Hesitate to ask a sharpening question

[Prashun Patel]

Brian-
We've been through this in person before, and I still struggle to find the burr. I can easily raise, feel, and remove burrs at the very rough grits ( < 1000) when I am establishing the primary bevel. But as soon as I move up to the 1000 grit stone, and hone free hand, I can no longer feel a raised burr.

Last night, I hollow ground two chisels on the grinder. I honed 2ndary bevels at 1000, 5000, and 8000. With one, I free-handed. With the other, I used a guide. On both, I did as you counsel (do the bevel, work the back). I could not see nor feel a wire edge on either. I see the faintest glimmer of something under a loupe at the edge which I swear is just light. But I certainly can't feel it, and when I work the back a little, it doesn't appear to disappear. Both chisels feel sharp and appear to work well.

Is the wire edge raised on the finer grits, by hand, far more subtle than the one raised at the rough grits with power?

Do you other guys have trouble raising/feeling a burr with the finer grits?

Does anyone have a good close up picture of what a burr would look like after say 1000, 5000, and 8000?

[Malcolm Schweizer]

Just FYI- I was serious in my first comment about offering to sharpen an iron to 15k for you if you want to see the difference.

[Robert Hazelwood]

Brian-
We've been through this in person before, and I still struggle to find the burr. I can easily raise, feel, and remove burrs at the very rough grits ( < 1000) when I am establishing the primary bevel. But as soon as I move up to the 1000 grit stone, and hone free hand, I can no longer feel a raised burr.

Last night, I hollow ground two chisels on the grinder. I honed 2ndary bevels at 1000, 5000, and 8000. With one, I free-handed. With the other, I used a guide. On both, I did as you counsel (do the bevel, work the back). I could not see nor feel a wire edge on either. I see the faintest glimmer of something under a loupe at the edge which I swear is just light. But I certainly can't feel it, and when I work the back a little, it doesn't appear to disappear. Both chisels feel sharp and appear to work well.

Is the wire edge raised on the finer grits, by hand, far more subtle than the one raised at the rough grits with power?

Do you other guys have trouble raising/feeling a burr with the finer grits?

Does anyone have a good close up picture of what a burr would look like after say 1000, 5000, and 8000?

If you are checking for a burr by running your finger off the edge on the back of the blade, that only seems to work well when the burr is pretty large, like you'd get off a course stone. On finer grits, I don't check for the burr directly but instead just check the keenness of the edge with my fingertips. With experience I know when it feels sharp- if it doesn't feel sharp then I either did not do enough work on the coarse/medium stones (i.e. did not create new edge), or there is a burr left. Light, alternating passes of the bevel, then the back, with edge leading strokes seem to be the most effective. Increasing the honing angle slightly for these burr removal passes is also very effective. After a bit of this I'll recheck with my fingertips and typically there is a substantial improvement in sharpness. If not then I probably didn't do enough work on the coarse/medium stone stones.

[William Fretwell]

At the finer grits it is not as clear cut as burr......burr gone. In my case it feels more like rough sharp then noticeably smooth sharper after working the back of the blade flat on the 8k stone. After stropping the bevel it feels sharper again. The edge will 'catch' more noticeably. After this discussion I will cease moving the back on the strop, even flat, and see how that goes.

The real test is during prolonged planing, does it last longer, are you 'polishing' the wood? When does polishing the wood change to cutting the wood. When cutting gets harder feel the blade again, the word sharp does not even enter your mind. I can just strop the bevel and it restores 'sharp'. That sharp is shorter lived but a very quick fix and worthwhile for hogging off. The next sharpening is a few strokes on the 800x then back to the 8k and a quick strop.

[Prashun Patel]

Robert, I have been doing all this time as you do. I just feel the tip of the blade. I can tell when my blade is ready. That is to say, I can tell when I've gotten my blade as good as *I* can normally get it. This is certainly serviceable, and I am not a sharpening geek; I only want my blade to do it's job as well as it can do.

However, when studying with Brian, I see that his blades really are slightly sharper than mine. It makes the experience of paring and planing trickier woods slightly more easier and predictable. He has been able to feel finer burrs where I cannot. Since working with him this summer, I take care to work the backs lightly after bevel honing, but I still feel that I'm removing a phantom burr. I don't sweat it 9x out of 10 because my blades work fine.

Even if the burr is an elusive Holy Grail, just the sheer chase of it has improved my technique. Strokes are more deliberate and fewer than even 6 months ago.

[Stewie Simpson]

I can only comment on my own experience with using earlier type steels. I have no problem feeling a very fine burr using my fingertips, after working the cutting edge to 12000 grit. The remaining burr is then removed with 2 strokes on each side of the cutting edge, using a loaded leather strop.

