Wear bevels, micro bevels & sharpening - latest thinking?

[ian maybury]

I've been reading Brent Beach's stuff on using multiple micro bevels again, and wondering what the latest thinking might be. He reckons they speed up sharpening and reduce the need for too much use of coarse grits which he suggests may leave scratches, micro cracks and other defects that reach down below the surface of the steel - and which can lead to edge chipping and premature failure in use. He does a great (if slightly heavy reading) job of focusing up the issue of wear bevels and their implications for sharpening - that true sharpness requires honing back past them on both sides of the blade.

Against that i have Veritas bevel up planes (mostly O1 blades) and mostly Japanese chisels (some Koshimistsu/Matsumura white paper steel items) which complicate application of these principles - not to mention that the issues are less with the hollow backs and soft bevel above a hard edge construction of the chisels. I'm using Shaptons in their recommended grits.

So far (and I'm relatively new to high end sharpening) I've been doing fine. (I think - but it's still fairly early days) Taking care to hone the primary bevel back enough to definitely get past the wear bevels, and avoiding coarser grits when flattening the backs for fear of leaving damage/deep scratches behind which would be very hard to polish out, and which may weaken the cutting edge.

There's a bit of setting up to be able to consistently put his three micro-bevels on both sides. (on the plane blades - it's bad practice on the flat side of a chisel) Guess i'm wondering if it delivers enough benefit to try out? Faster sharpening? Longer lasting/more robust edges? (as a result of locally polishing out scratches left by use of coarse stones) Better performance?

Some related questions. I'm very wary of honing bevels on the back of a bevel up plane blades - for fear of reducing the clearance angle too much. Does anybody have experience of doing this? Better still of playing with reduced clearance angles, and able to comment as to what happens at what angles as problems develop? What's a good minimum clearance angle?

It's not recommended, but is using a micro bevel on the primary bevel side of the chisels likely to have noticeable effects?

How big a deal in practice is the risk of scratches left by using coarse stones (presuming they are not fully polished out) to flatten blade backs or primary bevels causing chipping/premature edge failure? How coarse is it wise to go without triggering the need for a major polishing effort to remove scratches/how are you guys handling this issue?

ian

[Kees Heiden]

When you want to see the latest in research about this subject, have a look at Steve Elliott's page. For example this one: http://bladetest.infillplane.com/htm..._profiles.html
Here you see how an edge in a handplane wears in reality.
Another interesting article is from the Japanese professors, which has similar pictures but made with an electron scaning microsope:
http://planetuning.infillplane.com/h...ron_study.html

You can see two important wear bevels. One on the upperside, and one on the clearance side. You can also see how the very edge gets rounder and retreats from its original position.

The upper side wear bevel forms quickly and gets deeper over time. It's length and depth depends on cutting angle, capiron position and grain angle. It is caused by the shaving flowing over the steel. When you look at it with a microscope you will see that it is highly polished. Also because it scoops out steel from the upper side of the edge, it tends to keep the rounding of the edge quite small, which is called a self sharpening effect. The wear bevel in itself doesn't effect the cutting in a handplane. And because it is highly polished, it doesn't really need to be removed.

The clearance side wear bevel is a convexity. It forms slower but grows steadily over time and tends to lift the blade out of the wood. This is detrimental for the cutting action of the plane after a while.

So the practical issue is mostly the clearance wear bevel, the roundness of the edge and the burr that forms while sharpening. The whole idea from Beech with his jig and three sharpening bevels on both sides is overkill. Just sharpen the bevel side of the iron as usual. Flip the blade over on the polishing stone and remove the burr. Then you are done. That's how it works on a bevel down plane.

A bevel up plane has the bevel on the wrong side, in theory. The all important clearance bevel is on the face side of the blade, so it needs more effort to remove. But I'm sure you'll manage without jumping through too many hoops.

Always remember, people have sharpened steel edges for a very long time, and somehow got sharp enough tools to do some amazing work, even before all the modern sharpening kit was available. Keep it simple, do it often, that's still a good strategy.

[Derek Cohen]

A wear bevel is present on both BU and BD planes, and it needs to be removed from both. A sharp edge is created by smoothing both sides of the bevel.

