chip breaker questions, what it really does

[Ron Petley]

I think the name chipbreaker is no really the name of that piece, but I could be wrong since I do not know another name for it.
It also might be a urban myth that the "chip breaker" really breaks chips. So my understanding now is that the "chip breaker" supports the plane iron (blade). I think the curl of the chip is created by the iron angle including the angle it is sharpened at, which is tied in with the mouth opening.
A lot of wood workers have told me otherwise as the name would imply , that it breaks the chip by making it curl up at a steep angle.
I use to set the "chip breaker" as close to the end of the iron because I was told so many time that was what it did and I figured it had to be right down their to do this. With it right down their it did affect the mouth opening for me. I was reading the thread about setting the mouth opening and thought of this question, not that anybody their said the "chip breaker" was breaking the chip.
Cheers Ron.

[Sam Takeuchi]

I think you sum it up pretty well. While I know that there's a study on this regard available online and shows pictures of planing machines taking different kind of shavings, personally I don't think the function of so-called 'chip breaker' (I call it cap iron) isn't so much about chip or shavings, but it serves for plane's structural function. If you look at bevel up planes (inc. block planes) and scrub planes, they don't have a problem without cap iron, and for that design, it'd be simply impractical to use cap iron. Even if it were possible, I don't see a use for it. In fact, before metal planes, wooden plane had a thick plane iron and a wedge, some Japanese planes didn't (and still don't) even have a wedge (the plane iron itself was tapered to wedge itself in). They all planed and shaved wood without problems assuming all were setup correctly.

Stock blades are thin and they flex. If they are held only at the middle of a blade, it'll chatter. So that's where cap iron comes in. Aside from providing functions for depth and lateral adjustment, it provides pressure point near the edge. Cap iron itself is still thin and weak, but a lever cap exerts massive pressure on two points, at the cam lever (or cam screw) and near the front end of cap iron. Because of cap iron's shape, plane iron is pressed against iron bed firmly, stiffening the blade by putting it under constant pressure. Basically clamping the plane iron down to the iron bed.

Improperly ground or milled cap iron provides partial pressure along the width of cap iron due to having bumps or ridges. Unsupported areas will have movement still, causing it to flex and chatter.

Replacement blades and cap irons are offered in thicker variations. Thicker the blade, less flexing the plane iron will have. Thicker the cap iron, more support and stiffer the blade can become. If metal planes can accept 5mm (0.200") plane irons, it can function without "chip breaker" just as well.

P.S. I'm half asleep, so I apologize for any omission and typo.

[Tri Hoang]

I think its primary function is to support the blade edge to reduce chatter. The chip still break without the chip breaker. At 3/16" thick, the irons on my bevel up planes cut smoothly without chip breakers. Same thing for the 1/4" irons in my bevel-down Knight planes.

[Joel Goodman]

I second the concept of the "chipbreaker" supporting the edge of the iron, near the sharpened edge -- in theory. On a BD plane the cutting edge of the iron is unsupported near the edge no matter how thick the iron is or how good the bedding is. And a little pressure near the edge can't hurt, but -- C&W and Brese make excellent BD planes without cap irons! So perhaps all it does is beef up a thin iron and provide a means of engaging the adjuster.

[Jim Koepke]

Chip breaker is just a name that caught on. Its main purpose is to allow the use of thin blades. At least that is what Leonard Bailey claims in his application for patent.

http://www.thestreethouse.com/Shop/Galoot/Leonard_Bailey/patent_pdf/Bailey_1867_72443.pdf

jim

[Joel Goodman]

Interesting -- this is as close to the horse's mouth as you can get!

[Bob Strawn]

I have experimented quite a bit with chipbreakers. I started out convinced that they did not do a lot, and I set out to prove that to myself. I was quite sure that a nice thick well tempered O1 blade negated any of the advantages a chip breaker might add. As a result of my experiments, now I am convinced that in a way, they are indeed chip breakers. For difficult wood, I still usually prefer a low angle bed with a bevel up, high angle blade, but for versitility, a plane with a chip breaker wins.

As you cut a slice into wood, the forces on the blade push it back and pull it into the wood. The lower the angle, the more the pull into wood is in effect and the lower the push back. High angle planes generally are better with difficult grain partially because the motion is more scraping and partially because the same amount of flex will not lower the blade as deeply into the wood as a low angle plane.

When a blade chatters, it is digging into wood and then pulling out often ripping fibers instead of cutting. If you take the chipbreaker and adjust it to where you can just barely see the blade project past it, the chip will indeed be flexed upward more sharply. This alters the forces on the blade where there is no longer downward pull at the very tip. This also reduces somewhat the tendency for a blade to follow the grain.

