Bevel angle on traditional bench planes: why should it matter?

[Marc Hills]

As the new generation of bevel-up bench planes teaches us, it's the effective cutting angle, not the bedding angle, that matters when the blade is oriented bevel side up.

A bevel-down plane, on the other hand, is strictly limited by the bedding angle of the frog. The blade on a 45 deg smoother will always present at 45 deg relative to the wood, regardless of how it is beveled.

That being said, why is the common wisdom that a traditional plane iron should generally be beveled at 25-30 degrees? Why not 35-40 degrees? Wouldn't that make the cutting edge a bit more durable? So long as you bevel it a bit less than the 45 degree bedding angle to ensure relief, why would you want the bevel any sharper?

I used to think that a sharper bevel would make the blade cut better, but with these new bevel up smoothers and the steeply-pitched bevels, I'm beginning to wonder. I mean their function establishes the principle that it's the angle at which the leading edge meets the wood that matters, right?

Another way to look at it is: what does the wood care what is going on behind the leading edge of the blade? Besides reduced edge durability, what is a 30 deg bevel giving you that you can't get with a 35 deg bevel on a bevel down bench plane?

I'm sure I'm missing something here, just as I'm sure I'm thinking about this way too hard. Can anyone help me out?

[Dan Moening]

The blade on a 45 deg smoother will always present at 45 deg relative to the wood, regardless of how it is beveled.

Well, this is true assuming the traditional way of beveling.

What if you were to put a 10° back bevel on a bevel down plane?

This would give you an effective cutting angle of 50°.

In answer to your question {and its antedoctal as I don't own a LV, or LN LA bevel up plane...yet}:

On these new breed of BU planes the blade is supported all the way to the edge. Whereas the traditional bevel down blade is supported to the start of the bevel.

Minor differences to be sure, but significantly measurable.

Still a newbie myself, so I'm always interested in what others experiences are...though tend to try things on my own more often than not.

It isn't until something fails that I consider fixing it. If my results aren't what I want then I'm more apt to change.

[Peter Mc Mahon]

Hi Marc. You are correct that it is the angle presented to the wood that makes the difference. Bevel down planes with a 45* angle bed do present a 45* angle to the wood. You can however back bevel a blade at say 10* and present a 55* bevel to the wood. Your other question about why not bevel at 35-40* is a good one. I suppose that the edge would be a little bit stronger but honing would be slightly more difficult. I sharpen sort of like the way that David Charlesworth sharpens. The iron is ground on a bench grider at 22* or so, the secondary bevel is honed at 25* or so, and the microbevel is honed at 28* or so. Since the edge is at a more acute angle it presents less steel and will hone quicker. Hope this answers your question. Peter

[Joel Moskowitz]

just for jollies take a BD plane - grind/hone a 30 bevel on the iron and try it. Then grind/hone a 25 degree bevel on it and try it. guess what the 25 degree bevel works better. I have no idea why - actually I have some idea, but i can't really articulate it but just try it. you don't have to agree or disagree with me -it's an easy enough test. I tried it and I am convinced.

as for BU planes supporting the iron more than BD planes - not really true. the BU plane iron is supported from the edge of the bed (which isn't a knife edge and is unsupported at a very thin section from there to the cutting edge. the force of the cut can bend the thin tip of the blade against the edge. the BD plane the blade itself isn't supported past the bevel but the force of the cut goes into the body of the blade giving it a lot of support. While I haven't dont any testing I would bet that a BU plane with a higher effective angle (EA) supports thicker shavings than a BU plane at lower EA and a BD plane supports thicker shavings than a BU plane. it's actually a theory worth testing because it may explain why BD planes were more popular when people did more milling of wood by hand than today when most plane testing and plane use is on very very thin shavings.

