Back bevel works well (and two questions)

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I own the LV low angle smoother and have an extra blade, the high angle optional blade, ground at the factory to 35 degrees. I've known for some time that putting a back bevel on it is supposed to reduce tear out but being the procrastinator that I am, I hadn't ground the back bevel until this afternoon. I put an 8 degree (give or take) bevel, 1 mm wide on the back and gave it a work out on an oak drawer front that I'd set aside early this year because I couldn't tame the tear out without sanding it forever.
Early this year: A couple runs through the planer resulted in tear out no matter how light a cut or which direction. By the time I'd run it through a few times, I decided it was too thin to be installed along side the other drawers and ended up cutting a new front. If I'd owned a thickness sander, I would have put it through that in the first place, but being in a hurry to remove old stain, I ran a bunch of drawer fronts through the planer after scraping off the lacquer finish. The rest came out flawless.
I found that problematic drawer front today and gave it a go with the modified plane blade. It was like a miracle! Almost like using a scraper plane, but faster. The surface was left silky and all the divots disappeared after a half dozen strokes. Very cool.
Oh, and kudos for Robin and company designing the new honing guide. It paid for itself today.
And I know nearly every one of you here already knows about back beveling a blade. I just wanted to share...
Question: Wouldn't a back bevel on planer blades make them chip and wear out much faster?
Is there a 12 step program for procrastinators?
Dave
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David wrote:

back. That's the procrastinator. Just reverse that for the solution.
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I cannot argue with your good results. What I don't understand is why this worked as well as it did. As I understand it, you added a bevel on the opposite side of the normal bevel. This is the definition of a back bevel for standard bevel-down configuration. It increases the cutting angle. However, on a bevel-up plane such as the LV low angle smoother, it has no affect on the cutting angle. To increase the angle, you would shift the angle from the factory ground 35 degree angle to something like 40 degrees or add a 5 degree microbevel.
Did I misunderstand something?
Bob
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Chip form.
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I don't have any idea what your two word reply means. Would you like to expand that answer?
Bob
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The back bevel also causes the shaving to curl faster, breaking it over a relatively shorter radius, depriving it of long fiber strength to tear out.
http://www.leevalley.com/images/item/Instructions/05p2301e.jpg
Shows the exaggerated view.
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Thanks for posting the link. This picture illustates exactly the point I've been trying to make. That's a picture of a bevel down (conventional) plane. The Lee Valley Low angle smoother described by the OP is a bevel up plane, like a block plane. Back bevel does not affect cutting angle on a bevel up plane, so I don't understand why he got better results unless his plane just wasn't sharp to begin with.
Bob
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It affects clearance angle, which can increase the sharpness angle while making the edge more durable. See Hoadly on sharpness.
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George wrote:

ground off the bevel and put a TINY back bevel that was maybe 1/4 to 1/3 of a MM. It wouldn't even cut. I had the blade sticking way out from the sole of the plane and got no cutting action. I guess I got lucky the first time I put a back bevel on (1 MM wide). The blade was sharp before I did that, and I'm not really sure if I had tried it early this year on that tear out prone drawer front. Maybe it would have worked ok with no back bevel, but I must say it worked very well with a 1 MM bevel, but was useless with a tiny BB. I do realize that BB are primarily for bevel down planes.
Dave
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I'm pretty convinced that you simply produced a better sharpening job, rather than making any shift in the planing geometry. That's why it worked.
I was a little surprised you mentioned you had trouble with tear out on the oak to begin with. I've not had much trouble with oak and the smoothers I own. I did not do anything special to them except sharpen them. Now when they were not so sharp, I had all kinds of trouble with tear out.
Bob
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BillyBob wrote:

oak that tears out a lot, but this ONE piece has got a couple square inches area that's a bear to plane cleanly. I got it perfectly smooth, then grabbed low angle block plane and in one pass left it looking ragged again. That area, when smooth, looks to my eye like the rest of the surface. Is there no way to tell what wood will tear out, by some visible feature, in the grain?
Dave
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I don't have a weatlh of experience, but I know when the grain looks like little eddys in a pool of water its going to be a bear. With a very sharp blade, you are able to make other adjustments that help tear out. First, set the cut depth to make very thin shavings. If the plane has a mouth adjustment, set it very tight. Lastly, planing diagonally or in kind of a swirling motion may help with these tough areas. Alternatively, a cabinet scraper may save the day.
Bob
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BillyBob wrote:

to hold it just right to see daylight through the tiny slit. :) I have a LV scraper plane which I've learned to adjust pretty well now, so that I can get a wonderfully smooth surface. Thanks for the additional suggestion (swirling), Bob.
Dave
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What is clearance angle? Who or what is Hoadly?
Bob
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How does it make the edge more durable? It seems to me that it makes the cutting edge thinner, which results in an edge that will dull quicker. Since its a bevel up plane, the angle of cut remains the same and the back bevel just removes more metal behind the cutting edge.
Bob
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Au contraire.

No: / / / / | Exaggerated back bevel on bevel up plane | / | / | / |________/
/ / / / | No back bevel on bevel up plane | / | / | / |/
--
Dr. Juergen Hannappel http://lisa2.physik.uni-bonn.de/~hannappe
mailto: snipped-for-privacy@physik.uni-bonn.de Phone: +49 228 73 2447 FAX ... 7869
  Click to see the full signature.
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I am always willing to admit I am wrong. You are right, I was wrong. Thank you for posting the pictures, that helps. I've learned something Back bevel does indeed make the edge more durable. I had it confused with micro bevel.
Bob
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On Tue, 04 Oct 2005 17:02:06 GMT, "BillyBob"

back beveling a bevel up plane makes the edge thicker.
that is if you define the back as the side of the blade without a bevel. if you define the back as the side away from the wood, then a *front* bevel would make the edge thicker.
regardless of that bit of obfuscation, any secondary bevel, front back or inside out will make the edge thicker. that's all fine and good until the angle of the bevel against the wood exceeds the angle of attack- or as someone else moer clearly just called it, the clearance angle. when that happens the plane ceases to cut.
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snipped-for-privacy@all.costs wrote:

I read your statement. I agree. seems counter-intuitive, doesn't it??
Dave
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You are correct. I confused back bevel with micro bevel. I need to take my own advise often given out. When in doubt draw pictures or make a model to really understand.
Thanks, Bob
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