Apex Bevel Geometry cross-sectional

I would be interested to see the results. I really like this thread, but I'm not knowledgeable enough to add anything worthwhile to the discussion :)
 
mrdeus - thanks for the acknowledgement. I need clue to decide whether to continue or shut up.

Cutting & sharpening interactions are too complex to formalize or hand-wave. So to save ourselves from bore-to-death-theory, perhaps I should jump to the end and propose an edge geometry which theorized to excel at sisal/manila rope cutting. Setup:

knives Endura vg-10 (cat 7 ranked) & GB cpm-m4 (cat 2 ranked)

dulling material double up 0.5" sisal rope (cheaper than using 5/8"), so 0.39 sq in vs 0.31 sq in.

test materials 24# printer paper and newsprint

baselines start at a decent tp V 30* inclusive cutting edge, count cuts until no longer slice newsprint, then printpaper. Repeat 2 times.

proposed geometry start with clean newsprint slice (maybe tp too but not sure), count cuts until no longer slice newsprint, then printpaper. Repeat 2 times.

If performance of baselines within +- 20% of proposed geometry, then it's inline with Ankerson's steel ranking. Now, if proposed-geometry-vg10 is close or exceed baseline-cpm-m4 performance, then I will introduce a modify-baseline before getting to a meaningful interpretation+conclusion.

I just throw this out there for everyone to give thoughts/suggestions. If there are interests, I will purchase sisal rope from HF and shoot videos. hm... is this test really just a newb way to waste ppl time and a big chunk of mine?
 
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I made conjectures that sharpening use edge-lead produce less burr and provide higher certainty at achieving a sharp edge. VG-10 steel was chosen because it's known for very tough burr.

In my 30 minutes video, I loop through each abrasive material, each time the same knife is forced dull by cut into a rock. Test for sharpness and burr/wire-free edge by slice newsprint/catalog-paper.

Abrasive materials:
Aluminum oxide stone 120grit, waterstone 1K, ceramic stone medium, diamond stone F+E+EE, honing rod 1.2K, spine of a ceramic knife, ceramic coffee cup, red clay flower pot, w&d 1K SiC sandpaper, granite rock.

[video=youtube;TgumZxt3ws4]http://www.youtube.com/watch?v=TgumZxt3ws4&feature=youtu.be[/video]

Your feedback is appreciated.
 
Interesting to see your technique. I've tried the "fold over" thing, but I think I used much less pressure. Perhaps I was too careful :). From what I've read, straight razor guys use edge leading strokes on stones.

So this video was to demonstrate that you can use edge leading strokes on a variety of materials?
 
mrdeus said:
Interesting to see your technique. I've tried the "fold over" thing, but I think I used much less pressure. Perhaps I was too careful :). From what I've read, straight razor guys use edge leading strokes on stones.

So this video was to demonstrate that you can use edge leading strokes on a variety of materials?
Click to expand...

Thanks for watching...

Yes. I fold the rolled/burr/wire quite agressively (listen to the sound & wood shaving). Even at 3 micron level, I was quite rough actually. The idea of folding is to eliminate weak apex that can't handle the folding-pressure (aka edge roll). So for 0.25 or 0.1micron and somehow still has burr/wire, I fold more gently.

Those edges in video are free of burr/wire, that is an important point. 30 minutes video is too long&boring to watch but not really too long if one has to fix an rock-dulled edge - well, 10 in this case. The final edge would whittle wood for a few minutes and still push cut newsprint (OK, I just done that).

I use edge-leading for most of my sharpening and exclusive usage for sub-micron edges (straight razor, scalpel, tree-top hair). To achieve 200-300nm edge, I edge-lead onto a 100nm diamond surface where diamond particles are partially embedded onto substrate/binder <= note: edge-lead into a diamond film and compound charged leather/balsa strop will (most likely) damage them.
 
It was a very dense thread, but man I really enjoyed your theoretical approach to sharpening.
Thank you very much, I'll see the video when I can have a little time.
keep on going,
Mateo.
 