Stewie;

[Stanley Covington]

If you can't feel the burr passing over the ridges on your fingers, try a different method. This one is not as quick a testing method as the skin on your finger, but it is more reliable.

Rest the cutting edge at a low angle on your fingernail close to the quick. The angle should be such that the cutting edge, not the bevel, is riding on your nail. To test that you have the right angle, carefully and gently push the blade while increasing the angle until the blade just starts to dig in. Increase and decrease the angle until you have the lowest possible angle where the blade will dig into your fingernail.

Slowly and lighty pull the blade straight back over you fingernail towards your fingertip. If the sensation is absolutely smooth, there is probably not a burr. But if you feel a scraping or catching sensation, that is a sure sign of a burr or some other defect in the cutting edge.

If you discover a burr, next test the same spot on the blade with the finger on your skin, noting the sensation, to train yourself to feel the burr.

This is easy with small blades, but hard with larger plane blades. Please be careful and do this only when kids or pets are not in the shop to distract you.

Stan

[Brian Holcombe]

Brian-
We've been through this in person before, and I still struggle to find the burr. I can easily raise, feel, and remove burrs at the very rough grits ( < 1000) when I am establishing the primary bevel. But as soon as I move up to the 1000 grit stone, and hone free hand, I can no longer feel a raised burr.

Last night, I hollow ground two chisels on the grinder. I honed 2ndary bevels at 1000, 5000, and 8000. With one, I free-handed. With the other, I used a guide. On both, I did as you counsel (do the bevel, work the back). I could not see nor feel a wire edge on either. I see the faintest glimmer of something under a loupe at the edge which I swear is just light. But I certainly can't feel it, and when I work the back a little, it doesn't appear to disappear. Both chisels feel sharp and appear to work well.

Is the wire edge raised on the finer grits, by hand, far more subtle than the one raised at the rough grits with power?

Do you other guys have trouble raising/feeling a burr with the finer grits?

Does anyone have a good close up picture of what a burr would look like after say 1000, 5000, and 8000?

The hollow ground blade will be the easiest for this. Go through your regular routine of sharpening, then when you are completed, return back to the finish stone. Work the bevel and before you work the back check for a burr (it is very very light as this point). That should help to improve your thumb gauge for checking since you will know it is there with certainty. Work the back again and see if you can feel the burr.

If you're seeing light reflecting from the edge, then there is still some wear left. When its totally gone you can't see the edge at all.

I'll take some photos next time I sharpen and see if I can highlight the wear, it may be quite difficult to do with an iPhone but it is surprisingly capable on occasion.

[Robert Hazelwood]

Robert, I have been doing all this time as you do. I just feel the tip of the blade. I can tell when my blade is ready. That is to say, I can tell when I've gotten my blade as good as *I* can normally get it. This is certainly serviceable, and I am not a sharpening geek; I only want my blade to do it's job as well as it can do.

However, when studying with Brian, I see that his blades really are slightly sharper than mine. It makes the experience of paring and planing trickier woods slightly more easier and predictable. He has been able to feel finer burrs where I cannot. Since working with him this summer, I take care to work the backs lightly after bevel honing, but I still feel that I'm removing a phantom burr. I don't sweat it 9x out of 10 because my blades work fine.

Even if the burr is an elusive Holy Grail, just the sheer chase of it has improved my technique. Strokes are more deliberate and fewer than even 6 months ago.

I suppose I have the benefit of never having experienced Brian's edges in person In fact I really don't know anyone in person who's much into sharpening or owns any stones beyond what you can get at the box store. So I am self-referencing, as you say.

My basic theory is that if stropping on bare leather noticeably improves the edge after the finish stone, then there was a burr of some sort remaining. If the sharpening is ideal off the finish stone, then bare leather stropping could only degrade the edge, or at least have no effect. The closer I get to this latter state, the better performance and edge retention I'm seeing. Switching this past summer exclusively to freehand sharpening, and to a translucent arkansas as a finishing stone, seems to be helping.

[Pat Barry]

If you can't feel the burr passing over the ridges on your fingers, try a different method. This one is not as quick a testing method as the skin on your finger, but it is more reliable.

Rest the cutting edge at a low angle on your fingernail close to the quick. The angle should be such that the cutting edge, not the bevel, is riding on your nail. To test that you have the right angle, carefully and gently push the blade while increasing the angle until the blade just starts to dig in. Increase and decrease the angle until you have the lowest possible angle where the blade will dig into your fingernail.

Slowly and lighty pull the blade straight back over you fingernail towards your fingertip. If the sensation is absolutely smooth, there is probably not a burr. But if you feel a scraping or catching sensation, that is a sure sign of a burr or some other defect in the cutting edge.

