Need a burr?

[HeavyHanded]

I honestly do not believe this to be the case most of the time. The biggest issue most freehanders need to overcome is excessive angle wooble.

Too much wooble leads to an angle that is more broad than intended, and the less acute the edge, the quicker it dulls. This is why most folk can make a coarse or medium edge and have increasing trouble as the level of polish increases. My theory anyway...

 

[Steel_Drake]

Any of you guys have any videos of " no burr" Sharpening?

I've got a few on my YouTube channel as I usually use a burr minimization sharpening approach when I sharpen my knives.

This is a good one for showing how quickly a three step approach with a low edge bevel angle can restore high push cutting sharpness on a knife using only a 1k waterstone and a coarse particulate abrasive strop. On my channel I have other videos where I use a three step sharpening method, including a full length tutorial if you are interested.

but the notes also described the edge finish as being increasingly coarse as the angle decreased

As I understand it, this occurs because the valleys between the teeth created in the scratch pattern at a particular grit get deeper as the edge bevel angle gets lower, meaning the same grit of abrasive actually produces a coarser apex finish at lower angles.

All things being equal, thinner is better up to about 8° per side and then thinner doesn't seem to yield any improvement (assuming a common microbevel. Lateral stability drops way off as angle decreases though, so as always it is important to tailor the edge to the job if possible.

That's pretty much the same conclusion that Cliff came to, that 7-9 degrees per side with a microbevel was usually as thin as it was practical to go.

Again, there doesn't seem to be any correlation between retention and burr/burless strategies that I could find

So long as any burr formed is successfully removed prior to completing the sharpening process there should be no edge retention difference between a burr based and burrless approach. A burrless approach is just faster and wastes less steel. It's the use of a lower edge bevel angle and microbevel in a three step approach that can have performance benefits due to reduced force required to make cuts and the lower skill required to obtain a crisp burr free apex line when setting a microbevel with a limited number of passes.

 

[HeavyHanded]

That's pretty much the same conclusion that Cliff came to, that 7-9 degrees per side with a microbevel was usually as thin as it was practical to go.


So long as any burr formed is successfully removed prior to completing the sharpening process there should be no edge retention difference between a burr based and burrless approach. A burrless approach is just faster and wastes less steel. It's the use of a lower edge bevel angle and microbevel in a three step approach that can have performance benefits due to reduced force required to make cuts and the lower skill required to obtain a crisp burr free apex line when setting a microbevel with a limited number of passes.

Again, so much of this is in the details. Most of the deleterious effects of burr formation result from too much pressure and poor quality of the abrasive surface. Short of having a perfect line to work on, all edge reset will result in uneven grinding from shoulder to apex and so some burr formation. Realistically, only the deformation of steel away from pressure is what needs most to be avoided, as this is what causes the most subsurface weakening.

The burrs that form from scratch trough grinding with pressure below needed to deform the steel, don't extend into the angle formed by the two planes joining, so they will effect edge retention less than the other effects (edge finish, carbide content, etc). Cleanly remove this waste and the issue is a non-issue.

My own work showed a linear (near) correlation between edge finish and retention based on cutting mechanics with a static edge angle. The issues with microbevel or single bevel application peak when small deviations in angle effect the outcome at very low angles. A microbevel is not less susceptible to these effects, and the presence of a burr at the rough grind phase is equally inconsequential.

 

[Steel_Drake]

Again, so much of this is in the details. Most of the deleterious effects of burr formation result from too much pressure and poor quality of the abrasive surface. Short of having a perfect line to work on, all edge reset will result in uneven grinding from shoulder to apex and so some burr formation. Realistically, only the deformation of steel away from pressure is what needs most to be avoided, as this is what causes the most subsurface weakening.

In case i wasn't clear initially, I don't there there are any deleterious effects of burr formation so long as that burr is cleanly removed prior to finishing the sharpening process. A burr is only an issue if it isn't removed. In comparing a burr based approach where the burr is removed and a burr minimization sharpening approach at the same edge bevel angle with the same microbevel finishing step, I don't believe there would be any reason for one or the other to have a performance advantage. As I said, in this regard I think the only advantage of a burr minimization approach is that its faster and wastes less steel.

The burrs that form from scratch trough grinding with pressure below needed to deform the steel, don't extend into the angle formed by the two planes joining, so they will effect edge retention less than the other effects (edge finish, carbide content, etc). Cleanly remove this waste and the issue is a non-issue.

I think I may have misunderstood what you were saying in your previous post: The point I made about lower angles producing coarser apexes on a given abrasive grit was totally separate and unrelated to anything about burrs. I was just noting that the actual finished apex will be coarser at a given grit of abrasive as the apex angle is lowered because the scallops in the scratch patterns on the two sides of the apex will meet further behind teeth on the apex line creating deeper scallops between the microscopic teeth as the apex angle is lowered. This just means that a DMT C will give an effectively coarser finish on a knife sharpened at 10 degrees per side than 20, even though the grit of the abrasive is the same.

 

[HeavyHanded]

In case i wasn't clear initially, I don't there there are any deleterious effects of burr formation so long as that burr is cleanly removed prior to finishing the sharpening process. A burr is only an issue if it isn't removed. In comparing a burr based approach where the burr is removed and a burr minimization sharpening approach at the same edge bevel angle with the same microbevel finishing step, I don't believe there would be any reason for one or the other to have a performance advantage. As I said, in this regard I think the only advantage of a burr minimization approach is that its faster and wastes less steel.

You may be 100% on this. I'll point out one thought, since the common use of the plateau method begins with grinding off the entire existing apex, there is likely no difference in the amount of removed total steel one way or the other. If you do as Brent Beach recommends and stop your rough grind short of the apex and without first destressing, then you are liable to see a small reduction in lost steel.