Use the Ruler Trick for BU plane blades. It places a micro bevel of about 2/3 of a degree at the precise spot where a wear bevel occurs. In other words, you can hone it away. The tiny back bevel is not going to affect clearance angle in the least.

I agree with Kees that three bevels is too much effort. With BU planes I hollow grind at 25 degrees and then add a single desired secondary micro bevel to create the desired cutting angle.

Regards from Perth

Derek

[David Weaver]

For practical application of a three bevel system, it's really two bevels below the grind and it's scarcely different than a single bevel below grind, the very last polishing stone is just biased a little bit to make sure it works the edge.

Anyway, for practical application, Charlesworth's DVD is tops (and doesn't use any guides that are expensive or a nuisance - just the eclipse guide). David uses the method on chisels, too. I don't. I don't really use it on anything, except once in a great while when wanting to be absolutely sure an edge does not chip out nor dig in at the corners when smoothing. It is bona fide, though - it leaves 10 degrees of clearance on a bench plane and it leaves a final bevel at an angle where no common alloys will microchip and leave lines on a piece.

You may use the ruler trick charlesworth suggests to completely remove wear - anything more is overkill. Just don't use it on chisels.

Sharpen the japanese chisels with a single bevel - at least that's my advice - they are intended to be used that way, though a wet wheel grinder is OK if you have one and want to use it to grind. Cosmetically somewhat offensive, but structurally fine. A long thin primary and a steep microbevel is, however, not fine. Any microbevels if you insist on using one should be little different than the primary bevel.

[Derek Cohen]

Any microbevels if you insist on using one should be little different than the primary bevel.

David, honing directly on a hollow grind creates a coplanar micro bevel. I would argue that generations of woodworkers have done just this. Are you saying that there is a problem?

Regards from Perth

Derek

[David Weaver]

No. That's applicable strictly to japanese chisels.

Flat bevel or directly on the hollow is fine. The reason I made the comment above was to guard against long primary bevels on japanese chisels with steep microbevels because the makers don't design the chisels expecting a long thin primary on the hardened steel (hagane) - they expect that the hagane will be supported by whatever is laminated to it.

This is less of a problem on western chisels, obviously, though the same thing may apply on chisels old enough to be laminated and that are also hard.

[ian maybury]

Ta guys, that puts the multi bevel stuff to bed. It sounds as though it's not hard to overcome any issue by taking a bit more time to make sure that the final polish goes right to the edge - which is what I've been doing so far. Steve Elliott's pages are nice and clear and to the point, thanks for the link K.

I'm a fan of David Charlesworth and have a compilation of his mag articles in book form. Sounds like it's safe to follow his advice and break out the ruler to polish the flat side even on the bevel up planes Derek - I've just flattened them so far.

I've only lightly touched up a few of the chisels so far David, but it'd feel all wrong not to run with the single bevel on what after all are Japanese items unless it was to turn into a major time waster - which seems unlikely. (I've skimmed Odate's book and seen that the single bevel is the way it's done) I'm not that terribly time sensitive anyway.

David Charlesworth doesn't seem to mention using anything coarser than an 800 waterstone or equivalent when flattening backs. I have a 1000 Shapton. Below that only an untried 120 (which is recommended by Shapton for 'grinding' but it might be coarse for back flattening?), and a selection of diamond options in between. This may just be my fussing unnecessarily (being cautious for fear of doing harm to the backs that's not easily recoverable) but does anybody have any ideas on how coarse is it possible to go without running into problems with scratches that won't come out with successive finer grits when flattening the backs? (the primary bevel isn't really problem as it's not hard to cut it back to remove pretty much anything)

ian

[David Weaver]

Ian, I've always gone from either 100 grit loose diamonds directly to a shapton 1k or from 80 or 100 grit norton 3x paper to a shapton 1k. It seems like a big jump, but the shapton 1k is more like an 800 stone and it's aggressive cutting. Bias your pressure at the edge, and the bigger deal from one level to another has more to do with any dubbing that might occur on the coarsest grit (or if the coarse stone is out of flat) than the groove depth.