[Ben Knebel]

just for jollies take a BD plane - grind/hone a 30 bevel on the iron and try it. Then grind/hone a 25 degree bevel on it and try it. guess what the 25 degree bevel works better. I have no idea why - actually I have some idea, but i can't really articulate it but just try it. you don't have to agree or disagree with me -it's an easy enough test. I tried it and I am convinced.

as for BU planes supporting the iron more than BD planes - not really true. the BU plane iron is supported from the edge of the bed (which isn't a knife edge and is unsupported at a very thin section from there to the cutting edge. the force of the cut can bend the thin tip of the blade against the edge. the BD plane the blade itself isn't supported past the bevel but the force of the cut goes into the body of the blade giving it a lot of support. While I haven't dont any testing I would bet that a BU plane with a higher effective angle (EA) supports thicker shavings than a BU plane at lower EA and a BD plane supports thicker shavings than a BU plane. it's actually a theory worth testing because it may explain why BD planes were more popular when people did more milling of wood by hand than today when most plane testing and plane use is on very very thin shavings.

You raise a good point Joel --a point I also tried to make over on Woodcentral--that the BU plane iron edge risks being bent over and with heavy use I think we'll see that happen more often than people would like.

One other point---a lot of folks seem to think BU planes are something new--they're not--they've been around for hundreds of years--in mitre planes, block planes, chariot planes, all of which were not as heavily used as the BD bench planes. There were even BU smoothers--mostly in Europe-- but they didn't grab hold and although I don't have scientific evidence I think edge curling is one reason why they went out of favour for heavy everyday use.

We may not always know why but there is a reason that the oldtimers did what they did--over hundreds and hundreds of years of experience and use they determined that the BD plane was best for bench planes.
And before people get on the--"just because it was always done that way doesn't mean it is the right way bandwagon" let me say that; while that might be true for a lot of endeavours I don't beleive it to be as true for fields of work that have been around for hundreds and thousands of years as woodworking has. A case in point--If you follow medicine at all you know that our modern researchers are discovering that a lot of the the " old wives tales" remedies that have been ridiculed for years actually work--with far less side effects than some of our medicines today that proport to cure similar ailments. Why--even leeches have made a resurgence in medicine as have maggots for handling badly infected wounds. The same is true for woodworking.

A saw works as a saw always has; a hammer works the way a hammer always has, a chisel works the way a chisel always has and planes work the way they always have.

Our modern propensity for changing things for changes sake and for thinking that we can improve anything and everything has become a diservice to the hand woodworking world--I haven't yet seen a modern hand tool that outperforms tools made 150 years ago. Edges may last a little longer with some of the modern steels but that's about it. Indeed most modern hand tool manufacturers struggle to create tools that work as well as those of 150 years ago and most actually emulate the old designs--why--because they worked.

If you research long and hard enough you'll find old design elments in ALL of the modern hand tool products. We tend to be very ignorant of our own histories and this is particularly true of our industrial and technological histories. As a consequence it is very easy for people to introduce a product and call it "new" and we go " Oh how neat and innovative" when all they've done is copy something that has been done before.

My 2 pennies
Best Regards
Ben

[Steve Wargo]

Joel & Ben,

Thank you.

[Gene Collison]

You raise a good point Joel --a point I also tried to make over on Woodcentral--that the BU plane iron edge risks being bent over and with heavy use I think we'll see that happen more often than people would like.

One other point---a lot of folks seem to think BU planes are something new--they're not--they've been around for hundreds of years--in mitre planes, block planes, chariot planes, all of which were not as heavily used as the BD bench planes. There were even BU smoothers--mostly in Europe-- but they didn't grab hold and although I don't have scientific evidence I think edge curling is one reason why they went out of favour for heavy everyday use.

We may not always know why but there is a reason that the oldtimers did what they did--over hundreds and hundreds of years of experience and use they determined that the BD plane was best for bench planes.
And before people get on the--"just because it was always done that way doesn't mean it is the right way bandwagon" let me say that; while that might be true for a lot of endeavours I don't beleive it to be as true for fields of work that have been around for hundreds and thousands of years as woodworking has. A case in point--If you follow medicine at all you know that our modern researchers are discovering that a lot of the the " old wives tales" remedies that have been ridiculed for years actually work--with far less side effects than some of our medicines today that proport to cure similar ailments. Why--even leeches have made a resurgence in medicine as have maggots for handling badly infected wounds. The same is true for woodworking.

