A profile that works better on chisels

[D_W]

I've got several nicely shaped chisels that just aren't that good (robert sorby, most notably, but also some older buck brothers).

It occurred to me that some of the things that work well on knives may also work well on chisels, but until recently I didn't pay enough attention to really figure it out. I can also reharden chisels (handles on and all), so it's really not that much of a priority.

But I decided I'd try the knife bevel thing (determining where an edge fails and eliminating only that, and not overstrenghthening anything else because it'll increase cut resistance - in chisels, this is cut and wedging resistance, though I suppose knives are the same).

what I've come up with is this:
* at 28 degrees flat bevel, my sorby chisels don't hold up well. Actually, no chisels that I have will really hold up well.
* I've come to figure out with experimentation that I can use a buffer to apply the final bevel to a very very tiny part of a chisel bevel and get far better penetration from the chisel, and edge holding that is monstrously better

Pictures of this edge are as follows (targeting 28 degrees, came up around 27.2 - flat microbevel on a 20-couple primary).

Here's what this chisel looked like after malleting two socket's worth (halfblinds, more or less) of smooth relatively easy working american beech:

These pictures are the same magnification - about two hundredths of an inch from top to bottom.

And here's the profile that solves this better than I expected - you are seeing the secondary bevel only at 23 degres, and the last 5-7 thousandths has been rounded over with a buffer just a little.

And here's what the back of the chisel looks like through the same wood (though at 1" wide, it actually took less in terms of mallet striking power to get this chisel through beech than it took the 28 degree chisel at 3/4ths wide). Fewer strikes and with less striking power.

I'd done a fairly poor job of preparing the back of this second chisel, but the reduction in edge damage is striking. Even if I'm not!!

I'm referring to this sharpening method as "the unicorn bevel", because we're often chasing unicorns in woodworking. In this case, it's finding a bevel that penetrates wood with less resistance, but holds up much better.

You can see where the damage usually occurs - it starts in the first couple of thousandths of the edge, and then as it gets deflected or chips, things go downhill from there. If we can prevent it from the start, things proceed far better.

The overall setup of this edge is something like follows
*20 degree primary
*23-25 degree secondary (just as any other microbevel method is applied, if the second bevel gets too long or steep, just regrind
* buff the very tip for about 5 seconds cotton buff then, 8 stitched, on a very cheap buffer (you have to experiment a little bit until both goals are met) for about 5 seconds with calcined alumina bar around 5 microns. none of these details are vitally important, but the finish level from the 5 micron stick on a cotton buff is about as good as 1 micron abrasive, maybe better (the buff doesn't have enough strength for the abrasive to really dig in).

(that's the finish left by this fairly coarse buffing media - most of the lines are just light oil - it's really hard to wipe that off until it's gone at this magnification level).

For comparison, here is an edge from a black dan's arkansas stone with a polished honing surface.

The sharpening cycle time for this is about 30 seconds, even with some edge damage (you can still just abuse the chisel needlessly and damage the edge further up than the modifed area, but that's kind of dumb).

With this method, we have very simply done the following - removed or modified the very tip of the chisel where failure starts and propagates, and then taken advantage of the ability to narrow the edge behind it because that's not really where failure occurs, so why increase the amount of work done and wedge wood with it?

not just great for chopping, but also supreme for paring chisels. The cutting ability of this edge is as good as anything I've ever used sharpened any way I've ever sharpened. It's incredible. For those who keep a filthy shop as I do, nothing ever seems to stick in the buff and contaminate it, either.

 

[D_W]

two things of note:
* the test chisel with a flat microbevel was honed on both sides to 1 micron diamond on corian, so it's not for lack of sharpening.

* this profile as shown above isn't for common pitch planes. It's great for knives and chisels, but not enough clearance on plane irons.

I'm just getting around to experimenting with a lower starting angle and then buffing more lightly for plane irons, but I don't think there's really a great reason to chase this for planes as they don't generally fail by the kind of impact shown on the chisel images above, and chisels don't take much back-side wear, while plane irons take a lot (and it needs to be removed on a stone).

Here's a full sharpening cycle on the buffer method (except the grind, which is only done every 4-8 times you hone).

https://i.imgur.com/OgtFRzJ.mp4

 

[mathias]

A couple of things:

The 1micron diamond/corian: how precise is it (what are the spec/tolerance ? What does the finished surface look like?)?