Charlesworth does prepare an iron back in his video using the king 800 and nothing more coarse. Older used irons sometimes demand stronger medicine than that.

I agree on the japanese chisels. I know derek tormeks them, and that's fine, but I am so smitten with how nice they look sharpened on a flat bevel with natural stones that I can't bear anything else. The only real nuisance occurs if you use them for really heavy work (i mean like abusive) and they chip. The only place I've had issue with that is chopping plane mortises, which is fairly abusive until you get the feel for doing it quick without being hard on tools.

Cleaning shoulder lines with a parer is something else that's very hard on the corners of chisels (if the wood is not soft), ....but anything else should be a matter of sharpening very little.

[Daniel Rode]

FWIW - Rob Cosman appears to use tri-bevel sharpening. The secondary bevel is at about 5 degrees more than the primary and a final bevel another coupe degrees steeper but only on the finish stone. He also uses David Charlesworth's ruler trick/ back bevel (As do I). Sounds a lot like what David described to me.

As I understand it, when resharpening, he works the iron at the secondary bevel angle until he raises a burr. As far as I can tell this erases the tertiary bevel entirely. Then it get's reformed each time on on the finish stone.

I can understand how this would work but I'm not sure why this would be better than just working the secondary bevel on the finest stone.

[David Weaver]

Charlesworth's DVD came out a long time ago. Something like 2000? Cosman's method is otherwise identical but with a little hardware gimmick (and I don't mean gimmick in an offensive sense, the entire woodworking hobby is a combination of gimmicks old and new). The minor differences (in how the camber is set, etc) don't amount to much to me - I sort of wonder why there was a need to go to a three bevel system freehanded, and do it differently (for beginners) than charlesworth other than to claim a method as one's own.

Charlesworth's is the method that is probably going to be most frequently used with absolute success by someone the first time they do it. It's nice to have when you intend to have one plane set up for perfect final smoothing (as in a plane set aside that doesn't leave tracks and doesn't chip out).

Charlesworth's method erases the tertiary bevel, too - and the tertiary bevel is very small each time you make it. It's erased with a medium stone because it's much easier to remove the wear with a medium stone. It's a nice method, works really well in practice for irons that don't have too much camber and only requires about $12 of hardware.

[Warren Mickley]

I use a single flat bevel. I start with a coarse stone every time I sharpen in order to get past the rounded edge; I think this is the most efficient way. I think it is best to use the same routine every time and to sharpen at the same stage of dullness. The back needs to be abraded regularly, not so much for wear as to work the burr and to polish out the scratches which accumulate with use. The ruler trick seems like an idea for a guy who is constantly trying out new plane irons, but it is not necessary for day to day woodworking. I have only used about nine plane irons since 1970 for my bench planes.

On the bevel, the scratches from the coarse and intermediate stone have to be removed during the refinement stage of sharpening. I think this is faster and easier if the stones are not too harsh. The best way to determine if the effects of coarse and intermediate stones have been polished out is by gauging the performance of the tool. This takes experience and careful discernment.

I got an email from Brent Beach in 2007 asking if I would detail my sharpening methods. I spent about an hour writing a note to him. His response was very dismissive of my methods and he failed to even thank me for my efforts to organize and present my thoughts. I don't think he has much experience in real woodworking.

[ian maybury]

'I am so smitten with how nice they look sharpened on a flat bevel with natural stones that I can't bear anything else.' That's about how I feel about the chisels too David - the question was to check it out in case it meant missing out on anything much.

It sounds like you are saying that there's no great problem re. removing scratches left by a coarse stone or whatever used to flatten the back provided care is taken to work back up through the grits, and that I'm probably OK with the stones I have which is great. I've just noticed that Derek C's sharpening page suggests much the same. You are also suggesting that the real risk (because it cuts fast/removes lots of metal and wears quickly) is that a coarse stone can quickly do harm by rounding the back if it's not religiously kept flat.

It all seems to point to it making sense to start back flattening with the finest stone that seems likely to get the job done, and to only back down into coarser grades as they seem to be needed. (as Warren says) Which explains David Charlesworth's starting with the 800 grit too.

The edition of the book of his mag pieces that I have which describes the ruler trick is by the way © 1999.