With good grain in the right direction and a sharp blade, a chip breaker may actually increase the work without any visible advantage. For more difficult grains, it can seriously reduce tear out.

As you move the edge of the chipbreaker closer to the edge of the blade, you begin to develop a type 2 chip. The crinkly kind that flakes apart. This allows a normal plane to act very much like a high angle plane. In this configuration, it takes quite a bit more force pushing for the amount of wood removed, but with a sharp blade and a matching well fiittled chipbreaker, the action is quite a bit improved. Less tearout is a wonderful thing. If you push this same plane almost sideways, so the actual swath is slightly less than half the width of the plane blade,The sort of grain you can cut without tearout is greatly increased.

Bob

[Tim Put]

Both supersurfacers and rotary veneer slicers sometimes have chipbreakers that actually break chips.

An average chipbreaker in normal use in a handplane gives only structural advantages. A very closely set, very finely shaped chipbreaker can be useful.

http://planetuning.infillplane.com/html/chipbreaker_study.html

[Joel Goodman]

Does anyone else think that the article mentioned would seem to show an advantage to the Stanley style "chipbreaker" as the professor recommends a chipbreaker with a 50 degree angle -- the Stanley type curves sharply away from the plane iron while the newer LN and Hock have a 25 or 30 degree angle? Or is this negated by the need to position the Stanley further from the cutting edge so as not to block the mouth and cause clogging?

[Ron Petley]

Gentleman, thank you, the level of knowledge here is most singular.
The study article is also outstanding..
The modified cap iron part is very good stuff that I will have to give a try.
http://planetuning.infillplane.com/html/tuning_infill_planes.html

Cheers Ron.

[Jim Koepke]

I have experimented quite a bit with chipbreakers.

[snip]

As you cut a slice into wood, the forces on the blade push it back and pull it into the wood. The lower the angle, the more the pull into wood is in effect and the lower the push back. High angle planes generally are better with difficult grain partially because the motion is more scraping and partially because the same amount of flex will not lower the blade as deeply into the wood as a low angle plane.

[snip]

Bob

Bob,

Thanks for the great research and information. I have always felt there was a tendency for my low angle block planes to "dig in" when going with the grain.

It is one reason I have not really jumped on the LA or BU bandwagon. I am sure they work for others, but so far my old Stanley/Bailey planes have been able to do the job.

jim

[Bob Strawn]

I would not discount the low angle bevel up planes. A low angle bevel up plane with a high angle blade, can do amazing work with a wide mouth. They really are extraordinary.

The downside of running a plane bevel up, is that you end up having to remove more metal when sharpening. The wear seems greater and the shape of the wear is worse.

http://battlering.com/woodworking/images/Squirrely.jpg

This plane is very low bed, and a very wide mouth. Due to a secondary bevel on the blade, it is about a 60 degree angle relative to the wood when planing. It works fabulously. Almost all the forces are pushing the blade back and not pulling the blade down.

Some wood just seems to clog a tight mouth no matter what you do. The mouth on this plane is pretty well clog proof.

Bob

[Joerg Bullmann]

Just recently I came across the Kawai/Kato chip breaker video and related writeups:

http://giantcypress.net/post/23159548132/this-is-the-full-version-of-the-video-created-by
http://planetuning.infillplane.com/html/chipbreaker_study.html
http://www.woodcentral.com/articles/test/articles_935.shtml

Scouting about I found this thread here and I just wanted to drop off a few thoughts/observations.

To me there seem to exist two entirely diffent chip-breakers: Bailey type and Kawai/Kato type.

- the Bailey type's idea is: support the iron and reduce vibration and chatter
- the Bailey type will work with a narrow mouth which should help reducint tearout
- the Kawai/Kato type's idea is: push the shaving back into the stock, thereby reducing tearout.
- the Kawai/Kato type will not work with a narrow mouth, as it will cause lots of clogging

Did I get the above things right?

I now wonder which of both will work better altogether. I have an old and worn wooden plane here (which I will have to flatten and true first) and maybe I'll get around to fitting a Kawai/Kato type iron and breaker to it and then see what shavings in difficult wood are possible.

Cheers,
Joerg

[george wilson]

Your first link does not work.

[Joerg Bullmann]

Your first link does not work.

Hmm, just tried again and it seems to work fine here. Are you possibly sitting behind a filter-wall? Those can be annoying.

[David Weaver]

Before anyone rips me about the tearout in the picture of my article, note the credit for the pictures. I was not able to get pictures, but you should be able to plane a board, including one like that mahogany with no tearout at all. I think Ellis just did a before, wound the chipbreaker down close and took another pass or two and wasn't focusing on eliminating tearout, just reducing it. Still useful at that level, but it is my intention in general to do nothing after planing other than apply finish, or maybe burnish the wood surface with shavings or something if you feel the finish calls for it.

