Originally Posted by
Patrick Chase
All else being equal (cutting pressure etc) the durability of the edge is determined by its true geometry, not the cutting angle. The bevel is 31 deg in the example you give, period. We're not bending space-time here :-).
Of course all else isn't equal because as you say "everything gets stretched out", but that helps edge durability for two reasons. First, as you point out the cutting angle is reduced, which lowers total cutting force. In addition, that cutting force is spread out over 1/cos(14) = 1.03X as much edge, so even if the total cutting force were the same you would still see a 3% reduction in cutting pressure (as I said in another post, you need more like 30 deg of skew to realize significant benefits from this effect).
Per my last post, I'll stay away from debating physics. But I will say that your first sentence does not comport with my experience. A blade beveled at 30 in a common pitch plane will outlast the same blade bedded at 55 or 60, every time. I think this is a consensus opinion among people who have experience with a variety of BD angles (whereas it's not an issue for the BU folks, for obvious reasons).
Side comment: It strikes me that some of the other commenters in this thread are not speaking from experience. Making a skewed bench plane is tricky; making one that performs well under the high stress of shooting, particularly when one is using a low angle that leaves zero margin of error, is even trickier. I don't doubt that Phil Edwards can do it (I have very high regard for Phil), but he has many hundreds of planes under his belt. His success may not be relevant or helpful to less experienced, amateur planemakers.
A related issue is Derek's idea of rotation, rather than skew. I think it is a genius idea in theory, but if there is one thing trickier than skewing, it's rotation. Anybody here ever built such a plane (for example, a badger plane, which is both rotated and skewed)? It's a lot harder than it looks! I would not recommend it unless you've already built a lot of more conventional planes.
"For me, chairs and chairmaking are a means to an end. My real goal is to spend my days in a quiet, dustless shop doing hand work on an object that is beautiful, useful and fun to make." --Peter Galbert