To Daniel and Warren. My essential inclination (presuming it survives further contact with reality) is as yourselves and the other guys - to trade a bit more honing time/stone wear/metal removal for a simplified sharpening procedure. i.e to run with the fewest bevels/simplest sharpening process. Provided it doesn't mean missing out on a significant benefit delivered by using more bevels. To be fair to Brent B though he fairly clearly says that it's always possible to sharpen with a single bevel and a flat back (or with two or three bevels) - it just requires cutting the final bevel(s) back far enough to eliminate both wear bevels. The risk he seems to point to is that it's possible to hone e.g. the primary bevel to the point where a wire edge forms, but find that this was not far enough/that the plane still performs badly because the wear bevel has been left intact on the back side of the blade.

The essential justification that I picked him up as putting forward for his multi bevel method is just that it minimises blade wear/waterstone wear/sharpening time… Sounds like depending on taste that there's multiple options available..

Thank you all very much for the input, it's been of great help. Tomorrow is a big sharpening day….

[Jim Matthews]

Do you test for raising a burr, as you add bevels?

I was under the impression that the wire edge is an indication that you're
close to the keenest finish you can get, on any given piece of steel.

[ian maybury]

I'm only repeating what i have read Jim, but it seems to make sense. Go to 'Bevel up Planes' near the bottom on this page by Brent Beach: http://www3.telus.net/BrentBeach/Sharpen/bevels.html The bullet point 'The green line….' describes the issue - which seemingly can arise on a bevel down blade too.

To try to explain - it's not the clearest ever. What he seems to mean is that normal wear/blunting in use results in quite a rounded edge/extremity to the blade, with longish wear bevels extending back from both sides of it. (especially on the work facing side) Putting a micro bevel on one side or the other of this edge alone will cause a misleading wire edge to form once enough metal is removed so that the rounded extremity is removed - because once that point is reached the edge thins and hence bends. The trouble is that at this point much of the wear bevel on the other side of the blade (the side of the blade pointing downwards forms the widest wear bevel, and this is the one that causes the greatest reduction in performance - it reduces the ability of the blade to penetrate the wood so that it 'skids') is still largely intact.

He seems to be saying that it's necessary to keep on honing through/until this second wear bevel is also removed in the case of a single bevel sharpening. Or alternately to remove it by honing enough of a (second) micro bevel on the second side in the case of a two micro bevels job) Either way until a sharp edge is formed by the meeting of two finely polished flat surfaces.

He suggests that this entails removing quite a lot more metal than many do when they sharpen (especially in the case of a single bevel - up to 0.003in - which is why he proposes his multi bevel method to save time and metal removal), and that the commonly resulting partially formed edge is a frequent cause of lost performance. (the problem doesn't arise on a fresh blade/first sharpening where the wear bevels haven't yet formed, or are very short) Since testing for a wire edge can be misleading his test of sufficient honing seems instead to be visual - keep on going until (viewed through magnifier) the wear bevels on both sides are no longer visible/have been honed away. That's whether from one (single bevel sharpening/chisel) or two sides. (two bevel sharpening/plane with ruler trick) This problem of premature wire edge formation arises with both bevel up and bevel down blades.

Clear as mud - hope it's correct...

ian

[Warren Mickley]

Yes, Ian it is possible to feel a burr before the wear bevel has been completely removed. But this is more likely to happen if you wait to sharpen until the tool is quite dull, or if you only hone on fine stones or a strop as a stopgap measure. Less likely to happen if you begin with a coarse stone every time. Also less likely to happen if you have just been using a tool and can sense how dull it is and how much burr you need to feel to be confident. Also if you are used to the tool and the timber you are working you can sense when you have not quite gotten the best out of sharpening and do better the next time. You can feel it if you do not quite remove the wear on the back.

This is why it is helpful to work with a small, core kit so that you have intimacy with your tools. And to go through the same sharpening routine every time rather than some petite sharpenings followed by some grand renewal. If you pile up eleven planes that need sharpening, it is hard to remember how each was when last used, when it was last ground, how it reacted last sharpening.

I think that if you need to remove .001 inches to sharpen a tool, you waited way too long.