... One thing I notice is that edge trailing on a firm stone seems to make the apex less uniform than going edge leading. Other thing is that stropping (at least with an abrasive) even on a surface as firm as a single sheet of paper wrapped around a stone, results in a large increase in apex uniformity"

HH, I don't understand. What is the difference then between edge trailing on a stone and stropping (edge trailing) on a sheet of paper with abrasive on a stone. Why would that make a difference?

And, one more thing, HeavyHanded - it is really about time that you make a video!!
 
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bluntcut said:
Yes. I fold the rolled/burr/wire quite agressively (listen to the sound & wood shaving). Even at 3 micron level, I was quite rough actually. The idea of folding is to eliminate weak apex that can't handle the folding-pressure (aka edge roll). So for 0.25 or 0.1micron and somehow still has burr/wire, I fold more gently.
Click to expand...

I just tried this again with a "problem knife" that I wasn't completely satisfied with the edge on. First I reset the bevel with back-forth strokes. Then I folded the wire edge over and cut it off (edge leading only). I went a bit more gung ho this time :). I could feel the burr very clearly after the first fold. I folded the edge right and left a few times. The result was a nice aggressive edge that cut newsprint very cleanly. I just used a 1000 grit water stone. I'll finish it another day (it's getting late). Could be used as it is now. I took a few strokes on a strop afterwards and it cleaned it up a little more.

One thing I reflected on was that it must be important to keep the same angle that you used when sharpening when cutting the burr off if you're planning on progressing to a finer stone, so you don't create a microbevel on the coarser stone. I guess removing the wire edge is most important on the final stone, but how important is it on the earlier stones when progressing over, for example, three stones? Is it better to fold and cut it on each stone to avoid having it "ripped" off on the following stone?

PS. I hadn't seen or heard of this "folding" technique until you mentioned it. It's interesting to try different ways of sharpening to see what works for me.
 
awestib said:
... One thing I notice is that edge trailing on a firm stone seems to make the apex less uniform than going edge leading. Other thing is that stropping (at least with an abrasive) even on a surface as firm as a single sheet of paper wrapped around a stone, results in a large increase in apex uniformity"

HH, I don't understand. What is the difference then between edge trailing on a stone and stropping (edge trailing) on a sheet of paper with abrasive on a stone. Why would that make a difference?

And, one more thing, HeavyHanded - it is really about time that you make a video!!
Click to expand...


The difference between stropping on hardwood, newspaper wrapped around a stone, even a waterstone, and stropping on a hard vitreous stone or diamond plate is night and day. It doesn't seem so, but that tiny bit of particle mobility and ability to move up and down under pressure is what sets it apart. The abrasives can 'line up' under pressure, in effect they all work as a team (they also have back and forth mobility). It isn't until a solid stone reaches very fine particle sizes that it begins to work with the same uniformity, and even then it has no mobility in place.

This is an excellent resource linked by another member

http://bosq.home.xs4all.nl/info 20m/grinding_and_honing_part_1.pdf

Go to section 2 - difference between sanding, grinding, and lapping. The loaded strop acts as something of a cross between sanding and lapping, waterstones somewhere between lapping and grinding. IMHO in order for a stropping/edge trailing operation to work, the particles need some mobility. Grinding with an edge trailing motion will create the largest possible amount of unsupported burr remnants, edge trailing with a loose slurry produces the least. I don't pretend to know what's going on at the apex re abrasives with varying mobility and under pressure from a variety of backings, trying to explain leaves me 'hands waving' as Bluncut would say. I do know if I whip up the most burr free edge I can off a hard stone and then backhone a few times I'll see a burr where there wasn't one, or a larger burr where there was a small one. Note - I do not consider a waterstone to be a 'hard' stone.

