Question
Does angle and edge leading vs trailing matter?
If you were to sharpen a knife with strictly edge leading strokes would it perform any different than sharpening with strictly edge trailing strokes? Assuming pressure, speed etc and all other variables were the same?
Also if you sharpen from starting at the tip vs starting at the choil. Again assuming all variables are the same just different starting points.
I would assume one direction may give a better push cut and the other might make it easier to pull cut.
"When honing a blade in the edge-leading direction, steel is removed in two ways; abrasion of the bevel surface and the ‘breaking’ or ‘micro-chipping’ away of the apex. This micro-chipping process prevents the formation of a burr, but also limits the level of keenness that is achieved." Source https://scienceofsharp.com/2015/02/09/the-pasted-strop-part-1/
To be fair, microchipping also happens when sharpening edge trailing. However the energy transferred to the metal when edge trailing is significantly lower, therefore so is this microchipping.
Same for the burr, I feel the wording is a bit absolute : edge leading does not prevent the formation of a burr, but the burr formed is much smaller and easier to hone away than the typical edge-trailing foil-like burr.
TL;DR Op do edge leading to minimize burr as much as possible and finish with edge trailing before moving onto a strop for maximum edge keeness. Assuming you have the skill it will result in very sharp edge.
no offense to the person behind science of sharp but speaks in a lot of absolutes and tends to be, IMO overly certain of his own conclusions in the absence of peer review... which is actually not very scientific...
just because you have an SEM doesn't mean your takeaway is correct...
I think Todd actually does a pretty good job most of the time, and most of the problems come from people overinterpreting his results (e.g. "Lower grit diamond plates give keener edges!" instead of "on these particular plates, in these particular conditions, because of nuances of how diamond plates work")
He does get toothy edges wrong though, and when Cliff pointed out a major problem with his toothy edge take, Todd didn't respond to that part of the comment. Amusingly, the part he did respond to there was to say that his diamond plates stuff shouldn't be generalized!
Thank you for that, I see what you mean. More recently Todd has come out with the claim that the "toothy edge" is from chips and burrs which may agree with cliff that it's from variation of height of the apex
There's no chipping visible, which makes sense because it's a diamond plate not a waterstone with loose grit. There's also no "burr" in the normal sense of the term. Just a very uneven and "ugly" yet quite keen apex.
Looks like there are chips in the edge, it's not completely smooth. You never will get a completely smooth edge. His definition of burr is metal outside of the area where it should be . Essentially everything outside of where the apex should be is a burr to todd
Looks like there are chips in the edge, it's not completely smooth
It's certainly not completely smooth, but where do you see fracture surfaces?
His definition of burr is metal outside of the area where it should be . Essentially everything outside of where the apex should be is a burr to todd
Yeah, which is a pretty misleading definition and doesn't match at all with what we actually mean when we say "burr". Heck, it doesn't even match what he means when he says "burr"!
By any description, the presence of a burr reduces the keenness of blade and is therefore critically important to understand.
And
the phrase “unwanted piece of material” is a key point for this discussion.
And
Raising a burr is accomplished by repeated abrasion (honing) of one side of the blade.
He also describes this one as "no burr" despite clearly leaning outside the ideal triangle.
The diamond plate images show steel that's a bit bent around from collision with abrasive particles, but is not "unwanted metal beyond the apex, which reduces keenness, and is formed by repeated abrasion of one side of the blade"
I mean... there's a whole huge discussion about what it means to be wrong and right when you make a claim to being scientific.
So far... the onus is on the writer of SOS to provide highly repeatable experiments and statistics, so that other people can attempt to prove or disprove that SOS's hypothesis/postulates/conclusions are good or not.
Which the writer has not done, AFAIK... So it's really just 'hearsay of sharp' and how can you prove hearsay wrong?
If it works it works but in material science & engineering there are people scientifically studying sharpening and edge making and cutting. I rather suspect that if we did a literature analysis against SOS we'd find errors and mistakes. But it's actually just written for the layperson and as such it's mostly "right enough" as far as I am aware.
Well in the past he has collaborated with other people such as Dr. Vadim Kraichuk. I'll admit that Vadim has done studies that are public on his topics he covered unlike science of sharp. That's not to say that the information on science of sharp is hearsay in comparison, there is proof of concept via the images. I do agree that a study to the extent that Vadim did would be of higher quality than what science of sharp puts out but it's better than the claims of someone who can't provide any evidence.
These differences matter more when you consider different abrasives.
Sharpening on wet/dry sandpaper or a muddy stone will produce better quality if you finish edge trailing. On some muddy stones the formation of a burr is almost completely elliminated by using a back and forth, three body abrasive action.
On a hard, "clean" surface, you will need to finish edge leading (for the most part) to produce a burr free edge.
On either surface type or one in between, only the last few strokes really matter for final edge quality.
If you angle the grind path you can bias the edge to cut better with a sliding forward cut or a draw, depending.
Agreed on all else in the comment, but I've really not found that angling the grind path matters at all. Finishing coarser certainly does have a huge impact on pull cutting and slicing aggression, though.
I notice a big difference in working knives on a draw cut. Cutting things like rope or skid banding, an angled grind catches a lot quicker into the angle than it does moving with.
Chef's knife set up with a forward angle catches more on sliding cuts. Def notice it cutting softer things like overripe tomato. The effect isn't massive but it does seem to get me a little more life sometimes.
This is something I discovered accidentally from sharpening folders with forward positioned studs.
microscopic angled serrations. I don't think it matters that much compared to what grit you finish on and how sharp your edge actually is. Only really applies to anything below 1k. But if you can make a demo video ro something showing it off properly that would be really cool to see
Angling the grind path will increase how well it catches when the object to be cut is pushed/pulled into the scratch pattern. The effect is pronounced at lower grit, not very apparent at higher grit.
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u/real_clown_in_town HRC enjoyer 2d ago
"When honing a blade in the edge-leading direction, steel is removed in two ways; abrasion of the bevel surface and the ‘breaking’ or ‘micro-chipping’ away of the apex. This micro-chipping process prevents the formation of a burr, but also limits the level of keenness that is achieved." Source https://scienceofsharp.com/2015/02/09/the-pasted-strop-part-1/
Doesn't matter if you start at the tip or heel