Back Bevels on Japanese Planes?

[Acharya Kumarswami]

I recently ran across Derek Cohen's piece (I believe Derek is a SMC member, too) about the need for back bevels on plane irons and was convinced that this is a good practice, contrary to my previous convictions. I've gone over to using micro bevels front and back on Western plane irons, but I wonder about trying front bevels on Japanese irons, of which I have quite a few. One might argue that microbevels on the front are unnecessary, since one is only working with a small strip of hard steel, the bulk of thickness being cast iron, unlike the Western blades that are all hard steel.
But does anyone use back bevels on kannas? Certainly there is the inherent problem of the land being rather small because of the hollow. Just curious if anyone has gone through all this. Also, one needs to face the issue of tapping-out with the Japanese kannas, which I have yet to get into fully. It is related, because if the blade is tapped out sufficiently, the land will be large enough for a back bevel.

[Frank Drew]

None of the Japanese carpenters with whom I worked put any kind of secondary bevel, either front or back, on their plane blades or chisels, and I haven't since heard or read of it being done. As you note, a back bevel might be particularly problematic due to the hollowed back on these tools.

I'd be interested to learn if someone has done this with Japanese edge tools and has had improved performance.

[Terry Beadle]

Back bevels on a kanna can be done but it's against Japanese woodworking philosophy and costs. A kanna blade is the most expensive part of it. The Japanese mentor would probably tell you to sharpen the blade properly if the tear out was significant or recommend you make a new dai for it at a higher angle. If you put a back bevel on a kanna blade you are shortening it's working life and putting it at risk more than it should be. Frankly, the kanna I use cut through the toughest grain I deal with no problem. Especially the 47.5 degree kanna.

Back on costs, a Stanley replacement blade is $17. A decent quality kanna blade is 5 to 8 times that much and if you back bevel to the blade cavity, you have to tap it out and that risks the blade to crack. Tapping out is a careful task and not with out risk.

I would spend much more time getting my card scraper's sharp and functioning than risk a kanna smoother blade. I would put a back bevel on a woodie or classic Stanley long before risking a kanna blade. It must be my Scottish genitics ( hoot! ). I would also say that a properly sharpened kanna blade adjusted to take 1/2 thou shavings or less will deal with any grain or hardwood characteristics with out a back bevel needed. The kanna with the 60 degree bed from Japan Woodworker will perform a polishing plane function in cocobolo or ebony as is but if you needed a back bevel for a particularly difficult situation, I think it would be a lot less risk to put a back bevel on it than an expensive traditional kanna blade. Derek Cohen can speak more properly to tough grain situations and what blades to use.

Just my 2 cents.

Enjoy the shavings !

[David Weaver]

I've done it, in two cases, and I wouldn't do the secondary bevel on the bevel side for any reason other than the one I'm about to say.

On my yamamoto special cutting steel plane, i will put a shallow secondary bevel on the edge because I use it for rougher work than smoothing (and on hardwoods), and it is much quicker to do that. The angle on the plane is 47 1/2, which allows for that. The final bevel is at about 30 or 32 degrees, with the primary bevel around 27. it works very well, and the edge lasts a little longer than it does around 26 or 27 degrees, probably due to the roughness of work, and maybe due to the alloy.

I have "ruler tricked" (with a 0.5mm feeler) some cheaper irons just for speed and ease. I have not added any back bevel of significance, just a degree or so. The performance of the iron is identical to properly sharpening. It shouldn't be necessary with proper maintenance of the ura, but the two planes I do it on were irons that were not properly flattened by the manufacturer ( they were cheap) and the flats are large. The edge is easily as good as it is on a properly maintained iron, and the attention to the back is quick and minimal.

Odate mentions in his book that carpenters might back bevel (not microbevel on the bevel side) the edge of a new plane or do it on a plane that is being used for especially abrasive wood - to strengthen the edge to avoid chipping in the former, and in the latter, I guess the same reason (i can't remember if he discussed the second benefit being a steeper angle on difficult wood). He pretty much forbids microbeveling and hollow grinding of any type, but I do it (add a secondary bevel) without reservation on a steeper pitch plane on the condition that the primary is the same as it would be without microbeveling, etc.