If you discover a burr, next test the same spot on the blade with the finger on your skin, noting the sensation, to train yourself to feel the burr.

This is easy with small blades, but hard with larger plane blades. Please be careful and do this only when kids or pets are not in the shop to distract you.

Stan

This is what works best for me. I find that the burr easily catches on the finger nail in this manner - not so much on my fingerprint. I hate the feeling of pushing the blade into my finger nail however, that's too easy to cause damage (to myself).

[Patrick Chase]

The hollow ground blade will be the easiest for this. Go through your regular routine of sharpening, then when you are completed, return back to the finish stone. Work the bevel and before you work the back check for a burr (it is very very light as this point). That should help to improve your thumb gauge for checking since you will know it is there with certainty. Work the back again and see if you can feel the burr.

If you're seeing light reflecting from the edge, then there is still some wear left. When its totally gone you can't see the edge at all.

I'll take some photos next time I sharpen and see if I can highlight the wear, it may be quite difficult to do with an iPhone but it is surprisingly capable on occasion.

IMO that falls squarely into the category of "asking the iPhone to do things it can't". For that matter it's probably out of the range of even a skilled photographer with professional-level macro equipment.

The sorts of burrs that are left by polishing stones are on the order of microns in size (see the first SEM shot here for example, which shows the aftermath of a Shapton 8K). The minimum focus distance on an iPhone corresponds to the equivalent of about 1:2 magnification on 35 mm or maybe a little closer. Even if the iPhone lens were perfect each pixel would correspond to ~15 um at the subject, and its lens is decidedly imperfect at minimum focus. The iPhone can't possibly image that burr. In theory you can get closer with close-up lenses like the Olloclips, but those are degrading (adding aberrations to) the image at the same time as they magnify it, so there's a fairly low limit to the amount of actual subject resolution you can gain that way.

I have one of these, a camera with 5.5 um pixels and a pile of macro lighting and support accessories, and even with that setup I don't think I could clearly image that sort of burr. In theory at 5:1 magnification each pixel would be 1.1 um at the subject, which might be just enough, but in reality diffraction spoils the party. The MP-E 65 is ~f/17 wide-open at 5:1 (5+1 = 6x bellows factor, 6*2.8 = ~17), and you realistically have to stop down to at least f/22 to maximize quality. At f/22 the Airy diffraction disc diameter is ~15 microns to the first null at the sensor, or the equivalent of ~3 um at the subject at 5:1 magnification. That's more (realistically much, much more) than 5X the resolution of the iPhone, but even so it's probably not enough.

Even optical microscopes would be challenged to image that sort of burr, again due to diffraction limits. That's why SEMs were invented in the first place after all.

[Brian Holcombe]

I was thinking more along the lines of picture showing light reflecting from a worn area that remains. For instance, yesterday evening I sharpened my chamfer plane, and while even with moving the block side to side it still wears the center of the blade significantly more than the other areas, I had worked up to the 10k stone only before seeing just a flicker still remaining in the center.....and returning to the 1k stone to remove it.

That sort of thing can sometimes be fairly difficult to find and remove. It could be mistaken as something other than what it is.

[Nicholas Lawrence]

Brian-
We've been through this in person before, and I still struggle to find the burr. I can easily raise, feel, and remove burrs at the very rough grits ( < 1000) when I am establishing the primary bevel. But as soon as I move up to the 1000 grit stone, and hone free hand, I can no longer feel a raised burr.

A lot of folks have made good comments about this. My finest stone is an 8000 grit Norton. I can usually feel the burr coming off of that stone. It is a lot less noticeable than the 1000 grit stone, but it is still there. Since I started using a strop, one thing I look for now is a very, very fine area of reflection near the blade edge. I usually strop the back first (one swipe), and will often see that little fine area of reflection when I look at the front of the bevel. A swipe on the bevel side, and it disappears. Another swipe on the back and it sometimes comes back. I suspect that is the wire edge or burr being bent back and forth, and after a couple of swipes on each side it disappears completely.

If you are having trouble feeling the burr, you may try looking for it that way (or I could be wrong about what I think I am seeing, in which case I am sure someone will correct me).

[Stewie Simpson]

A burr worked right up to my finest grit of honing stone. And no difficulties achieving a consistent and reliable cutting edge on my irons using traditional steel.

[David Sloan]

I have read and re-read all of your comments and would like to thank everyone. Obviously there is a lot of controversy about sharpening and I am greatly humbled by the expertise that is out there. When I am woodturning, I am sharpening all the time.
I need to have that same diligence (which has not been my practice up to now) when I am woodworking.