Is the buffed angle really the same as the diamond/corian because when I make a cutout of the 27,2 degree angle and put on the photo of the buffed I get the result that the buffed angle is bigger.....

 

[D_W]

Hi - the 1 micron diamond is extremely closely graded. Here is a picture of the back of an iron finished with it:
https://i.imgur.com/I3miSbE.jpg

(most of the dirty looking stuff in the picture is actually oil. AT this magnification, it takes a lot of wiping to get all of the oil off. If you wipe a chisel with your shirt, your shirt now has more oil on it than this picture has, which explains why chisels that have been wiped off still have corrosion protection).

So, the top picture is just a microbevel. that's not what you want to do with diamond on corian.

the second picture is the buffer and you want to imitate what the buffer did when you use diamond on corian by hand (so roll the very tip a little bit, but nothing remotely close to a full rounded bevel like paul sellers suggests).

The desirable part here is that the very tip of the straight bevel is what fails. We remove it, and then make what's behind it less steep because that's not where failure occurs paring or chopping dovetails).

The scratches on the side of this chisel are from a fine oilstone, so you can compare those to the fineness of the diamond and buffer pictures to see how absurdly fine they really are.

 

[D_W]

this is for paring and chopping, it's not for chisels that get prying or twisting (mortise chisels). The reason for that is when you pry and break an edge on a mortise chisel, it's going to be past the modified part of the edge. Plus, there's no great reason to chase a shallower and shallower bevel on a mortise chisel because the short fat bevel on a mortise chisel is what allows wedging to break chips from the side of a mortise and then pull them loose when rotating the chisel. If you put a long really flat primary on a mortise chisel, you lose both of those.

It may be hard to see what the virtue is here, but I am going to do a test with some marginal chisels and a V11 chisel (when it arrives) and I suspect that the marginal chisels sharpened with this method will go through material just as easily (or more easily) than a V11 chisels honed to 28 degrees flat bevel, and will hold up as well.

That's kind of a shocking result. sharpening for 30 seconds 1/4th as often is also nice, as is being able to use a marginal chisel that you really like but don't like the edge holding on (steepening the entire bevel or putting a large microbevel on it just makes it feel blunt - this doesn't).

 

[mathias]

I understood that the diamond/corian (first picture at 27,2 degrees) didn't hold up as well as the buffed edge (picture 3). Is this not the case?

 

[MikeG.]

I'm not sure what is with your Imgur link, DW, but the second photo I saw was of a couple of gorillas and a couple of park rangers.

Could you please describe the physical set up of the cotton mop. Is this a spinning wheel in a pillar drill or bench grinder, for instance, or is it some sort of manual set up? Is this important anyway, in your view, and couldn't the same result be achieved on leather? The same shape could be, surely. Therefore, is your primary claim about the angles (I've got some "evidence" to back this up)*, or is it about the sharpening media? I always find that latter stuff distracting, and can't differentiate your claims from your methods.

*For many years I just sharpened stuff. If I got a decent edge, I didn't care what the angle was. Over time, all my chisels tended towards angles which were significantly smaller than the ones which seem to have become set in stone these days (25 primary, 30 secondary). I would happily do heavy work in seasoned oak, bashing a 1-1/2" chisel with a big mallet, with a primary angle which turned out to be under 20 degrees when I finally measured it (as a result of joining this or another forum and finding that people thought angles were thought important). Edges lasted ages. Stupidly, I reground all my primaries to 25 degrees, and have regretted it ever since. I can't bear the thought of removing all the steel necessary to get them back to where they were......

 

[D_W]

So, the whole idea here is to do all of the geometric setup before getting to the buff. Long primary like you grew to prefer in your past - it's less work, right? Now you've got regret. Secondary just above the primary (+3-5 degrees). That keeps everything controlled and straight. The last part is most easily done with the buff because it rounds the edge over a little bit, doesn't create too much heat and there's no wire edge. So the typical sharpening cycle as shown in the quirky video (imgur often has database and linking issues) is 30 seconds. Refresh the primary part, buff the edge.

It could be done with anything. I've tried leather, freehand, etc. It all works. Buffer is just the easiest and buffer wheels with wax compound seem to free themselves of contaminants. Leather can create a heat problem, and its ability to launch a chisel for a beginner is potentially problematic. I found heat and too strong of a cutting action to be the issue.

I'll try the imgur link again.

