removing a back bevel

[David C]

My wire edges don't get exercised! (There is a phrase to conjure with). They get honed away, in one operation on a fine waterstone.

Charles, you have clearly never read or seen any of my material, so you are not even in posession of the facts. This confirms my impression that you operate on pure prejudice.

Since you ask so nicely, the ruler I use, is narrow, stainless, six inch and 0.5mm thick.

David Charlesworth

 

[bugbear]

By definition, if a burr is present then one has removed metal past the area of bluntness on both front and back (the 'wear' bevel).

That's quite untrue, "by definition" or otherwise. It's common for a burr well before the abrasion plane has reached the edge. In knife sharpening circles this is so commonly noted that they've given it a name - it's sometimes called a "false burr". Burrs are simply caused when the abraded metal doesn't detach from the workpiece, due to the malleability and ductility of the metal.

BugBear

 

[Trafalgar]

My wire edges don't get exercised! (There is a phrase to conjure with). They get honed away, in one operation on a fine waterstone.

Charles, you have clearly never read or seen any of my material, so you are not even in posession of the facts. This confirms my impression that you operate on pure prejudice.

Since you ask so nicely, the ruler I use, is narrow, stainless, six inch and 0.5mm thick.

David Charlesworth

You may think you're honing it away, and you may be, partially. If you've ever moved the burr from back to front or vice versa then you've exercised the burr.

The only person I know that did it all from one side (honed it away rather than exercised it away) was Tage Frid when he honed chisels, bevel side only, on a running belt sander with a worn out belt and then polished the bevel with compound on a power buffer, again, all from the beveled side, until there was no trace of a burr. It can be done, but you aren't doing it.

We know that you work from both sides. I'm quite sure that you exercise the burr regardless of what you like to call it.

 

[Trafalgar]

By definition, if a burr is present then one has removed metal past the area of bluntness on both front and back (the 'wear' bevel).

That's quite untrue, "by definition" or otherwise. It's common for a burr well before the abrasion plane has reached the edge. In knife sharpening circles this is so commonly noted that they've given it a name - it's sometimes called a "false burr". Burrs are simply caused when the abraded metal doesn't detach from the workpiece, due to the malleability and ductility of the metal.

BugBear

Quite true for a knife that's beveled on both sides to form the cutting edge. For knives, it also depends upon the degree of the hollow grind, the size of the wheel used to produce the grind, and whether the grinding was absolutely perfect and perfectly consistent from both edges. A knife's edge wears completely differently than a plane iron, especially one used in butchering meat where the knife is twisted and turned and even which hand the butcher uses it in. The first thing a quality knife sharpener will ask a butcher is what hand he is - right or left. A lot of this stuff is lost on guys sharpening knives these days for real, working professionals who don't do their own. A right handed butcher will hold a knife about 65+% of the time tilted away from his body and this affects how the edge wears.

In essence, it doesn't apply here.

 

[Jacob]

I really think it'd be a good idea if Dave (and bugbear, Brent Beach and a few others) went off and did a course with Paul Sellers or similar, with an emphasis on sharpening. It (might) give them the basic practical skills which they obviously need and stop them waffling on.
They'd still be free to indulge in "modern" hobby sharpening complexities, but with one foot in the real world!

 

[Jacob]

....

Since you ask so nicely, the ruler I use, is narrow, stainless, six inch and 0.5mm thick.

David Charlesworth

Try it without the ruler Dave - do it the normal way like everybody else. It's easier.

 

[bugbear]

I really think it'd be a good idea if Dave (and bugbear, Brent Beach and a few others) went off and did a course with Paul Sellers or similar, with an emphasis on sharpening.

If you'll pay, I'll go. Teach him a thing or two.


Mind you, he's a back flattening, mirror polishing, Veritas loving traitor these days...

BugBear

 

[iNewbie]

I really think it'd be a good idea if Dave (and bugbear, Brent Beach and a few others) went off and did a course with Paul Sellers or similar, with an emphasis on sharpening. It (might) give them the basic practical skills which they obviously need and stop them waffling on.
They'd still be free to indulge in "modern" hobby sharpening complexities, but with one foot in the real world!

Your recommending people go see a sharpening Guru pratle-on when its a 1min job - and when we all know what you think about sharpening Guru's. I am THE walrus.... coo coo-ca-choo. :mrgreen:

 

[Paul Chapman]

stop them waffling on.

Wish we could find something that would stop you waffling on. You've been at it for years and it's just as boring now as it was when you started.

