[OP]
Member
On a bevel-down plane, the unbeveled side of the blade hits the wood first does the shape of the bevel (concave, convex or flat) matter at all? It seems to me that any bevel shape, so long as the edge straight, there is adequate relief angle and the edge adequately supported, should be the same.... I know that in Japanese kanna a flat bevel is prized, I don't understand why Thanks -Howard
Member
I believe the flat bevel on Japanese planes is due to the laminated construction. A hollow grind would thin the hardened layer more than a flat grind and make it more likely to chip. At least that's the theory.
Contributor
That is an interesting idea. It would also hold for early western blades.Originally Posted by Greg Wease
It could also be that a flat bevel is based on tradition.
Traditions give way to new methods quicker in some societies compared to others.
Most of my blades have flat bevels for lack of a grinder.
When my plane blades show signs of a camber I know it is time to think about flattening my stones.
jtk
"A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
- Sir Winston Churchill (1874-1965)
Member
If the blade is to do any cutting, then the very edge must be hitting the wood first.
As long as the edge is sharp, and supported by enough metal so it won't chip, it wouldnt matter in the least what the rest of the bevel looked like, as long as it was a reasonable angle so it wouldnt flex. Id bet people can and will argue the virtues of the different shapes for days on end.
I like a hollow grind bevel with another single bevel at the tip. Sometimes i will find a chisel or plane with a rounded bevel. I cant sharpen them this way because they are difficult for me to get to a razor edge. I also question what the true cutting angle is on these,?
Member
"I cant sharpen them this way because they are difficult for me to get to a razor edge. "
An interesting contrast with
Paul Sellers - How to sharpen a handplane - YouTube
Best wishes,
Metod
Guest
I'd suspect the issue with not getting a razor edge has to do with starting with too steep of a primary bevel to begin with, and the convex edge effectively becomes a 40 degree angle or whatever.
There's a reason that most razors are in the 15-18 degree range.
No matter how sharp an edge is that is 40+ degrees, it is not going to have the effortless shaving sharp feeling that a 25 degree edge of the same polish has.
This discussion is going on several places at once, but there is no benefit to using a convex bevel on a plane if it decreases the clearance angle effectively (it just presents more bevel in the springback area of the wood to wear, and makes the plane feel dull earlier). It also doesn't reduce the time it takes to sharpen vs. any kind of powered sharpener and either a reference hone on a hollow or a microbevel hone on a flat ground edge.
None of that is to say you can't use a plane well with a convex bevel, but there is no successful argument that it is better than any other method on something that wears as fast and demands adequate clearance as a plane blade does.
It's the new popular thing because of a couple of videos now, though. The next time a set of videos is released by someone new, then there will be something else that is a fad in sharpening. In the last 5 years, it's been:
* guided hone and three bevel system with ruler trick
* sandpaper system with glass and exotic sandpapers
* hollow grind freehand
* freehand maintenance entirely with a second bevel put on freehand
* and now it's the rounded bevel, and some diamond film stuff (which will probably take off more as powder metals come on).
Anybody's guess about what's next? None of it makes a real difference if you're using your tools and they're giving you the surface you want (plane) or the feel and sharpness you want in the cut (chisel). I wish we had as many hand-tool only toolmaking posts as we do posts about sharpening.
Member
How about a flat primary bevel with hollow secondary bevel! Oh wait, that's already been done
Guest
I think we're due for a new and expensive machine that uses unidentifiable razorish potions as a slurry and has an adjustable camber attachment - maybe like a .05 micron diamond paste for the final step with camber in thousandths and a digital readout showing you what's going on.
Member
+1 to that, and also I'd like to see more handtool only projects posted in general.
Although admittedly, you, I, and others aren't exactly known for for our lack of participation in sharpening discussions.
Member
Careful what you wish for. CKTG is now selling a .1 (yes, that's one tenth of a micron) spray!
Guest
I've seen knife people talk about .05 micron, too. That was the smallest I could find when I wanted to make a spoof post on another forum.
I have people say, in earnest, that they were not satisfied with a thin bevel knife with a chromium oxide edge (like pure chromium oxide pigment, which is finer and more uniform than the ubiquitous green AO/CrO mix crayon), that they needed to go to that level to get a satisfactory working edge.
I wonder what they're cutting!! I shave off of chromium oxide pigment, and it is incredibly sharp to shave, and aggressive, and it is considered something that makes an edge more mild in the world of shaving (compared to diamonds).
I don't have any real problem with any sharpening medium and any sharpening method, they all work. I just get sort of a giggle when each new person/video comes out and touts their sharpening method and then people are looking to change what they do (this is not specifically in regard to the OP's question).
In fairness to paul sellers, at least in the trailer I saw, he basically says "this is the way I do it", and not "this is what i'm pushing and here's where you can buy all the stuff".
Contributor
Even with all of these and other "exotic" methods of edge achievement I think I will just stay with what has worked for me.In the last 5 years, it's been:
* guided hone and three bevel system with ruler trick
* sandpaper system with glass and exotic sandpapers
* hollow grind freehand
* freehand maintenance entirely with a second bevel put on freehand
* and now it's the rounded bevel, and some diamond film stuff (which will probably take off more as powder metals come on).
I once read something about people using a hollow grind because they didn't have the ability to do a flat grind without going convex.
It is possible to have a convex bevel and still have an edge that will cut. My guess is people who "rock" the blade while sharpening will have problems caused by the rounded bevel a few years down the road. Even if they don't, what reason can be given for me to change something that is working fine for me?
jtk
"A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
- Sir Winston Churchill (1874-1965)
Contributor
I'm waiting for a laser guided chisel so I can get it to go where I want. Sometimes my aim isn't too good.
Guest
I think that's a good idea.
I wouldn't go that far. I switched from flat to hollow grind because of speed.I once read something about people using a hollow grind because they didn't have the ability to do a flat grind without going convex.
They might have problems much sooner than that. Every edge on a bench plane that's been done totally by hand will have some level of convexity, but probably not enough to matter. Even a method that creates clearance problems from misuse will still work fine as long as the edge is sharp and there's any clearance at all. It just won't be as nice in use as an edge with more clearance. I think what you can decipher from very old irons that don't have a lot of wear is that the users liked to have plenty of relief. Whether that was to create a flatter bevel for hand honing, I don't know, they could've easily made a steeper bevel if they'd have wanted to.It is possible to have a convex bevel and still have an edge that will cut. My guess is people who "rock" the blade while sharpening will have problems caused by the rounded bevel a few years down the road.
This discussion is going on several places, and another forum user made the comment that we'll likely never see what the very good hand tool craftsmen did (the 18th century pre-automation types) because few planes have survived without molestation from late 19th century craftsmen, let alone what may have happened to them in the 1900s.
Member
Here's kind of a nice grit chart comparing, amongst others, Norton and Shapton grit size. It shows a 200,000 Shapton as 0.07 micron.
One can never have too many planes and chisels... or so I'm learning!!
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