I think I may have misunderstood what you were saying in your previous post: The point I made about lower angles producing coarser apexes on a given abrasive grit was totally separate and unrelated to anything about burrs. I was just noting that the actual finished apex will be coarser at a given grit of abrasive as the apex angle is lowered because the scallops in the scratch patterns on the two sides of the apex will meet further behind teeth on the apex line creating deeper scallops between the microscopic teeth as the apex angle is lowered. This just means that a DMT C will give an effectively coarser finish on a knife sharpened at 10 degrees per side than 20, even though the grit of the abrasive is the same.

I am not convinced of this relationship. Normally, you get a deeper scallop as the approach angle becomes less acute, not more. This is easily demonstrated with a file on a piece of flat stock, working at varying angles to meet at the centerline.

In any event this effect should not be all that pronounced one way or the other so long as light pressure is being used. Variation in the mean protruding height of the abrasives will likely be far more than the difference in abrasive depth as the angle changes.

 

[Steel_Drake]

You may be 100% on this. I'll point out one thought, since the common use of the plateau method begins with grinding off the entire existing apex, there is likely no difference in the amount of removed total steel one way or the other. If you do as Brent Beach recommends and stop your rough grind short of the apex and without first destressing, then you are liable to see a small reduction in lost steel.

My own experience in using a burr minimization approach that starts with grinding off the existing apex versus a burr based approach is that the burr minimization approach is consistently faster than the burr based approach on the same knife at the same starting abrasive grit, I would infer from this that the amount of metal removed by removing the existing apex into the stone before starting is likely less than the amount of steel driven into the burr region when using a burr based approach. This is merely an inference, however.

I do think there are performance advantages in using lower edge bevel angles and microbevels rather than using a single edge bevel angle all the way to the apex, but I don't think those advantages are particular to the burr minimization sharpening approach per se and the same benefits from those things would occur if applied to a burr based approach so long as the burr was properly removed prior to apexing. If anything, it's just that the three step approach encourages its users to lower their edge bevel angles and use microbevels to apex.

I am not convinced of this relationship. Normally, you get a deeper scallop as the approach angle becomes less acute, not more. This is easily demonstrated with a file on a piece of flat stock, working at varying angles to meet at the centerline.

I'm going to see if I can think up a practical way to test this because I can't present any compelling empirical evidence to support the idea that the same grit at lower apex angles produces a deeper scallops between the teeth on the apex, I'd simply accepted it on the basis of the data presented.

In any event this effect should not be all that pronounced one way or the other so long as light pressure is being used. Variation in the mean protruding height of the abrasives will likely be far more than the difference in abrasive depth as the angle changes.

I wasn't meaning to try and assert how pronounced the effect was relative to other factors, I think there are several other performance advantages from a lower apex angle that would outweigh any potential coarsening of the apex on a given abrasive grit.

 

[SV-97]

Imo sharpening without a burr(If you can pull it off) is better because there's no risk of a wire Edge(OK I usually have another reason but can't recall it right now)

 

[HeavyHanded]

My own experience in using a burr minimization approach that starts with grinding off the existing apex versus a burr based approach is that the burr minimization approach is consistently faster than the burr based approach on the same knife at the same starting abrasive grit, I would infer from this that the amount of metal removed by removing the existing apex into the stone before starting is likely less than the amount of steel driven into the burr region when using a burr based approach. This is merely an inference, however.

Again this is possible and likely if folks lean on it but I am not convinced it is a foregone conclusion by any means. You could make the same inference if someone leans too much on the destressing stage, particularly with acute edge angles. Most of the burr material comes from the last bit of bevel surface being pushed off the end, rather than being undercut from the bevel itself.

I do think there are performance advantages in using lower edge bevel angles and microbevels rather than using a single edge bevel angle all the way to the apex, but I don't think those advantages are particular to the burr minimization sharpening approach per se and the same benefits from those things would occur if applied to a burr based approach so long as the burr was properly removed prior to apexing. If anything, it's just that the three step approach encourages its users to lower their edge bevel angles and use microbevels to apex.

I too believe there are performance advantages, I have no doubts at least on some steels and angles the difference is notable. On others not so much. I believe this also extends in a similar manner to very shallow convex grinds.

To my way of thinking and working, the microbevel is pretty much necessary to the burless approach. The level of skill and angle holding needed to do a single bevel with no burr is pretty exacting and I'd agree time consuming - you can do it a lot faster just accepting and removing any burr that forms. I'll add that I find most of the advantages to microbevel only hold true when using a finer abrasive for the micro - otherwise I don't see much of an improvement in edge quality or time.
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Add the micro and as long as the edge started out with no burr it IS relatively fast and easy to finish it off, this is how I normally sharpen commercially. In that case I go to three finger sticky +visual inspection to set the edge and if there's a burr or not does not concern me much - remove it and microbevel. I don't shoot for a burr on purpose, but the edge does need to be fresh ground to the edge. If I stop right on or go over a bit is all good. Better that than stop too shy and have to expand the microbevel.

 

[DainBramage1]

I've got a few on my YouTube channel as I usually use a burr minimization sharpening approach when I sharpen my knives.

This is a good one for showing how quickly a three step approach with a low edge bevel angle can restore high push cutting sharpness on a knife using only a 1k waterstone and a coarse particulate abrasive strop. On my channel I have other videos where I use a three step sharpening method, including a full length tutorial if you are interested.

I was going to ask where the link was, as I can't see it within the forum, but when I quoted your comment, I could see the YouTube reference. I'm really curious about burrless sharpening... thanks!