Clarity Needed Please

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robinbj

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Jul 29, 2015
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So, just read the Buck Guide to Sharpening. They state to grind in and hone a new primary edge by drawing the blade across the stone in a leading motion into the primary edge, not a trailing "stropping" motion. And to finish the edge to do the same.

Ive always been taught, and learned that when re establishing a new primary edge, you can grind in either direction, but to finish and refine that edge, you strop on a fine grit stone in a trailing motion? How do you all feel about this? Whats your opinion?
 
robinbj said:
So, just read the Buck Guide to Sharpening. They state to grind in and hone a new primary edge by drawing the blade across the stone in a leading motion into the primary edge, not a trailing "stropping" motion. And to finish the edge to do the same.

Ive always been taught, and learned that when re establishing a new primary edge, you can grind in either direction, but to finish and refine that edge, you strop on a fine grit stone in a trailing motion? How do you all feel about this? Whats your opinion?
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For establishing the edge, grinding in either/both directions is fine, and a back & forth scrubbing motion is much, much faster at removing metal. For finishing/refining, most people would likely prefer an edge-leading stroke (edge moving INTO the stone) to cut away burrs and leave the strongest-possible steel at the apex. Edge-trailing can sometimes work though; a lot depends on individual skill and use of pressure. Edge-trailing ('stropping' stroke) on stones or hard-backed sandpaper can often generate more/larger burrs if not done carefully, and also depending on the steel being sharpened (low-alloy stainless can be troublesome with burrs). The edge-trailing stroke will move steel towards the edge, and some of that will be weakened steel (burrs/wires, in other words). Edge-leading moves that weakened steel up the bevels and away from the apex, and this is why it's usually easier to leave the edge crisper and stronger with an edge-leading pass.


David
 
Makes sense, I was always of the mindset of trying to move material to the absolute edge, and then to use a soft piece of balsa wood to remove the small edge bur that would form
 
robinbj said:
Makes sense, I was always of the mindset of trying to move material to the absolute edge, and then to use a soft piece of balsa wood to remove the small edge bur that would form
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That's part of why the steel type and hardness makes a difference in what works or doesn't. Some steels (like 420HC, VG-10, ATS-34) will produce amazingly tough burrs that can't or won't be removed in wood or other means used to break or scrub them away, and they'll be more effectively removed by abrading them off on a stone or an aggressive strop. With such steels, edge-leading passes on a stone at a slightly elevated angle and very, very reduced pressure will work best to gently file the ductile burrs off. An 'aggressive strop' is what I'd call something like denim with an aggressive polishing compound like white rouge or other AlOx compounds, or perhaps black compound or polishing pastes like Flitz, Simichrome or Mother's Mag polish used on the denim. These all work very well in removing burrs FAST, and they'll polish very fast as well.


David
 
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Whether you can finish off with a trailing or leading pass is determined mostly by the type of stone you're using.

For the most part burrs are most easily removed with a leading pass.

A super hard fixed abrasive will turn up burrs (generally) if used with a trailing pass to finish - this category would include diamond plates and fired vitreous stones like the India.

When it comes to waterstones, or abrasives applied to papers and films things work a little different. A softer stone will allow a small bit of mobility to the abrasive and will be less likely to turn up a new burr. An even softer stone will not work well at all if used with a leading pass to finish. Where a given stone fits can only be determined by trial and error.

Keeping in mind, some waterstones are very hard and work best with that leading pass to finish. Also, some vitreous stones with loose bonds such as jointer stones, can work very well with a trailing pass, but not generally the ones marketed for hand sharpening. And in some cases the use of oil or slurry can sometimes allow for a trailing pass on stones or plates that otherwise would be unsuitable.
 
Obsessed with Edges said:
That's part of why the steel type and hardness makes a difference in what works or doesn't. Some steels (like 420HC, VG-10, ATS-34) will produce amazingly tough burrs that can't or won't be removed in wood or other means used to break or scrub them away, and they'll be more effectively removed by abrading them off on a stone or an aggressive strop. With such steels, edge-leading passes on a stone at a slightly elevated angle and very, very reduced pressure will work best to gently file the ductile burrs off. An 'aggressive strop' is what I'd call something like denim with an aggressive polishing compound like white rouge or other AlOx compounds, or perhaps black compound or polishing pastes like Flitz, Simichrome or Mother's Mag polish used on the denim. These all work very well in removing burrs FAST, and polishing very fast as well.