This is a subtle thing that I'm sure has been done by knifemen and carvers quite often. It makes a longer lasting edge and less work for the user.

https://i.imgur.com/OgtFRzJ.mp4

 

[D_W]

interestingly enough, I mentioned this buffer deal on another forum. I don't set angles for grinding and assumed my chisels were around 25.

One of the posters requested measurement of everything here (the microscopic edge is obviously difficult to measure, but the primary and secondary are pretty easy).

I guessed way off and the angle that laziness (efficiency) had brought me to over time on the primary for a sorby chisel was 19 degrees.

Edges kind of hold up (if a single bevel is used) in hardwoods at 28 degrees. They often don't, though. A hollow ground angle that's approaching 30 degrees is not pleasant to use, and the very tip of the edge that takes the damage will still take the damage. The advice that's been given as long as I've been on the forums is "then it's time for a better chisel"

When a better chisel doesn't stand up to the work (like mortising plane bodies), then it's time for a better chiseler (or sharpener).

 

[D_W]

I redid this test just to confirm the results.

This time, I used apple for a specific reason - I have an offcut just under 3/4ths inch wide, which means I can use the sorby chisels to cut it without holding wood on the side.

First test, same chisels (unicorn 1 inch, 28 degree 3/4ths inch) using the edges shown in the angle pictures (not resharpened, etc). flat bevel is 1 micron diamond, unicorn is yellow stuff.

83 strikes to get the flat bevel chisel through the apple, 60 to get the unicorn chisel through the apple:

edge damage to the flat bevel - 3/4 inch sorby:

This apple feels a little bit harder and drier if that makes sense vs. the beech billet. The edge failure is much more uniform in it. If you check this chisel with your finger, it feels like a wire edge has been raised (a small one, but you can easily feel it.)

1 inch chisel - unicorn edge. No visible damage. It's hard not to tap the mallet more lightly even from the start as it gets through the wood much more easily.

Next, swap the chisels, unicorn the 3/4th chisel and flat bevel on the 1 inch chisel to make sure it's not the chisels and lack of consistency. (i've never perceived much variance in three sets of these chisels, but you have to check and make sure it's not also related to a bigger chisel transferring more of the mallet energy).

80 strikes with the flat bevel, 55 with the unicorn. I paid a little bit more attention to not let off of the striking pressure since the unicorn was getting through the wood more easily.

28 degree bevel, 1 inch chisel:

Then, the 3/4th inch chisel unicorned:

I'm not sure if any of that is minor edge damage.

I drew 11 sections in each inch of malleting here. Again, wood narrower than the chisel width so no holding wood.

(actually, i can't remember if it was ten sections or 11 in an inch, but it was the same each time).

I have the feeling that I will be able to reproduce this test over and over and only in the case where the wood is so tolerant that neither edge gets damaged will both hold up equally well.

There is certainly a case that you could continue to raise the flat bevel angle, but i can only say why? It just becomes less and less easy to get through the wood compared to this "unicorn" method.

If I were only using a flat bevel, I would increase the angle for one reason - it takes a while to hone this much damage out of a chisel, and I didn't manage to do it the first time I switched the 3/4" chisel from flat bevel to buffed even though I spent a fair amount of time honing a pretty significant wire edge on the chisel (but shallow, our secondary is something like 23-25 degrees).

This method is demonstrably better than what we have been taught for a long time (that two edges must meet from two planes to have a truly sharp edge). This slightly steeper rounded initial edge and shallower backing behind it is far better.

 

[D_W]

for my next party trick, I'm waiting on a new 1 inch PM V11 chisel and will see if I can set the inferior sorby chisel so that it will outperform any flat bevel on the $105 V11 chisel.

If it passes that test, then I think spending $50 on a generic buffer and another $10 for a wheel that works well with this (perhaps 10 more for a buffing stick) is a far better idea than buying expensive chisels.

And using expensive chisels with this method is far better than using guides and creating flat facets on bevels.

Refresh time for sharpening with the 1k diamond hone to the buff remains at 30 seconds. Never more needed for any reason.

 

[MikeG.]

Just whilst I am enjoying the novelty of agreeing with you, DW, I'll say that the way I strop my chisels produces this semi-rounded end. I make no attempt to keep the chisel at or near the bevel angle when stropping. I have a strop which must by 16 or 18" long, and at the start I have the handle low, and by the time I have drawn the chisel the length of the strop it (the handle) is raised right up. No idea of the angles involved, but if someone said 15 degrees to start with up to 65/ 70 degrees to finish, I wouldn't argue. My empirical route has arrived at much the same point as your more studied method, by the sole expedient of being easy, repeatable and effective.

