setting japanese plane chipbreaker

[Patrick Chase]

Pat,

A functioning chip breaker is working the chip back against itself and using the blade as its backdrop to do this. The effect is more wear. When I need the chip breaker action of course this is the best of all worlds, but I certainly notice myself sharpening more often than I do when I have a more relaxed setting. More reason to set as required than to search for a one size fits all solution.

A simpler way to look at this is to ignore the exact chip formation mechanics and simply look at planing forces. As a few people have noted in this thread, tightening the cap-iron set increases planing effort/force. That increased force must be acting at or just above the point of the cut (since the rest of the plane<->wood interface hasn't changed), and will logically produce increased blade wear.

Brian's mechanical explanation makes sense, though I'm not 100% convinced that's the only thing at play. Wood is a complex material, and we're talking about stuff that occurs on relatively small scales.

EDIT: Steve Elliott has posted pictures from the Kato/Kawai study here, showing wear on the back of the blade just above the cutting edge, where the shaving turns as Brian describes, so I think it's safe to say that that wear mode is indeed a contributor :-)

[Kevin Neff]

Now that I'm re-reading that section, he says it depends on temperature and moisture content, too. And speed, I suppose. So maybe Stan is right to recommend trial and error. It may actually be easier than the theory.

I do not enjoy dealing with the additional blade. Now, I have reason to leave it out

[Patrick Chase]

Now that I'm re-reading that section, he says it depends on temperature and moisture content, too. And speed, I suppose. So maybe Stan is right to recommend trial and error. It may actually be easier than the theory.

My take: The theory is helpful to understand why we should learn to use double irons. It's also helpful to know when diagnosing problems, for example it's useful to be able to look at the shaving, figure out what "type" it is (keeping in mind that cutting mechanics can and do change within a shaving :-), and understand what factors go into determining that.

Theory isn't terribly helpful to understand how to approach a specific workpiece. Warren and Stanley are right on about that. You can stare at books and videos all you want, but wood is an incredibly complex medium that often defies analysis. As an engineer I can predict how common engineering materials will behave with reasonable accuracy, but planing wood is beyond me in that respect.

Empiricism is your friend, and the theory is mostly useful as a tool to help understand what the empirical results are telling you.

[Warren Mickley]

Pat Barry asked about the shavings from my planes. I used a smoothing plane on some sapele with very strong ribbon figure (interlocked grain); the shavings are limp. Savings from my trying plane are likely to be flat sheets, shavings from by jack plane are not. I think shaving thickness plays a roll here.

I think that if the double iron caused noticeable increase in force required, the cap iron is likely too close. As Brian noted, you really want to be on the risky side when placing the cap iron rather than the safe side.

I wrote this on another forum in 2007:
the double iron is a sophisticated instrument. For things to work well everything has to be just so. There is no shame in having trouble with it. If the idea of learning to use hot hide glue turns you off, the double iron is not for you. It takes a fair amount of practice to get a good feel for it. I can say that the benefits of learning are well worth the effort and I would not want to be without it.

When you are six years old it seems like a lot of effort to make the jump from tricycle to bicycle.

[Pat Barry]

A simpler way to look at this is to ignore the exact chip formation mechanics and simply look at planing forces. As a few people have noted in this thread, tightening the cap-iron set increases planing effort/force. That increased force must be acting at or just above the point of the cut (since the rest of the plane<->wood interface hasn't changed), and will logically produce increased blade wear.

Brian's mechanical explanation makes sense, though I'm not 100% convinced that's the only thing at play. Wood is a complex material, and we're talking about stuff that occurs on relatively small scales.

EDIT: Steve Elliott has posted pictures from the Kato/Kawai study here, showing wear on the back of the blade just above the cutting edge, where the shaving turns as Brian describes, so I think it's safe to say that that wear mode is indeed a contributor :-)

Looking again at the video, its pretty clear that 1) shavings want to curl naturally. 2) the chipbreaker strengthens this tendency of the shavings to curl. 3) The wear (judging from the video) is probably no significant difference at the edge with or without the chipbreaker. 4) The wear on the bevel is a function of the depth of the shaving and the chip breaker may in fact help reduce this wear due to the physics, but this is probably only true if the chip breaker angle + the blade angle are > 90. 5) If the chip breaker + the blade angle are less than 90, then the wear on the bevel is probably not all that much affected.

Interestingly enough, I didn't see any straight shavings in the video but that may just be more a function of the grain direction and the blade angle.

Even in the paper cited, I didn't see strong correlation between degree of wear with or without the chipbreaker.

Anyway, that is what I see looking at the video.

[Patrick Chase]

Looking again at the video, its pretty clear that 1) shavings want to curl naturally. 2) the chipbreaker strengthens this tendency of the shavings to curl.

Which video? The German one shows exactly the opposite of what you say (is it possible that you confused the close- and loosely-set cases?). The Kato/Kawai video shows the shavings curling no matter what. Note that in the Kato/Kawai video there was no mouth, and that may play a role since the shaving is quite weak after being broken and may take the shape of whatever path it follows.

Most of the people here who actually uses close-set cap irons has said the same thing: The cap iron tends to render the shavings "limp" and "flat" (Warren's words). It certainly doesn't "strengthen" anything, as it makes the shaving quite weak.

[Pat Barry]

Which video? The German one shows exactly the opposite of what you say (is it possible that you confused the close- and loosely-set cases?). The Kato/Kawai video shows the shavings curling no matter what. Note that in the Kato/Kawai video there was no mouth, and that may play a role since the shaving is quite weak after being broken and may take the shape of whatever path it follows.

Most of the people here who actually uses close-set cap irons has said the same thing: The cap iron tends to render the shavings "limp" and "flat" (Warren's words). It certainly doesn't "strengthen" anything, as it makes the shaving quite weak.

Yes, the Kato video. By strengthen, I meant increases the tendency to curl. Probably all depends on grain direction, shaving thickness, chip breaker angle and position, etc