Cheers :wink:

Paul

 

[bugbear]

By definition, if a burr is present then one has removed metal past the area of bluntness on both front and back (the 'wear' bevel).

That's quite untrue, "by definition" or otherwise. It's common for a burr well before the abrasion plane has reached the edge. In knife sharpening circles this is so commonly noted that they've given it a name - it's sometimes called a "false burr". Burrs are simply caused when the abraded metal doesn't detach from the workpiece, due to the malleability and ductility of the metal.

BugBear

Quite true for a knife that's beveled on both sides to form the cutting edge. For knives, it also depends upon the degree of the hollow grind, the size of the wheel used to produce the grind, and whether the grinding was absolutely perfect and perfectly consistent from both edges. A knife's edge wears completely differently than a plane iron, especially one used in butchering meat where the knife is twisted and turned and even which hand the butcher uses it in. The first thing a quality knife sharpener will ask a butcher is what hand he is - right or left. A lot of this stuff is lost on guys sharpening knives these days for real, working professionals who don't do their own. A right handed butcher will hold a knife about 65+% of the time tilted away from his body and this affects how the edge wears.

In essence, it doesn't apply here.

You apear to think I'm describing a "wire edge" (much derided in knife circles, as opposed to a "true edge").

I'm not, although the fundementals are related.

What I'm describing is simply particles failing to detach (and thus forming a burr) before you've worn the bevel down to fully intersect the back. If you think about, it's actually easier for them to cling on when the angle is less acute, which is the case earlier in the process. So the formation of a burr does not always imply that the
bevel has met the back.

bugBear

 

[Phil Pascoe]

Well, I'd like to say how much better informed I am after reading this thread...but I'd be lying... :roll:

 

[Trafalgar]

You apear to think I'm describing a "wire edge" (much derided in knife circles, as opposed to a "true edge").

I'm not, although the fundementals are related.

What I'm describing is simply particles failing to detach (and thus forming a burr) before you've worn the bevel down to fully intersect the back. If you think about, it's actually easier for them to cling on when the angle is less acute, which is the case earlier in the process. So the formation of a burr does not always imply that the
bevel has met the back.

bugBear[/quote]

I have absolutely no idea what you're talking about - particles detaching before a burr is formed. I assume these can't be felt. I feel for the burr and every time that I have identified that a burr has been formed all the way across a cutter's edge then bluntness has been removed, the edge is sharp, and all that remains is the complete removal of the burr and the polishing off of any stray rag. On a cutter in good shape, when a fine burr has been formed, the latter two steps can easily be accomplished on a strop. Again, the stone has done it's job.

It's so simple. So very simple.

Feel for the burr with the back of your index finger - the portion between the 2nd and 3rd knuckles. If you can feel it, it isn't false. If you have any doubts, offer the cutter to your thumbnail. It will catch, nicely, even with a fine burr still there. It's sharp already. The honing stones have made it so. All you need to do is remove the burr. If you're just jack planing wood don't even bother removing the burr. It'll be gone the first pass and you'll be back to work. If you're doing fine paring with a chisel or very fine smoothing, then remove the burr and smooth the edge with your strop.

 

[Corneel]

That's about as good as it gets.

Another way is using a fine polishing stone instead of a strop, like an 8000 Japanese waterstone. Same principle, different media.

After raising a burr with a 1000 stone, I polish the bevel on the 8000, and then most of the burr is allready gone without attention to the back yet. You can't feel it anymore. There is still some fluff visible under a microscope (when you are idiot enough to look at edges with a microscope). A bit of back and forth between the back and the bevel removes that quickly.

There is no need for backbevels on a bevel down plane iron.

 

[bugbear]

You apear to think I'm describing a "wire edge" (much derided in knife circles, as opposed to a "true edge").

I'm not, although the fundementals are related.

What I'm describing is simply particles failing to detach (and thus forming a burr) before you've worn the bevel down to fully intersect the back. If you think about, it's actually easier for them to cling on when the angle is less acute, which is the case earlier in the process. So the formation of a burr does not always imply that the
bevel has met the back.

bugBear

I have absolutely no idea what you're talking about - particles detaching before a burr is formed. I assume these can't be felt. I feel for the burr and every time that I have identified that a burr has been formed all the way across a cutter's edge then bluntness has been removed, the edge is sharp, and all that remains is the complete removal of the burr and the polishing off of any stray rag. On a cutter in good shape, when a fine burr has been formed, the latter two steps can easily be accomplished on a strop. Again, the stone has done it's job.

It's so simple. So very simple.