 

[D_W]

That is what I did for a while before starting to use the buffer (which is a bit lazier, and the buffer does a magic trick with fairly coarse abrasive, leaving a mirror polish with it).

I referred to that as a round over and it's generally met with "that's just the sellers method".

No, it definitely is not, just as you have found.

I would bet that in the days of paid hand work, this was quite common - it's hard not to notice how much easier and better it is. I'm not surprised that you came to it also.

I also wrankled feathers a couple of years ago by suggesting a tiny roundover on a japanese chisel makes for a far better performing chisel, and you cannot talk about subtleties with japanese tool fans. It's almost like kicking a nun to mention that you did anything other than hone a full flat pane on the world of internet japanese tool experts (the antique japanese chisels that I've pulled out of japan often have some type of bevel that gets steeper at the very edge, though - they chip instead of showing the deflection shown in these pictures - but they don't chip with the "unicorn".

Thanks for your input.

 

[D_W]

A follow up to this. I've done a bunch of testing. That's all fine and good. Things don't really get real until someone else does testing in a test that would seemingly be hard to get through and gets the same results.

Winston Chang over here in the states has duplicated what I've described and shown to some degree. To test how well this works, he's applied the method to buck brothers (hardware store relatively soft chisels) chisels. He ran a test before doing it with normal sharpening, and then after, and he has nice color scope photos of the edge and some commentary.

https://chisel-chop-test.netlify.app/

That's his page. He's using the buff wheel on a simple cordless drill, rounding/buffing only the very tip. The top segment of pictures shows normal failure with a flat bevel and the bottom shows the same test through hard maple and the buffed edge. Nearly no damage.

I'm not sure if I showed sharpening cycle time with this, but I made an imgur video segment (no sound) of a full sharpening cycle with a chisel. This chisel is used and not freshly off of the grinder (it's not just the most ideal situation).

https://imgur.com/OgtFRzJ

Just after this freshening, the chisel outperforms anything I've ever seen anyone do by hand. Winston is now at the point where his edges are also subjectively sharper than his hand sharpened edges, on top of the additional durability.

Winston is a japanese tool user and his sharpening fanaticism matches it (not uncommon for japanese tool users to have some kind of setup to check the accuracy of their sharpening). Within a week, he's able to better what he's spent a long time perfecting by hand.

Hard maple is used directly across the grain as a reasonable test (These chisels will fail in cherry, but some better chisels like AI will not fail that quickly in cherry most of the time unless the angle is acute). For the folks who haven't worked hard maple over there, it's only slightly harder than european beech, but it is for some reason more resistant to being wedged and severed, and makes a lot of friction. When planing, it also makes a lot more friction and for reasons that I have no clue about, is not much more dent or wear resistant but is a lot harder to plane. When you pick the shavings up (equivalent thickness) its tensile strength is a lot higher than beech. Enough so that I burned out a leaf vacuum that i use to pick up plane shavings in my shop.

I didn't request anyone test something goofy like gidgee or verawood because then the work becomes ghee-whiz type of BS that leaves behind the question of whether or not it's relevant.

 

[mathias]

I'm still not 100% what you are comparing.

As I read you prepare two chisels exactly the same way and then you add a buffing that rounds the bevel a little to one of them?

 

[MikeG.]

No, it's the principle angles. A primary bevel of 20 degrees. That's the difference. It's well worth taking a secondary chisel from the back of a drawer where it's lain unused for years, and sharpening to 20-ish degrees, and seeing what you see. As I say, mine were like that before I joined a forum and found that there was an angle they were "supposed" to be....and they were better then than now.

 

[D_W]

Mike is right.

I did have a shallow primary on both of these, but the difference is the use of a "pointy" flat facet as the final angle. You can substitute this mostly for any kind of flat edge (including full single bevel or hollow ground at the final angle), except that it may outperform the full bevel methods due to less wedging resistance.

but it still underperforms the rounded edge.

The connection that I didn't make in the past (I also have gotten older chisels with a very long shallow primary, but the secondary edge is quite tall - which negates some of the penetration.

