why is my s90v blade sensitive to microbevel angle?

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BruceMack

Joined
May 20, 2015
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My s90v blade is sharper with a 20° microbevel than with a 15° microbevel. The blade has been reprofiled to a primary bevel slightly greater than 13° on a KME with diamond stone sequence to 1500 grit. The angle was measured with the inclinometer app. of my phone. The brown rod of the Sharpmaker leaves a visible shiny microbevel at the very edge, validating the appropriate acuteness of the primary bevel. I have resharpened several times with the medium - fine - extra-fine rod sequence and have drawn the edge lightly along a block of hardwood to remove trace wire edge if any. The edge feels smooth to touch. However, compared to blades of CPM-154, s30v, s35vn, and M390 the edge is rough when cutting my favorite test medium, 110-pound weight card stock. It seems to snag and does not have the masterful progression (only a knife addict could say this) of the other blades.
However, after I change the microbevel to 20° the blade becomes wonderfully sharp as I would expect from the thin stock and the thickness behind the edge. I'm pleased with the result but wonder why this is happening. I'd appreciate your opinions.
 
It may be greater than 13 degree and close to 15 and therefore deburring at 15 degree might have not worked sufficiently.
My 2 cents.
 
BruceMack said:
Sharpmaker
Click to expand...
Yah . . . you might consider skipping the Sharpmaker and just finish and debur on the KME.

The reason I say this is the Sharpmaker has been known to be less accurate angle wise then a true sharpening jig. I only know what I have read and seen demonstrated in YouTube channels that I respect for other sharpening topics. The Rods can be bowed not to mention holding the knife in hand rather than on a rigid jig surface / clamp. Also are you getting the same rod on the same side each time; lets say one is slightly bowed and the other is straight or curved the other direction.

After saying that I feel like there may be a facet to your combined method that I'm not fully getting even though you have been very clear. My problem; not your post.

Personally I would MUCH rather use a 15° sharpening bevel than a 20°. I hope you get this one sorted out. I'll be interested to hear how it turns out.
 
The Sharpmaker's ceramics won't do much (anything, really) to improve or refine the S90V edge coming off the diamond. There's a LOT of vanadium carbide in S90V, and the diamond will do a much better job finishing it off, whereas the ceramics will be more likely to only burnish the carbides or force them out of the edge, leaving gaps where the carbides used to be, therefore leaving it weaker and rough.

It's also unlikely that S90V will leave much of a burr or wire, for the same reasons. Very high-carbide steels at decent hardness generally don't burr that much anyway. And diamond will cut it much more cleanly at a light touch, which further reduces the likelihood of significant burring issues. Finish on the diamond and leave it at that. You should be able to get good results with a microbevel using the diamond only, regardless of what the microbevel angle is.
 
I like the above suggestions better than what I could come up with. The blade geometry/KME interaction does not permit a more acute primary bevel as the clamp gets in the way. I can’t be sure it is sufficiently acute for the chosen 15 degree microbevel. I haven’t been able to acquire good freehand sharpening skill so I depend on the Sharpmaker for the final edge. I’ve been pleased with the result. Luckily in this case the 20 degree microbevel is minute and seems not to result in more slicing effort.
 
Obsessed with Edges said:
The Sharpmaker's ceramics won't do much (anything, really) to improve or refine the S90V edge coming off the diamond. There's a LOT of vanadium carbide in S90V, and the diamond will do a much better job finishing it off, whereas the ceramics will be more likely to only burnish the carbides or force them out of the edge, leaving gaps where the carbides used to be, therefore leaving it weaker and rough.

It's also unlikely that S90V will leave much of a burr or wire, for the same reasons. Very high-carbide steels at decent hardness generally don't burr that much anyway. And diamond will cut it much more cleanly at a light touch, which further reduces the likelihood of significant burring issues. Finish on the diamond and leave it at that. You should be able to get good results with a microbevel using the diamond only, regardless of what the microbevel angle is.
Click to expand...
The 1500 grit edge certainly was sharp. The attempted refinement with the ceramic may not have altered working sharpness but did seem to smoothen (gr?) the cut.
 
BruceMack said:
The 1500 grit edge certainly was sharp. The attempted refinement with the ceramic may not have altered working sharpness but did seem to smoothen (gr?) the cut.
Click to expand...

