the difference be if there were zero chromium.

[Steel_Drake]

I'm still wondering if the majority of the carbide volume in a steel like Maxamet is primarily chromium and tungsten.

I would like to see a test like this performed on a steel like 15V or with rex 121 where there's more carbon and less chromium. Tests with SEM images both before and after and then repeated with CBN and then polycrystalline and mono crystalline diamonds.

I specifically asked the proponents of the theory that AlOx and SiC shouldn't be used on high hardness, high carbide volume steels whether Maxamet @ 68 HRC would qualify as an appropriate test steel for an effect they alleged was even present in CPM-M4 @ ~62 HRC, and they all agreed that it was.

Also, SEM images wouldn't necessarily clarify the issue that much. I haven't been arguing that AlOx or SiC abrasives can abrade vanadium, rather I've been arguing that to the extent its true that AlOx and SiC cannot shape vanadium and tend to wear the metal matrix around the vanadium carbides, the effects are not empirically detectable in terms of initial sharpness, apex strength, and high sharpness edge retention (which is to say noticeable in use of the knife). My test showed very clearly that any negative side effects of using very high grit AlOx abrasives on Maxamet were not detectable in the apex's performance afterwards.

[Steel_Drake]

Again crossposting from this ongoing discussion on BladeForums, here are a few more empirical tests of the initial sharpness, apex strength, and high sharpness edge retention of a Spyderco Mule Team in Maxamet after being sharpened on a variety of abrasives in the 3k-5k grit range.

These tests also show that, at ~0.015" at 1/32" behind the apex and ~15 degrees per side, the Maxamet mule had no issues whatsoever with a fair bit of pine whittling.

http://www.youtube.com/watch?v=IAGHa-DdQX8
http://www.youtube.com/watch?v=IxLwfyu0A3Y
http://www.youtube.com/watch?v=DD5cj1K1yGE
http://www.youtube.com/watch?v=rw9ieD6BNjs

[Steel_Drake]

These videos are also crossposted from the above linked ongoing discussion on BF.

Here I test the initial sharpness and apex stability of a Spyderco Mule Team in Maxamet after being finished on a DMT EEF and a Spyderco M.

These tests show that deliberately making very hard cuts into bamboo and deliberately twisting out of cuts into bamboo is best avoided, and succeeded in quickly inducing some level of microscopic apex chipping on both apexes. Surprisingly, the apex set on the DMT EEF failed much more quickly than the apex set on the Spyderco M.

As above, the MT was at ~0.015" at 1/32" behind the apex and ~15 degrees per side.

http://www.youtube.com/watch?v=GBgVQLc9R6g
http://www.youtube.com/watch?v=6FhWZsO3ef4

[Steel_Drake]

This video is a retest of the initial sharpness and apex stability of a Spyderco Mule Team in Maxamet after being finished on a DMT EEF by doing hard cutting on bamboo chopsticks:

http://www.youtube.com/watch?v=hQXQq1-H4cM

This retest was done to eliminate a possible cause of the outlier result of the first DMT EEF apex performing noticeably worse than the Spyderco M apex in bamboo chopstick cutting. It was asserted that the outlier result was caused because some convexing had occurred in the sharpening of the Spyderco M apex and thus had increased its effective apex angle to ~17.5 degrees, thus giving it a significant strength advantage over the ~15 dps DMT EEF apex.

To address those concerns, I deliberately convexed the apex in the DMT EEF retest to ~17.5 dps and repeated the test.

The results were as follows:

There was no noticeable difference in the initial sharpness obtained off either abrasive. Both apexes were able to cleanly and easily do crossgrain pushcuts on newsprint at all points along the apex.

There was no noticeable difference in the apex strength obtained off either abrasive. Both apexes suffered comparable amounts and extents of microscopic apex chipping after doing similar amounts of hard cutting into bamboo chopsticks.

This additional test therefore still failed to produce any evidence to support the hypothesis that any noticeable negative side effects are produced on high hardness, high vanadium content steels from being sharpened on aluminium oxide or silicon carbide abrasives.

This test also served to show that on the Spyderco Mule Team in Maxamet, apex angles of ~17 dps suffered multiple small microscopic apex chips when making multiple hard cuts into a bamboo chopstick and deliberately twisting out of cuts into a bamboo chopstick. By contrast, the Mule Team in Maxamet took no apex damage whatsoever from all the pine cutting I did in earlier videos at ~15 dps.