Feel for the burr with the back of your index finger - the portion between the 2nd and 3rd knuckles. If you can feel it, it isn't false. If you have any doubts, offer the cutter to your thumbnail. It will catch, nicely, even with a fine burr still there. It's sharp already. The honing stones have made it so. All you need to do is remove the burr. If you're just jack planing wood don't even bother removing the burr. It'll be gone the first pass and you'll be back to work. If you're doing fine paring with a chisel or very fine smoothing, then remove the burr and smooth the edge with your strop.

I think we're describing the same thing, but in differing levels of detail.

To avoid excess ambiguity, I've drawn what I mean.

The drawing is purely of the cutting edge, starting off round (and blunt) and ending up sharp. The progress of the sharpening
is indicated by the successive lines from 1 to 5.

Oh - the particle thing? What I'm talking about is metal that has been cut (a "chip") by the abrasive. If it is removed, it ends up as
swarf. But if it isn't removed, merely moved, you get a burr. The burr
(obviously?) extends beyond the original shape of the tool, so metal must have been moved. It's the same
as what happens when you file a piece of steel, just on a smaller scale.

It is obvious that the abrasive is initially parallel with the metal (line 1 is a tangent
to the round tip). It is obvious that the abrasive is at the bevel angle by the time we reach line 5 (lets call it 30°). It is obvious
that at the mid point (line 3) the abrasive is at 90 degrees to the tip.

So - to burrs. I do not know the lowest angle at which a burr can form. I don't think it can happen
at 0 degrees (line 1). Anyone who's (again) filed a block of metal knows that a burr can form at 90.
What the lowest angle is probably varies with both grit size and metallurgy.

But it would be a profound optmist who believed that burr formation just happens
to be possible for the first time at the chosen bevel angle, regardless of metal
and grit. A burr does not mean you're finished (i.e. line 5 in the diagram).

These early/false burrs are quite easy to feel - but it depends on their size,
It is easy to prove to yourself that burr size definitely depends on grit and metal;
tuning a cap iron (softer steel) will show you huge burrs, far bigger than tool
steel ever shows, and visible to the naked eye.

In practise, this false burr phenomonon causes little trouble. It is avoided by simply
continuing to abrade. Leaning just what constitutes a "proper" burr,
indicating that the blade is sharp just involves trying it. A "big enough"
burr is what you're after, but defining "big enough" by any means
other than physical one-on-one demonstration is hard.

BugBear

(long ago, when sharpening/reshaping a rather soft axe with a coarse carborundum stick, I had a false burr
so big I could actually see it, albeit under magnification)

 

[Jacob]

Sharpening is so difficult nowadays (for some)! It never used to be - any fool could do it.
Somewhat paradoxical that those who find it difficult claim to know how to do it. I think they may be slightly deluded.

 

[iNewbie]

Delusion being your specialist subject...

 

[Corneel]

When you quit sharpening too soon, say at line 3, you still get a sharp edge, but with a steep, microsopic "backbevel". The remaining roundness is on the faceside of the blade.

Is is important to remember that the worn edge of a plane iron doesn't look like your picture. It looks more like this:

Picture from http://bladetest.infillplane.com/html/wear_profiles.html

That means that you first remove the wearbevel on the clearance side of the blade before you can actually feel the burr. Removing this wear bevel is a big part of sharpening a plane iron. The round nose of the dull edge is very small, a radius of just a couple microns. If you dont remove all that roundness, it is not the end of the world, it is just not perfect.

 

[bugbear]

When you quit sharpening too soon, say at line 3, you still get a sharp edge, but with a steep, microsopic "backbevel". The remaining roundness is on the faceside of the blade.

Is is important to remember that the worn edge of a plane iron doesn't look like your picture.

All agreed - despite what people say, I was simplifying!

BugBear

 

[Paul Chapman]

Sharpening is so difficult nowadays.

Don't worry, Jacob, you'll get the hang of it eventually..........

Cheers :wink:

Paul

 

[Jacob]

.....
swarf. But if it isn't removed, merely moved, you get a burr. The burr
(obviously?) extends beyond the original shape of the tool, so metal must have been moved.......

I thought I'd join in the waffly burr burbling.
The burr isn't metal which has been moved - it's just been left behind. As the honed edge approaches 5 in BB's drawing, the metal left between 4 and 5 is thin enough to be pushed out of the way rather than honed off. This is really noticeable with some laminated blades where the harder steel of the face can remain as quite a wide but very thin foil, bending upwards as the softer bevel behind it is removed. A bit like grating an apple - the soft insides get grated but bits of peel lift away and remains as a flap still attached (sometimes).