How much wrong with edge-following movements?

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kreisler

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We know edge-leading movements (elm): on whetstones for grinding, sharpening, apexing, burr creating, shearing off burr.
And we know edge-trailing movements (etm): more common on non-stones (like felt, paper, leather, wood, cardboard, etc), for deburring, stropping.

What about edge-following movements (efm)?
  • Ex.1: Users of guided rod sharpening systems (GRSS) naturally get to efm sooner or later, e.g. once they've reached the polishing stage (3000, 5000, or 10000 grit natural stone) and realize that elm or back'n forth movements aren't effective any longer because steel material removal is too slight. At this point it feels right/natural to move the rod sidewards, sweeping from side to side, following the direction of the edge line.
  • Ex.2: When sharpening sickles or scythes with a ceramic rod (like 204M), i also naturally end up using wiper-like movements of the ceramic rod, i.e. the sickle's edge gets sharpened in direction of the curved edge line. In contrast, elm or etm would be rod movements in direction of the rod axis, perpendicular to the edge line, but such movements would consume the friable 204M right away because of the sickle's edge aggressiveness.
  • Ex.3: When polishing a chef knife on a narrow benchstone or doing balancing strokes on a narrow benchstone, the bevel at the heel area gets a scratch pattern which aligns more with the edge line, whereas the bevel at the tip area gets a scratch pattern which aligns more with perpendicularity. This is a result of how one swipes the entire blade in one single movement across the benchstone surface (see burrfection).
  • Ex.4: Balancing strokes obviously reduce the zig-zagginess (toothy-ness) of the local apex line. Efm takes it up a notch, making the entire edge line smooth, also reducing the belliness of a belly.
We don't talk much about efm, is there anything wrong with it?
Question is, is efm a common sharpening technique (anyone who uses it deliberately other than me?) or does the side-to-side wiper technique have a detrimental effect on the steel matrix?

I once thought that efm with a 204UF, which produces a mirror-polished bevel yay!, should also naturally reduce and eventually remove the microburr but fact is, efm with an ultrafine stone produces a mirror finish but also, surprisingly, a burr (on the opposite side). No problem though, one can deburr then with standard techniques.
 
When I was taught to sharpen by father, uncles, ants, grand parents (grandmothers sharpened their own) grandfathers, maternal great grandfather and grandmother, and maternal great-great grandmother) 60 odd years ago, they were unanimous on this:
Burrs are bad. If you get a burr/wire edge, you 🤬 up.
Leading with the edge prevents a burr/wire edge.
Edge trailing causes a burr/wire edge.

They were also adamant about sharpening to an acute edge. 10 to 15 degrees per side for a knife. 15 to 20 degrees a side on an axe, hatchet, adze, or other chopping tool. ("chopping tools" did not include a knife of any size back then.)
 
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Edge following has been used for many, many years with wood working tools. In addition, plane blade sharpening has several guided clamps with rollers that are specifically designed for edge following. This does minimize the wire edge burr on stones.
Japanese sword makers also use edge following for sharpening and polishing.

Regards,
FK.
 
I seem to recall that the KnivesShipFree videos for sharpening convex edges recommend etm.

Also, I just saw a video where a guy was sharpening Maxamet. He stated that he sharpened all of his steels using one back-and-forth motion so that all the scratch pattern marks would be perpendicular to the edge (he didn't use the words "perpendicular to the edge," but that's how I would describe it). He avoids any "sidewards, sweeping from side to side, following the direction of the edge line" when he's sharpening on a stone. It was his thought that people were having trouble sharpening Maxamet because their scratch marks were all over the place. (He was using a Diamond stone.)
 
Yes, scratch pattern perpendicular to the edge line is the standard we see on factory edges, e.g. Stanley utility blades or scissors. It's probably the most useful (robust, universal functional) pattern.

However, on a sickle, that's impossible to do neatly by freehand with an abrasive rod. Following the edge with an abrasive is much easier\natural by freehand.

Maybe the resulting edge isn't as robust? It certainly cuts. Do we have microscopy pictures of such edges?

Today i sharpened a chef knife with efm and the method took off a lot of steel (not my intention, argh). Was a successful try, and i kinda liked it. Very effortless work. So easy to hold a steady angle, resulted in an absolutely beautiful geometric bevel, better than one could have achieved on a normal GRSS (which comes with rectangular stones).

The main advantage of freehand efm sharpening is: the effortlessness.