David
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Hey man, shot you an email via your BF account.
 
bodog said:
Hey man, shot you an email via your BF account.
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I'm watching for it. For some reason, getting emails via BF's forwarding system seems hit-or-miss at times. Some I've never gotten, and still others sometimes take days or weeks to come through.


David
 
Murray Carter makes kind of a big deal about edge trailing strokes being used for finishing. He does these on the 1000 grit stone to finish. Then on the 6000 grit stone, he does *only* edge trailing strokes. I don't think he talks about why this is important, but he shows it very clearly.

The fact that he mostly works with King stones ties in with what Heavy Handed said about the substrate hardness. Waterstones are mostly sort of soft. King are known to be rather soft. So the fact that Carter gets incredible results from edge trailing strokes on King stones makes sense with Heavy's observations.

I still struggle with waterstones and have almost given up using them.

Brian.
 
bgentry said:
Murray Carter makes kind of a big deal about edge trailing strokes being used for finishing. He does these on the 1000 grit stone to finish. Then on the 6000 grit stone, he does *only* edge trailing strokes. I don't think he talks about why this is important, but he shows it very clearly.
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Does he not follow this by ripping the burr off by cutting into a piece of wood?
 
i use the edge first motion for the courser grades and only switch to a spine first stroke on the finest stone and then on the compound loaded leather strop. I have found this gives me the best edge and it also makes the process faster.

the best way to go about it is to try different methods so you can find what works best on YOUR knife. different steels and geometries behave differently
 
ToddS said:
Does he not follow this by ripping the burr off by cutting into a piece of wood?
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From what I have seen, he always finishes with some sort of backhone, either off the 6k or off newsprint. I'm imagining the burrs he forms at that stage are extremely small - the ones I get using his method are, and he must have better technique than me...Also he tends to use high RC carbon steel quite a bit, not prone to forming large burrs in the first place.

The King 6k is a softish stone with very little feedback, so using a leading pass on it will often make an edge less acute, though it can be done. Another factor that comes into play when I use this method, often I won't completely overgrind the previous scratch pattern. This can leave a very catchy edge that is still very narrow across the apex.

Doing light leading passes to incompletely overgrind a coarser finish using a finer hone doesn't seem to accomplish the same effect - the closest is to polish the entire bevel and then apply a microbevel using a less refined hone.
 
ToddS said:
Does he not follow this by ripping the burr off by cutting into a piece of wood?
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I just watched a little part of his blade sharpening fundamentals video again to refresh my memory. The answer is yes and no. Yes, he lightly draws the blade through some soft wood. *Then* he does more edge trailing strokes. Usually just a few.

Ken Schwartz says that Carter's three finger test (I'm paraphrasing) "favors a 6k edge". I can't remember if Ken commented on the "ripping off the burr", but I think he did, as Ken is big into grinding away the burr instead. I mention this for a good reason: The three finger test tends to fail for me on a LOT of edges I make. Even edges that will pop hairs off my arm don't always feel "three finger sticky". Ken was explaining why certain finishes, like the one that Carter uses, feel sticky. I guess it's the microscopic structure of the edge *at* the edge.

This is a bit off topic, but I thought it was worth discussing.

Brian.
 
Brian, I've tried to catch this with a micrograph but haven't been able to, though I believe it is visible when looking through the eyepieces. The backhone waterstone edge seems to have more variation along the cutting edge up and down, and very narrow apex width.

To get the same up and down variation using a leading pass on harder stones will leave you with a wider apex. You'll have to move to a finer abrasive to thin the apex and the amount of up and down variation will decrease.

Simply applying a fine hone to a coarse edge will leave you with a sizable range of up and down variation on a thinner apex, but the formations will not have the same number/density of "teeth" per unit of length. The next closest effect I have been able to get is by applying a smooth steel to a medium finish edge - the plastic deformation that refines the edge also compresses the apex width and you get a high density of variation on a narrow apex.

Of course...until I capture this effect on camera or some other verifiable means it remains pure speculation :)
 
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