We just moved, as soon as I get a few rooms painted, maybe the wife will let me use her camera to do a video :) maybe she'll even set it up for me. The instant I get off the clock I revert to complete Luddite.
 
mrdeus said:
I guess removing the wire edge is most important on the final stone, but how important is it on the earlier stones when progressing over, for example, three stones? Is it better to fold and cut it on each stone to avoid having it "ripped" off on the following stone?
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Most of the time I fold at the final stone or 3microns whichever is larger. It's better to have a clean apex when progressing throught sub 3microns abrasives. Edge-leading burr/wire usually small so I don't worry about rip/gash/dig at the next finer stone. Now aday, I use edge-leading all the way down to 0.1micron abrasive and ONLY shaving edges get strop on bare horsebutt leather.

To be clear, I use both edge lead & trail stroke for edge reprofile + major grind + convex + polish.

"folding" is an old technique that everybody use to break off dangle/weak parts but that takes much more effort until the material is fatique and then fall off. Well, my impatience insisted that I cut the folded part off :)
 
Sometime I lulled into thinking that abrupt bevel shoulder transition is 'the' wedge and exactly where excess energy spent to thrush the blade forward in order for the apex to seperate matters. At the same time, I sing 'thin-behind-the-edge' song. So how high up in the blade the 'thin' should be?

Mora Classic, blade thickness ~2.2mm, striped painted with permanent marker.
morawedge20130120.jpg

Resistance/friction of contact areas erased marker from apex to the wedging-line where the blade is about 1.5mm thick.

hm, for cardboard (and perhaps other stiff materials) it seems that answer is the blade (usually at the spine) should be as thin as feasible, i.e. without compromise the blade integrity. Performance drop drastically as blade thickness increases.

My Opinel #9 easily out-cut this Mora, however the Mora's handle is more comfortable. I think a blade with 0.5-1mm thickness would excel on most indoor tasks.
 
I'm very loosely following all of this (I am learning and thinking about a lot of things, but feel I am not getting everything), but what about sharpening an edge inline? As in, moving the edge in a parallel motion sideways. I know this will prove to be harder on a waterstone due to wear, but an oilstone would work so long as you keep changing where you stroke. Also, I have machinist's handbooks available, so just shoot me a pm or post up here any questions you feel the book may have answers for.

Very good thread,
Connor
 
bluntcut said:
Sometime I lulled into thinking that abrupt bevel shoulder transition is 'the' wedge and exactly where excess energy spent to thrush the blade forward in order for the apex to seperate matters. At the same time, I sing 'thin-behind-the-edge' song. So how high up in the blade the 'thin' should be?

Mora Classic, blade thickness ~2.2mm, striped painted with permanent marker.
morawedge20130120.jpg

Resistance/friction of contact areas erased marker from apex to the wedging-line where the blade is about 1.5mm thick.

hm, for cardboard (and perhaps other stiff materials) it seems that answer is the blade (usually at the spine) should be as thin as feasible, i.e. without compromise the blade integrity. Performance drop drastically as blade thickness increases.

My Opinel #9 easily out-cut this Mora, however the Mora's handle is more comfortable. I think a blade with 0.5-1mm thickness would excel on most indoor tasks.
Click to expand...

I'm curious if you noticed any trends in the post testing blade strategies - did the greater wedging action of the Scandi 'protect' the cutting edge at all, or conversely did the decreased resistance overall allow the full convex to maintain apex geometry longer? There may be other benefits/penalties that are not immediately evident?

I have no theories re this, and have not done this test on my own.

HH

PS, your stripe pattern is similar to the one I used to apply when sharpening full convex on a hard stone - Sharpie only. I've gotten enough of a feel that I do it by looking at the grind pattern, but was a big help when I first gave it a try.
 
ConBon said:
I'm very loosely following all of this (I am learning and thinking about a lot of things, but feel I am not getting everything), but what about sharpening an edge inline? As in, moving the edge in a parallel motion sideways. I know this will prove to be harder on a waterstone due to wear, but an oilstone would work so long as you keep changing where you stroke. Also, I have machinist's handbooks available, so just shoot me a pm or post up here any questions you feel the book may have answers for.

Very good thread,
Connor
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Hello Connor - I use inline/lateral/sideway motion a lot, especially when I need a finer finish on the same stone. Similar to your approach (where to stroke), I rotate/turn the stone instead, which reduce dish in stone. I definitely will take up your offers of lending eyes to the machinist's handbooks. Please post - sharing your skills & curiousities would certainly help me & others to realize/know what we didn't know or even awared.
 