There should be no reason to do the ruler trick on a properly maintained iron with the ura set up so that the hard steel is just a narrow strip. It won't necessarily hurt if you do it, but once you do it, you'll be doing it every time. I would never use anything but the final polishing stone to do it (which should be the case for the ruler trick in general). I do think a beginning sharpener will get a better edge with it, but only because it forces you to run the polishing stone all the way to the edge. Still, I'd try it for a bit on a cheap plane first before deciding you want to do it on a nicer iron.

I really like the ruler trick a lot for western irons. It allows you to get a good hone to the bleeding edge of very tough irons that would otherwise take more time to lap off the wear properly.

[David Weaver]

If you guys want to experiment a little, the funjii plane from JWW works fine. The iron is fairly thick, the plane is cheap, it doesn't hold an edge exceptionally long, but probably similar to a high quality western high carbon steel iron, and it's probably the same hardness. It can be had in 65 mm, so it feels like a "big boy" plane, and not a block plane.

It's nice to have a couple of them around to beat on (for $60 or $70) before you go hamming around on a nice iron, and you can still use them for productive work down the road. (they are some sort of white steel or maybe yellow so they take a very good edge). They will take shavings as thin as the limits of your sharpening (easily less than half a thousandth), they just don't have the edge holding of a properly made white steel plane and the dai is not nice like a high dollar dai. You could either leave one with a high effective angle, or camber the iron and use it for rough boards (that's what I do, and I sharpen it with a belt grinder and a leather strop belt or a leather strop on a disc sander wheel - shokunin would turn in their grave if they saw that going on, but I am controlled by nothing other than my laziness, so fast and good results it is).

I don't, however, think that a shallow back bevel for the purpose of sharpness and honing ease will expedite the need for uradashi. If it is steel, then probably so, but even at that, a fair amount of metal removal (perhaps half a mm or less) only happens the first time you do it, after that, the bevel is moving back no faster than it would with regular honing if you use a light touch and just remove the visible wear on the back bevel each time.

But that kind of experimentation is great for the funjii level of planes. Just my opinion.

[Pam Niedermayer]

No back bevels, microbevels, or hollow grinds on any of my Japanese edges. Period.

Pam

[David Weaver]

No back bevels, microbevels, or hollow grinds on any of my Japanese edges. Period.

Pam

Pam...you're such a stick in the mud!!! :)

[Dale Osowski]

No back bevels for me, no sub blades either ;-)

[David Weaver]

No sub blades for me, either.

[Pam Niedermayer]

Pam...you're such a stick in the mud!!! :)

Booyah!

Sub blades for me? Seldom.

Pam

[Johnny Kleso]

I dont have any Japanese planes but see no reason to add a back bevel.
The backs are hollowed out unlike western blades and should be cake to sharpen compared to westen blades IMHO

[Stuart Tierney]

Acharya,

Please don't. One of the main reasons all the effort went into making the back hollow, the blade laminated and mostly soft iron is to make them easy to sharpen, basically a built-in back bevel and front microbevel.

You can go right ahead if you wish, but of all the things to try with a kanna, it's one I won't try myself. And believe me, I've done some seriously odd things to kanna...


Possibly the only reason that's really worth it is the temporarily increase the blade's angle of attack to the work. Once the job is done, tap out and make it all flat again either straight away or over the time it takes to slowly work it out.


But it's your tool, and you can do whatever you want to it. We can tell you "no, no!", but it's still your tool.

Stu.

[Stanley Covington]

Blasphemy!

[George Beck]

It would seem to me that this entire back bevel, micro bevel and hollow grind business runs contrary to the design of a japanese blade. The main purpose of these methods, it seems to me, is to save time not polishing steel which will never see wood. This is taken into account in the nature of japanese blades.

I don't use hollow grinding, micro bevels or back bevels.

[Derek Cohen]

I recently ran across Derek Cohen's piece (I believe Derek is a SMC member, too) about the need for back bevels on plane irons and was convinced that this is a good practice, contrary to my previous convictions. I've gone over to using micro bevels front and back on Western plane irons, but I wonder about trying front bevels on Japanese irons, of which I have quite a few. One might argue that microbevels on the front are unnecessary, since one is only working with a small strip of hard steel, the bulk of thickness being cast iron, unlike the Western blades that are all hard steel.
But does anyone use back bevels on kannas? Certainly there is the inherent problem of the land being rather small because of the hollow. Just curious if anyone has gone through all this. Also, one needs to face the issue of tapping-out with the Japanese kannas, which I have yet to get into fully. It is related, because if the blade is tapped out sufficiently, the land will be large enough for a back bevel.

