chip breaker questions, what it really does

[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