Anyway, the only thing limiting what you can do with the angle of the second iron relative to the first is, well, two things:
1) on really soft woods, you don't want a steeply pitched chipbreaker right at the surface pushing the fibers back into it. You can see some crushing in the second mahogany picture due to just that.
2) most importantly, the ability of a given plane to have clearance to clear a shaving with a chipbreaker at a given setting. Close set with a closed mouth and a high pitch isn't going to clear in a lot of planes, and you have to decide whether you're going to reduce the set (increase the distance from the end of the iron to the front of the chipbreaker), reduce the angle of the chipbreaker's attack or open the mouth of the plane to let shavings through.

For option #2, I would thus far prefer to open the mouth and keep the cap iron set where I want it. I haven't found a super steep cap iron (like kato used) to be necessary for anything. 45 to 50 degrees in the angle of attack at the front of the cap iron has worked very well, fed well, and not caused issues with smashing the chip back into the surface of the wood being planed causing the crushed look on something like quartersawn pine.

As far as types, the type of chipbreaker doesn't matter. Whether it's a machine like kato used, or whether it's an old cap iron or a stanley style cap iron or a new "improved style, they all work the same if they are set up properly.

If you need to narrow the mouth for anything, then the chipbreaker is not properly set or tuned. Your best plan is to get to the point where you use a tight mouth on a single iron plane, but on one without a chipbreaker, it is only closed to a distance where it will feed anything that you put through it at any chip thickness you might use. There's no reason to have it any closer, because it's not needed to mitigate tearout and will be counterproductive with feeding.

Bailey's patent talked about stabilizing thin irons, which his chipbreaker does, but it shouldn't be overlooked just how good it is at mitigating tearout when used properly, which was common knowledge at the time and something that would be taken for granted.

[David Weaver]

By the way, we're talking with a lot of words when we describe this stuff, because it's relatively specific, but when you start experimenting with the iron and cap iron, you get a setting or two that works and as you work with different woods, it becomes completely trivial. It's not as differentiated or complex as it sounds. Sort of like any function in hand tooling, it's trivial once you do it a little bit.

[Chris Griggs]

I didn't realize you had written/published an article on this Dave. Good stuff and very well written. I'm glad you did that - it'll be a great reference for a lot of folks.

[Jessica Pierce-LaRose]

David - I've had the effect with close set chipbreakers where the shavings get scrunched up and accordioned - I set the chipbreaker back a bit and things were fine, but it occurred to me, all I've been working lately is poplar. Sooner or later I'll get back to working hardwood and experiment a bit more. Any comment on whether the settings that work well in hardwood would display this scrunched up behavior in softwoods, or do you think I'm too close in general? Just curious - I suppose it doesn't really save me any time either way, but I've got a pretty good eye at this point for just what point I start getting that behavior in poplar, and wonder if I should try starting there in hardwood or move back. . .

[David Weaver]

I think in most softwoods, the cap iron doesn't need to be set so close to crinkle the shaving, and that you run the risk of making the surface look like the chip has been forced back into it (not that 99.99% of the population would ever have any idea of what that looked like).

I kind of prefer (maybe I said this in the article, it was a while ago) just keeping the cap iron out of the way so that on a heavier shaving it straightens out the chip some, and you can look at the chip and see that it's been "worked" by the cap iron.

I think that's pretty much true in hardwoods, too. If you have tearout in hardwoods at that setting, you can move it a little closer. that's probably something in the range of just under a hundredth of the edge on a stanley smoother, but I've never measured so I couldn't tell you anything other than what the chip thickness is when it really starts to look worked by the cap iron (and that's in the .006" range).

I can say that I haven't yet found a wood where my 55 degree infill with a .003-.004" mouth and a single iron will outperform my properly set millers falls #9 with a buck brothers $3 iron in it. the latter will leave a brighter finish, too. I was just too dense long ago to figure out why I wasn't having the same experience warren mickley said he has.

That coarse type smoother shaving is very useful for someone who dimensions wood by hand, but it might not be so useful for someone just removing plane chatter, and the objective all the time is still always to plane with the grain so that any plane would do the job. Sometimes glue joints, etc on panels just don't allow it. I'd rather have a good color match at a glue joint on a panel of medium hardwood (esp. something like cherry) than a scorched earth view of the grain having to be identical at the line. A lot of the wood I get from the local supplier just really isn't that good where it's dead downgrain or the opposite, anyway.

Anyway, set the cap iron off a little so that it prevents "really bad" tearout and so that it doesn't bull your around with the plane quite so much, and move it forward to that really close set only if you need to.

[Joerg Bullmann]

I really am getting curious now to experiment and try out a steep chip breaker and see how it compares to other setups. Thanks for your detailed response.

Cheers,
Joerg