If you're wanting a smoother, more polished cut with S90V, I'd suggest using a diamond compound on a hard strop of wood (like basswood, maple, etc). For the reasons I mentioned earlier, the diamond will more cleanly polish & shape everything at the edge, including the hard carbides. That'll leave the edge stronger while also making sure it's as sharp as it can possibly be. Diamond compounds at 3-micron and finer will follow the 1500 diamond hone very well. I've liked DMT's 3-micron Dia-Paste compound, as it polishes these steels very, very quickly (used on wood) following an EF or finer hone, while also leaving the apex very keen & sharp.
 
I think I have it in the woodshop from my plane sharpening days. It's on my agenda. Thanks!
 
Hi,
Two ideas, carbide volume and sharpening procedure

0) high carbide volume is high
See whats-the-lowest-functionable-angle-by-steel-type.1587190/#post-18129004
Metallurgist Roman Landes says, if carbide volume is greater than 15%, to both take and hold a high polished sharpness, you need 20-30 degrees per side.

S90V is S90V
20CV is M390
K390 is essentially 10V/Vanadis8, sharpening procedure overcomes grindability issues
Code: 
20CV            TCC ( 164 mm) = -157 + 15.8*Hardness (Rc) – 17.8*EdgeAngle(°) + 11.2*CrC(   0) + 14.6*CrVC(  17) + 26.2*MC(   2) + 9.5*M6C(   0) + 20.9*MN(   0) + 19.4*CrN(   0) + 5*Fe3C(   0)
Vanadis 8       TCC ( 236 mm) = -157 + 15.8*Hardness (Rc) – 17.8*EdgeAngle(°) + 11.2*CrC(   0) + 14.6*CrVC(   0) + 26.2*MC(  15) + 9.5*M6C(   0) + 20.9*MN(   0) + 19.4*CrN(   0) + 5*Fe3C(   0)
S90V            TCC ( 268 mm) = -157 + 15.8*Hardness (Rc) – 17.8*EdgeAngle(°) + 11.2*CrC(   0) + 14.6*CrVC(  13) + 26.2*MC(   9) + 9.5*M6C(   0) + 20.9*MN(   0) + 19.4*CrN(   0) + 5*Fe3C(   0)
10V             TCC ( 301 mm) = -157 + 15.8*Hardness (Rc) – 17.8*EdgeAngle(°) + 11.2*CrC(   0) + 14.6*CrVC(   0) + 26.2*MC(  17) + 9.5*M6C(   0) + 20.9*MN(   0) + 19.4*CrN(   0) + 5*Fe3C(   0)

20CV           Fe3C 0 CrC    0 CrVC 17.5 MC  2.5 M6C   0 MN  0 CrN 0
Vanadis 8      Fe3C 0 CrC    0 CrVC    0 MC   15 M6C   0 MN  0 CrN 0
S90V           Fe3C 0 CrC    0 CrVC   13 MC    9 M6C   0 MN  0 CrN 0
10V            Fe3C 0 CrC    0 CrVC    0 MC 17.5 M6C   0 MN  0 CrN 0

20CV           TCC 164   Volume   20%  Landes   20-30°dps
Vanadis 8      TCC 236   Volume   15%  Landes 12.5-20°dps
S90V           TCC 268   Volume   22%  Landes   20-30°dps
10V            TCC 301   Volume 17.5%  Landes   20-30°dps


See
https://knifesteelnerds.com/2018/11/19/steel-edge-retention/
https://knifesteelnerds.com/2018/11/26/steel-edge-retention2/
...

Another comparison is between Crucible 10V, Bohler K390, and Uddeholm Vanadis 8.
Each has a somewhat different composition to achieve the same thing – 15-18% vanadium carbide volume.


M390 is 20CV

Knife Sharpening : 64 HRC k390 + Soft Arkansas - CliffStamp , Thats a 15-18% vanadium carbide steel
, sharpening procedure overcomes grindability issues



0) maybe you're "overworking" the apex
so change the way you prepare for microbevel
try deburring with diamonds and double angle before spyderco not with wood
are you using lube and light force? How many passes to microbevel with spyderco?
See Spyderco Ultra Fine - problems with Vandium steels?

Also, try 20-3 = 17 degrees on the sharpmaker by shimming with a rod
from Tilting the sharpmaker - Spyderco Forums
IMG_19671.jpg

IMG_19651.jpg
 
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