HeavyHanded said:
I'm curious if you noticed any trends in the post testing blade strategies - did the greater wedging action of the Scandi 'protect' the cutting edge at all, or conversely did the decreased resistance overall allow the full convex to maintain apex geometry longer? There may be other benefits/penalties that are not immediately evident?
Click to expand...
HH - excellent questions (+ good deductions):thumbup:

For 'scandi' & 'blended scandi' their excessive wedging, induced me to exert extra force, along with un-even wedge resistance (more on the left side of the blade). In consequence, the blade steer left (toward cardboard hand) as I thrush down & in (twist some). The edge rolled, which tear cardboard after 5 minutes, I called it quit because it was too un-enjoyable to continue.

I did batoned scandi edge against 2" fresh pine branches for 10 minute, along & cross grain. Along/with grain, it mostly split the branch via wedging. Cross grain - I had to hit it pretty hard (the knife creak a little now). Over all, scandi wedge seem to protect the edge to certain extend, at the end the edge still plenty sharp with no sign of roll or deformations.
scandilbaton.jpg



For 'full convex', yeah it's much more fun to cut cardboard into thin strips. The wedge line is higher up on the blade, so the edge actually cut more (less tear). Also no steering problem. I did touch-up the edge every 10 minutes with DMT EE to keep cutting fun for 30 minutes. Once I tried the Opinel #9 carbon. I was done with the Mora.

btw, a sharpened convex box cutter easily out cut all my folder & fixed blades.

Bottom line: Performance go up as wedging go down for most scenarios, except for spliting long grain stiff material (e.g. wood, bamboo,etc..).

PS, your stripe pattern is similar to the one I used to apply when sharpening full convex on a hard stone - Sharpie only. I've gotten enough of a feel that I do it by looking at the grind pattern, but was a big help when I first gave it a try.
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I've done a lousy job full convex the Mora using 1x30 50grit slack belt. Lost at least 0.5mm blade height and 1mm tip in the process. Later on, I'll reprofile it using diamond plates 140->220->400->etc..
 
Rambling alert:p

Along the way, I encountered a few hot blades from freehand thinning & rapid sharpening strokes against dry abrasives - diamond plate, w/d sand paper, ceramic belt. Didn't think much about them then, just unhappy with many edges from those blades were easily roll. Most roll problem went away after I re-grinded the bevel.

Recent cognizant of this correlation. I re-produced this heat & roll for a few knives in various steels (k390, s35vn, cpm-m4, cpm-154, 52100). Note that cpm-m4 edge doesn't loose rc under 1000F. I found that dull abrasive is the key mechanism for convert & transfer kinetic to thermal (friction + burnish) absorption by the edge. And edge-trailing motion the heat accumulate and flow toward the edge. Abrasive is a thermal insulator, so sharpening interaction start at bevel shoulder start to heat abrasive up. Some of this heat transfer to blade however additional heat get created from interaction (friction, abrasion). Well if the heat delta (new - transfer) is positive, abrasive accumulate more heat (getting hotter). Eventually the thermal transfer for this accumulated heat near & at the apex is very large. Now, with rapid strokes or high pressure and when this accumulating transfer is faster than thermal dissipation, and temperature higher than the blade tempered temperature, a small/thin section (depends on the extend of heat) of apex has been de-tempered.

Oh wait a minute - you :confused:. Easy to think that the blade usually just warm or not beyond too hot to hold/touch, so no way to de-tempered - even for a low temperature tempering steels. Well, the whole blade is a GIANT heat-sink for that relatively TINY mass of the bevel. this stuff is too complicated for using finite element with heat equation, so using my solve-all hand-waving that 'hey my edges roll, therefore the edge did exceed de-temper temp.

Powered sharpeners with dull dry abrasive certainly will amplify this problem. Sure, powered sharp fine abrasives can be problematic too but lesser extent. Steels with high hard carbides by volume also a big factor.
 
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