A saw works as a saw always has; a hammer works the way a hammer always has, a chisel works the way a chisel always has and planes work the way they always have.

Our modern propensity for changing things for changes sake and for thinking that we can improve anything and everything has become a diservice to the hand woodworking world--I haven't yet seen a modern hand tool that outperforms tools made 150 years ago. Edges may last a little longer with some of the modern steels but that's about it. Indeed most modern hand tool manufacturers struggle to create tools that work as well as those of 150 years ago and most actually emulate the old designs--why--because they worked.

If you research long and hard enough you'll find old design elments in ALL of the modern hand tool products. We tend to be very ignorant of our own histories and this is particularly true of our industrial and technological histories. As a consequence it is very easy for people to introduce a product and call it "new" and we go " Oh how neat and innovative" when all they've done is copy something that has been done before.

My 2 pennies
Best Regards
Ben

Ben,

I'm not disagreeing with anything you said, I have numerous planes both bevel up and down, assorted bedding angles. it is interesting to note that two of them in particular, a BU jack and BU smoother are notably good performing planes. I hone the irons on both of these to 38 degrees to give a working angle of 50. On one of my recent projects I put a lot of miles on the BU smoother. Thinking it had to be time to sharpen, I pulled the iron and looked at it under 10X magnification. the edge was still sharp, I was unable to see the edge after wiping it with a strop. No deformities whatsoever. The wood I was working was white oak. These planes surprise me in two ways, the length of time that they stay sharp and they way the perform with the 38 degree angle which is getting somewhat oblique. But I also think the oblique edge is adding a lot to the longevity of the edge. IMO bevel up smoothers seem to be a pretty darn good planes. i'm not stating a case for BU vs. BD, just relating my observations. Opinions?
Joel, I have sharpened at both 25 and 30 degrees. i'm not doubting that what you say is true but I can't say as I see much difference. But then again I haven't done a side by side comparison which may prove interesting, I will have to try it. History has probably got it right.
It's interesting to note that Terry Gordon of HNT Gordon says that you can't achieve true sharpness at over a 30 degree bevel. I'm not sure about that one either, the BU blade at 38 works really well. Contrary to that, Lee Valley I believe recommends 35 degrees as a finished angle in their BD planes. Certainly they wouldn't do anything detrimental to the performance of their product. I sharpen BD planes at 28, sort of middle of the road for edge retention and sharpness. It seems to work well.

Gene

[Jerry Palmer]

Theoretically you can get a sharper edge on a more acutely angled bevel. The ~30 degree bevel angle generally recommended for BD planes is a compromise between the theoretical sharpness obtainable and the strength of the edge.

There is also a limit to the height of the bevel with BD planes. You need a certain amount of clearence behind the edge and taken to an extreme, the bevel itself will prevent the edge from contacting the wood you're trying to cut.

[Derek Cohen]

A couple of points to consider, in response to questions posed above:

1. Joel, a 25 degree bevel will be "sharper" than a 45 degree bevel (assuming both honed equally on the same media) in that it has greater "penetration".

The question that I ask (and am presently investigating) is "which lasts longer - the bevel down plane with an effective cutting angle of 60 degrees, or the bevel up plane with the effective cutiing angle of 60 degrees"? This assumes that the BD plane has a frog angle of 60 degrees and a bevel of either/both 25 and 30 degrees. Verses the BU plane with a bed of 12 degrees and a bevel of 48 degrees.

2. Ben, yes BU planes have been around a long time - of notable mention consider the Stanley #62 and #164. What has not been around for all these years, however, and only available in very recent times, is the material to build durable and lasting planes. Such as ductile iron. The success of the LV and LN planes owes a great deal to this material. The design of BU planes involves greater stresses around the bed/mouth area than BD planes. The afore mentioned Stanley planes (of which I own a #62) have a reputation for chipped mouths.