The thing I was chasing was this:
* you can already just add a small secondary and tiny tertiary bevel to 20 degrees and get better performance. The angle of the tertiary bevel will need to be solved (what's necessary for you to not see damage). In maple, it 's something >32 for the sorby chisels and it's 32 for the AI chisel
* if the secondary angle is something like 23 or 25 and the tertiary is 32 or 34, then the tertiary bevel should be tiny. That's all that's needed to remove the problematic part - it doesn't need to be a big shiny bit to be strong unless you're prying - prying a lot.

The secondary bevel is used to keep the tertiary tiny, the primary grind is shallow to make it easy to refresh the secondary angle a few times, else you have to grind more often.

And then the final point was this - if you replace the tertiary angle with a few seconds of time on a cotton buff with some spine instead, it beats any flat final bevel, micro or not. That tiny rounding slips through the wood more easily than a flat facet and holds up better. I'm guessing it holds up better because the very tip where damage starts is gone, but it's still not particularly blunt other than that.


If all of this is confusing, set up two chisels - one as I mentioned:
* 20 degree primary 23-25 secondary and buff just until a tiny bit is buffed
* another with a faceted microbevel, any way you want to do it, but the final bevel needs to be 32 or more depending on the quality of the chisel, or it won't hold up with the first. If shallower and the edge starts to fail, then the thinner edge actually becomes less efficient if you continue on - first order of business is to prevent damage

Then chisel something with the two, inspect for damage. The performance difference between the former and the latter is large. The former has less resistance by a lot, and it holds up better in work, too.

 

[mathias]

So then you are comparing two different angles then, right?

If so, then sure the buffed one will hold better/longer. What if the unbuffed one is sharpened to the same (estimated) angle as the buffed one?

 

[MikeG.]

I think what DW is saying is sharpen your "ordinary" chisel any way you like and compare its performance to that of the 20 degree+secondary+rounded chisel.

 

[D_W]

So then you are comparing two different angles then, right?

If so, then sure the buffed one will hold better/longer. What if the unbuffed one is sharpened to the same (estimated) angle as the buffed one?

OK, angle isn't that easy to narrow down. Here's the buffed chisel:

https://i.imgur.com/wyoqb4H.jpg

23 is the secondary angle, the buffed bit there is shown, and the drastic part is a couple of thousandths long.

Mike is right. Don't worry so much about angles. The very tip of this chisel is probably steeper than 33 degrees, I don't know. But rather than try to figure that all out, do your best with your own method and then sharpen one like this and compare.

It's impervious to normal damage in maple (even though it's soft and doesn't hold up even with a microbevel of 32 - it would probably hold up at 34). The behavior of the chisel is substantially sharper feeling and takes much less effort to pare or mallet than even the 32 degree microbevel let alone the 34.

I didn't want to measure all of these things ,but the instant I put this up on wood central, the question was "how can I duplicate this making tiny microbevels instead". The answer is, it doesn't appear that you can. I think you could train yourself to round the tip over like this with a whole lot of physical effort on some kind of strop, hard (rolling the edge) or soft (leather with many many passes, or conceding some fineness).

Here in the states, this buffer can be had for $39. It turns out it makes a better edge than I can by hand, and then completes the stropping at the same time. All that I need to do is spend about 15 seconds on a diamond hone and then buff the edge. Once every 3 or 4, i refresh the grind, but the action of doing this sharpening and then using it is more important than narrowing down the microbevels.

As a trial, I put a 34 degree microbevel on an ashley iles chisel (a better chisel, which for some reason cuts with the buffed edge even better than the sorby - marginally, but you can feel it). Same idea as this but for the folks who don't have a buffer, literally 4 strokes on a cast iron lap with 1 micron diamonds. I would've been surprised before, but am not now, that even that tiny microbevel on a 23 degree secondary held up well. BUT, it still took a 25% greater number of strikes to get through the same volume in the same test piece and the cutting characteristics were substantially different.

I did try rounding the edge over on corian yesterday with green chrome ox wax stick - it's slow. I think diamond on cast would do it better, but that does require a little stropping. If doing anything by hand, at this point, I would try to find some way to duplicate what the buffer does rather than steepening a microbevel until the edge holds up - it just doesn't work as well as the buffer does.

I would normally be agnostic about equipment, but thus far, the buffer is well worth the $39 and it negates the need for an expensive finish stone (the backs of plane irons can be worked on a middle stone like a washita). No clue what the markup is on the same buffer in the UK, though - there are industrial supply places here selling the same machine with their name on the tape instead of the made-up harbor freight brand and they're between $125-$150. If that's the case over there, this becomes less trivial.