Hand Tools

Subject:
A test with bevel up planes, buffing, and tearout *PIC*
Response To:
Unicorn and Bevel Up ()

Winston
I did some experimentation with tearout control with buffed blades. My experience seems to be very similar to David's.

Overall, I'd say that the pushing resistance isn't noticeably increased by the tiny bevel added by buffing the blade. But the tearout resistance is better. And of course sharpening a bevel-up plane this way is very quick and easy, and you don't have to be as careful about clearance angles as you do with bevel-down planes.

Regarding pushing resistance, it wasn't noticeably increased for me, though I supposeiIt's possible that someone with a better-calibrated arm might notice something.

I don't have any exotic woods laying around and I don't really use them. I did find some black walnut that had a section of reversing grain. This is what it looks like from the side.

For testing, I used my Veritas low-angle jack (bevel-up) with a 12-degree bed, and a #5 (bevel down) with the standard 45-degree bed. In the Veritas, I used some blades buffed, and some not. For the buffed blades, they sharpened on a Shapton 1000, then Sigma Power 6000 (working the bevel and the back), then buffed with 1 micron green compound. For the non-buffed (flat-honed) blades, I used the 1000 and 6000 stones, then a Shapton Pro 12000.

I tried to take a reasonably fine shaving, like .0015"-.002". With the bevel-up plane, I closed the mouth so it was pretty tight.

Below are pictures of the piece of wood after planing with various setups.

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Bevel-up 25 degree (on 12 degree bed), buffed. There was a bit of tearout.

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Bevel-up 32 degree (on 12 degree bed), not buffed. This had a 44 degree cutting angle, very close to that of a bevel-down bench plane.

There was tearout with the cut I was taking (around .0015"-.002")

After that, I tried taking a very light cut. There was no tearout in this case:

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Bevel-up 32 degree (on 12 degree bed), buffed. The resistance to pushing didn't feel noticeably greater than the flat 32-degree blade.

There was no tearout.

I also tried taking a very heavy cut and got tearout. This was a much deeper cut than I would use in the smooth-planing, and it was deeper than what I tried with any other plane/blade combination in this series of tests, but I wanted to if I could get tearout with this setup, and the answer is yes. I think the depth of the tearout was limited by the tight mouth, though.

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Bevel-up 45 degree (on 12 degree bed), flat. This had a 57 degree cutting angle. Noticably more resistance to pushing than the previous ones.

There was no tearout. However, the surface quality wasn't quite as good as with the lower angles. It's pretty subtle, but in the pictures, you may be able to see that the surface is slightly more matte -- there's less contrast between the dark and light areas. I think this is because the blade had more of a scraping action here. Again, the difference in surface quality is subtle.

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For comparison, I also used the #5 (bevel-down) plane. For these tests, the blade was buffed on the bevel side.

Bevel-down (45 degrees) with the chipbreaker set far back (around 1.5mm).

As expected, this setting had tearout. The cutting angle is 45 degrees, which is close to the bevel-up plane with a flat-honed 32-degree blade -- that one had a 44 degree cutting angle, and of course, no chipbreaker. In terms of tearout resistance, this plane's chipbreaker was too far back to help at all.

The tearout in this case was slightly worse compared to the flat-honed 32-degree bevel-up condition, and I think it's probably because this plane has a wider-open mouth. (I closed up the mouth in the bevel-up plane, but didn't bother to for this bevel-down plane, because it's a bit of a pain to do so.)

I tried taking a much lighter cut, and managed to avoid tearout:

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Bevel-down (45 degrees) with the chipbreaker set very close. This had the most resistance to pushing. No tearout.

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For bevel-up planes, buffing the blade seems like a clear winner: It makes it easier to get a perfectly uniformly sharpened blade, reduces tearout at any given bevel angle, but doesn't significantly increase pushing resistance. It also increases edge durability, as I found when I tested buffed blades in a plane used for shooting.

I don't think this will make bevel-up planes able to completely replace bevel-down planes with respect to tearout control, but I think it can make them more versatile.

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I should also mention that although unicorned edges are more durable, they are not indestructible. I was using the 25 degree buffed blade for some actual work, and planed through a very tight knot in cedar. It caused visible damage to the edge (which in turn left visible tracks). You can seee that the center of the blade doesn't reflect the same way as the rest of the blade.

Here's the damage viewed through the microscope:

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