Hi Acharya

What article are you referring to?

I rarely advocate the Ruler Trick, with the exception of BU smoothers. I
also do not have any Japanese planes (I do have Western woodies that
resemble Japanese planes, however).

I do not use secondary bevels, with the exception of BU plane blades, where
they are necessary to create high angles. For all the rest I hollow grind
and freehand on the hollow. That does create a microbevel, but one that is
coplanar.

I would never use the Ruler Trick or a secondary bevel on a Japanese blade -
the thin hard tool steel layer would be threatened. I do use a 10" Tormek to
create a hollow grind, but this hollow is very shallow.

Hope this helps.

Kind regards

Derek

[David Weaver]

I don't understand why the edge would be threatened (actually, i'm playing coy a little saying that, because I know the edge wouldn't be threatened were it done properly).

I think if most people who used japanese irons would microbevel a degree or two on top of the primary bevel when they use their final stone, they would have a better edge. It would remove the need for the skill and time it takes to work the primary on a very fine finishing stone.

Let's say the primary bevel is at 27 degrees. a 2 degree microbevel wouldn't really affect clearance on a plane that is effectively bedded at 40 degrees or so (8/10 bu plus the taper of the iron, which is probably a couple of degrees).

That would leave a clearance angle in the 10-12 degree range. While there's some recent dispute if this is burnishing the work, there isn't much dispute that a plane cuts very well with that angle, especially on face grain and long grain.

AT the same time, the ruler trick wouldn't really threaten the back because it should not be taken to a level of any appreciable depth, just done at the very edge to get the scratches on the finest stones to be aligned with the cut.

If a back bevel is added to deal with difficult wood, it should only a couple of swipes of a polish stone - a very small one, and it will effectively work the same as one much larger.

These are not the same kinds of principles added to a western iron where the secondary bevel (on the bevel side) might be much steeper, but I do think for beginners who may not be used to the amount of time that it takes to properly run up a very hard japanese iron, they could be a way to see improved results without spending several times as long on their japanese irons vs. what they would with a hollow ground bevel down western iron freehand.

The more we talk about this, the more I'm inclined to do it. The only reason I see not to is if you are using expensive finishing stones, you run the risk of grit contamination if you need to use a honing guide to do this.

[Acharya Kumarswami]

Hi, Derek

thank you for responding to the thread to clear up my blunder. So sorry! The article I was referring to is by Brent Beach. I must have been moving too fast, as I read it in the same flurry of discovering your review of the Sharp Skate, in which I think you even mentioned some of Brent's research into sharpening.
Sorry about the error and any confusion I caused!

This is a link to Brent's article. The part that I was referring to is this:
Hi, Derek

thank you for responding to the thread to clear up my blunder. So sorry! The article I was referring to is by Brent Beach. I must have been moving too fast, as I read it in the same flurry of discovering your review of the Sharp Skate, in which I think you even mentioned some of Brent's research into sharpening.
Sorry about the error and any confusion I caused!

This is a link to Brent's article.

http://www3.telus.net/BrentBeach/Sharpen/bevels.html

His argument for micro back-bevels is convincing.

[David Weaver]

That is the kind of stuff I'm referring to when I say that I don't think it would harm an iron at all to tailor sharpening with a shallow back bevel and a shallow microbevel, and in fact would probably improve the quality of sharpening. I doubt that any competent sharpener here can create a materially superior edge without the bevels as they could with a 1 degree back bevel and a two degree microbevel (speaking with respect to smoothers).

I'm just on the fence about doing it with a 8/10 plane right now, but I should have a 45 degree plane to tinker with in a month or two, and I think i'll do that exclusively with it. The absolute only thing I think one would have to worry about was not overdoing it with the back bevel, or they will just end up polishing the entire ura at a 1/2 degree or 1 degree angle away from coplanar with the rest of the back - that would be no less work. However, the idea that you have to do "less" to keep the iron sharp isn't exactly an unwelcome thing, and if the angle was that shallow, it could be brough back in shape with uraoshi (lapping). The depth would be very limited.