bamboo skewers and vg10

T

Threethreethree

Joined
May 30, 2013
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117
Hello there

I was carving a bamboo skewer to pick lint off a few knives when a noticed a burr forming readily right after maybe 4 very low angled, low stress cuts.
This knife is a delica wave that i partially convexed to zero grind then applied a higher curvature as the edge was way too fragile and maintenance was freaking high. i guess the very edge is prolly close to 30 deg incl. finished on ceramic deburred using a coticule then a few passes on a 3 microns diapaste on balsa.
This edge is perfectly durable when carving briar with a twisted grain pattern to the point i can carve for about 2-3 hours with only a very low percepted loss of sharpness ( loss of treetopping ability yet still able to grab hairs readily well over the skin.)
Whats going on with bamboo then, it doesnt feel to be hard on the edge AT ALL yet it can destroy my fine edge in about 2 mins of fine whittling ? I'm stumped.
 
Bamboo is very hard but your sharpening routine is a bit abstract which will cause random failures and unpredictability in performance.
 
Briar burl is much much harder than those little skewers, which is really soft bamboo.
How is my sharpening routine abstract ? I get great performance for general use... the only issue i have is with a tiny SOFT bamboo without its bark.
Keep in mind this is a flat saber delica, even if convexed and thinned it is still much more thicker than its ffg counterpart so no my edge isnt paper thin.
 
Again, bamboo is very hard and will beat the snot out of most any edge. I tell you this from experience.

Your sharpening starts with a synthetic, moves to a natural, and finishes with a synthetic compound. The use of the natural stone is fine but following it with a synthetic compound alters the natural finish which has altered the ceramic stone finish. That's not even to mention the vast grit levels possible when using a coticule so, depending on the slurry and grade of the stone it could be coarser than your ceramic or finer than your diamond compound. This is why I say your method is abstract.
 
Threethreethree said:
finished on ceramic deburred using a coticule then a few passes on a 3 microns diapaste on balsa.
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Are you using a spyderco type ceramic or a shapton type ceramic? How long have you has the knife and what is the coarsest stone you have sharpened on?

Jason has a point about your sharpening routine. "finished" implies you deburred, so it's hard to tell what you are doing on the coticule (garnet for a vg10 steel?) then again on the diamond abrasive after the ceramic stone. Finer and harder ceramics like spyderco don't remove a lot of material and can start to stress an edge when trying to remove too much material. The coticule is a natural water stone so there are some compounding problems there. Consistency of the stone, water to mud ratios, flatness (especially after a 'true' flat ceramic), natural abrasive with a higher carbide steel and things i know i'm forgetting. Is the balsa strop well used? How long have you been using it? Adding new paste will keep fresh abrasive on the strop but it won't remove old abrasive or old swarf which can stress an edge by not cutting into the steel properly and just burnishing. Now these things may or may not be what Jason was thinking about and he may or may not agree with them, but with out knowing more these are good starter points to try removing/ moving around to see what is the culprit. My money is on an over stressed edge.
 
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Bamboo fiber contains silica, so it might be harder on your edge than you would think.
 
For nominal/average bamboo. Skewer probably young bamboo so #s are lower. While black/aged bamboo janka will be in 2K+ and EM reach 4Mil.
http://www.wood-database.com/lumber-identification/monocots/bamboo/

Just to test, I whittled black/age bamboo with aebl-62rc, 14c28n-62rc, 52100 63&64rc, s110v 63rc, D2 63rc 4-5" knives -> tada all suffered some kind of edge damage (mostly rolled). While choppers (52100 8.5" 56rc 15dps, cruV 54rc 15dps, 80crv2 58rc 13dps) edges laugh at bamboo.

Keep in mind that whittle long fiberous material with high Elastic Modulus will put high lateral stress on an edge. hence warrant steel/blade with high toughness for this type of work/task.
 
Bluntcut's posts are always very chocked full of information. Read carefully, as he doesn't use a lot of words, but he has a lot of good information to share and seems to have done quite a bit of testing in preparation for this post. Good job Bluntcut! As usual, I learned something.

Brian.
 
I also did some testing with about every steels i own and i also noticed some damage within 3-5 cuts in s90v, s30v, cpm m4, 1095.
Vg10 suffered consistantly the most damage ( 1095 burred too but way less but the edge is thicker prolly around 36 degrees, none of the other steels i tested burred even when raising the cut angle in the skewer.
Cpm m4 suffered the least damage.
Regarding my sharpening method...
240 sic convex zero then medium rod freehand , the rod was kept very clean during the process to avoid burnishing and avoid excessive burring, white ceramic rod, kept clean the same way, getting rid of the med rod scratch pattern.
Coticule with no slurry just water for 5 passes per side (this is a very small coticule, 10 or 12 cm lenght).
Lastly if i use balsa that's to keep it clean and avoid burnishing over swarf, balsa was used very cautiously as the edge was very clean from the coticule but still not capable of treetopping so 5 or 10 passes per side nothing more.

If the edge was so crappy how would i be capable of whittling briar burl for so long ?
I'm finally admitting bambo is nasty to cut after seeing how i can see damage within 3 cuts under bright light with cpm m4 and a 40 deg microbevel but still i feel shocked as nothing indicates it is so rough on the edges when compared to carving zytel or such where you can definitely hear the grinding going on.

Edit: Talking about flatness... none of my ceramic rods are flat, they got ridges that load up quickly and valleys that never blackens judging by the sheer number of youtube videos i watched that pictured a dirty sharpmaker, i can tell you most of the rods just AREN'T flat, as a matter of fact my coticule is.
 
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Quoted from the 'workability' section in the wood-database link provided in Bluntcut's post (:thumbup:), I think this sums it up very well:

"Also, bamboo is very high in silica—from .5% to 4.0%, found almost entirely in the outermost layers of the stem—so care must be taken when processing lumber. Carbide cutters are strongly recommended, and surface sanding is suggested instead of thickness planing with steel cutters, both for longevity of cutting edges, and quality of the finished surface. Bamboo glues, stains, and finishes well. When turning giant bamboo species, tools dull quickly"
Click to expand...

Aside from the above, Spyderco's VG-10 burrs or rolls easily anyway, even as compared to VG-10 from other makers who take it a little higher in hardness. I think that's my biggest pet peeve with Spyderco's VG-10 blades.


David
 
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