Just perfect for the lazy worker me.
 
kreisler said:
Yes, scratch pattern perpendicular to the edge line is the standard we see on factory edges, e.g. Stanley utility blades or scissors. It's probably the most useful (robust, universal functional) pattern.

However, on a sickle, that's impossible to do neatly by freehand with an abrasive rod. Following the edge with an abrasive is much easier\natural by freehand.

Maybe the resulting edge isn't as robust? It certainly cuts. Do we have microscopy pictures of such edges?

Today i sharpened a chef knife with efm and the method took off a lot of steel (not my intention, argh). Was a successful try, and i kinda liked it. Very effortless work. So easy to hold a steady angle, resulted in an absolutely beautiful geometric bevel, better than one could have achieved on a normal GRSS (which comes with rectangular stones).

The main advantage of freehand efm sharpening is: the effortlessness.

Just perfect for the lazy worker me.
Click to expand...
Truly parallel scratch patterns are prone to weakening the apex, making it more susceptible to deformation and damage from side-loads. You would NOT want edge-parallel scratch patterns on sickles, as they are slicing tools and benefit from a crisply-finished coarse scratch pattern with a forward bias (scratches oriented like the teeth of a push saw.)
 
Whew, a really big subject IMO. For the most part, I find that etm for knives is far better for the apex than edge leading. This may also hold true for more obtuse edges but I have yet to play with that. For starters ToddS has found that etm edges can be up to 10 fold keener than elm edges, I read this after concluding etm strokes cause less stress to the apex than elm strokes. My first clue was watching microchipping develop with a microscope. Keep in mind that when you remove material by grinding you also create microfractures in the substrate. The faster the stone removes material the deeper the fractures, so beware of super aggressive stones!

The only cutting tools I know of that are not primarily sharpened perpendicular to the cutting edge are knives. For me the closer to perpendicular the better.

This barely touches the topic but I need to get to work.
 
When a grit particle passes across the apex there are three possible outcomes at that point; a slight burr, a perfect triangle, or a microchip. Very generally, edge leading is more likely to cause microchips and edge trailing more likely to leave a slight burr. Understand that the end result is the statistical average of millions of these interactions. For a given steel/hone/angle you are more likely to form a burr edge trailing and more likely to create a "broken burr" apex in the edge leading direction. BUT you can definitely form a burr edge leading or a broken-apex edge trailing depending on the steel/hones/angle.

I haven't looked at edge parallel/following very often, but in every case that I did at it was indistinguishable from edge trailing - so more likely to form a burr and less likely to form microchips.

One of the reasons that pull-through sharpeners produce sub-standard edges is that they tend to produce small burrs, weakened by scratches near and parallel to the apex.
 
I wonder how much the "prone to microchipping" has to do with the way the abrasive enters the material to be ground? With edge trailing, it enters gradually where the two bevels meet, with edge leading it enters abrubtly into a fairly unsupported apex, which I think is prone to catching. Think of filing the edge of a piece of sheet metal. Edge trailing strokes will be smooth and edge leading will catch and grab. I think the lower the angle sharpened to the more this becomes an issue. I also think the sharper the abrasive the more of an issue this is, think diamond vs aluminum oxide.
 
Maybe counterintuitive, but lower angle sharpening tends to form burrs more readily than higher angle in many steels. At the lower angle the burr is thinner and able to flex without damage, as well as the angle that the burr is flipped is less.

It doesn't seem that a microchip typically forms with just a single grit-particle interaction, rather there is built-up pre-existing damage (like a micro-crack or other sub-surface damage) that increases the chance of micro-chipping.

Loose grit seems to be much more likely to cause chipping, as those particles will sit proud of the surface when the apex crosses - this is why Japanese synthetics are so effective at avoiding burrs, particularly in the edge-leading direction.
 
kreisler said:
And we know edge-trailing movements (etm): more common on non-stones (like felt, paper, leather, wood, cardboard, etc), for deburring, stropping.

What about edge-following movements (efm)?
Click to expand...

Is anyone else unclear on how "etm" and "efm" are different?
 
rhino said:
Is anyone else unclear on how "etm" and "efm" are different?
Click to expand...
etm is the 100% opposite direction of edge leading. on leather , you never do elm (nor efm) . elm would cut into the leather right away, efm would slice into the leather eventually.
on a straight razor, for example, elm is movement perpendicular to the edge line. etm is perpendicular to the edge line too. efm would be perpendicular to etm, i.e. efm would be perpendicular to elm too. efm would be in direction of the straight edge line.
on a straight razor, for efm you would push or pull in direction of the handle (handle axis).
 
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