Regards from Perth

Derek

[Pam Niedermayer]

An edge is a line of points defined by two surfaces meeting. The sharpness of this edge is not affected by the angle at which the two surfaces meet.

Pam

[Derek Cohen]

An edge is a line of points defined by two surfaces meeting. The sharpness of this edge is not affected by the angle at which the two surfaces meet.Pam

Pam, note that I linked "penetration" to bevel angles.

Compare two paring chisels, one with a 20 degree beveled edge and the other with a 30 degree bevelled edge (same blade width, same sharpening process). No contest which will cut more easily.

Regards from Perth

Derek

[Gene Collison]

Pam, note that I linked "penetration" to bevel angles.

Compare two paring chisels, one with a 20 degree beveled edge and the other with a 30 degree bevelled edge (same blade width, same sharpening process). No contest which will cut more easily.

Regards from Perth

Derek

Derek,

I understand your example of sharpness when related to paring chisels, even LA smooth planes. But when you flip the blade, it's a different ballgame. I don't understand how it relates to BD smooth planes as stated by the poster. As long as there is sufficient clearance behind the edge to allow planing the desired thickness shaving, I don't see how it makes much difference whether the angle is 25 or 35. Case in point, taking a typical .001 shaving using a BD smooth, not very much clearance is required at all. And if you link penetration, it doesn't take much to get .001 penetration in wood even if you should start in the middle of the board. If you start off the board, penetration isn't even a prerequisite.

I think Pam is right too with qualifications. Negative rake tooling is commonly used on metal turning lathes with carbide insert tooling where the cutting edge sits at a negative angle to the workpiece. Depending on the type of insert, the cutting edge is ground at a 90 degree bevel where the edge is actually cutting. This type tooling cuts just as well at the 90 degree bevel as any other angle that could be ground on the tool. Basically because even though it is ground at 90 degrees the 90 degree edge is still as close to zero radius as possible, thus still very sharp. I think what Pam is suggesting in her post is that when two planes come together and the resulting edge is as close to a zero radius as possible, it doesn't matter what the angles are. Pam, you can jump all over me if I misinterpreted your thinking.

Gene

[Pam Niedermayer]

Yes, Gene, that's pretty much what I meant. I also like your negative rake example, seems to explain why floats and scrapers are so effective.

Pam

[Mike Wenzloff]

Snip...

Negative rake tooling is commonly used on metal turning lathes with carbide insert tooling where the cutting edge sits at a negative angle to the workpiece. Depending on the type of insert, the cutting edge is ground at a 90 degree bevel where the edge is actually cutting. This type tooling cuts just as well at the 90 degree bevel as any other angle that could be ground on the tool. Basically because even though it is ground at 90 degrees the 90 degree edge is still as close to zero radius as possible, thus still very sharp. I think what Pam is suggesting in her post is that when two planes come together and the resulting edge is as close to a zero radius as possible, it doesn't matter what the angles are. Pam, you can jump all over me if I misinterpreted your thinking.
Gene

Hi Gene,

Negative rake tooling for metal work exists when the finished surface must be as smooth as possible.

Postitive cutters create fine chatter lines on the surface of many metals and so are not used in those situations.

A woodworking example would be a scraper without a hook, which works best when held in a device that controls depth--think Stanley #12 / #112. Too much negative rake and the wood compresses at the cutter and the reult, if any, is minimal.

Decrease the negative angle and fibers begin being torn from the surface. 0 (zero) rake and longer fibers begin to be produced. Soon into the postive rake and increaseingly longer fibers are removed until eventually the angle will begin to shear consistently and a shaving is produced.

MikeW

[Mike Wenzloff]

Pam,
I would be interested to see a float with negative rake. 0 (zero) and greater rake is all I am familiar with. I would tend to think a float with a negative rake would merely slide along the surface.

Thank you, Mike