Chris Schwarz's Blog

More Experiments with Chipbreakers

This week I’ve been surfacing a lot of wood by hand, from pedestrian sugar pine to funky metals that have wood-like properties (e.g. purpleheart). And all the while I have been testing, testing, testing things with my chipbreakers and the cutting angle of the iron of my handplane.

Huh? You might say. Yes, there might be a relationship.

So I’ve been up at Lie-Nielsen Toolworks in Warren, Maine, this week to teach classes, shoot a video and demonstrate at the company’s open house. During the evenings, I’ve been debating a lot of theories about wood failure with Deneb Puchalski and Thomas Lie-Nielsen. Here are some highlights.

1. Why does setting the chipbreaker crazy close reduce tear-out? Deneb of Lie-Nielsen has a good theory. He thinks that a closely set breaker “fools” the wood into thinking that it is being planed by a high-angle plane. So a 45° plane with a 25° breaker suddenly acts like a 70° plane. This makes sense.

2. Do you need a tight mouth with a close-set breaker?

3. Do you need a high-angle plane with a close-set chipbreaker?

4. What effect does honing the breaker have? And what angle should you use?

So during the last week, here’s what I did. I worked with two smoothing planes. One with a 45° frog. One with a 55° frog. I honed the cutting edge the same and tapped the chipbreaker as close as I dared to the edge. I also did some work with a bevel-up jack plane honed at 50° so it had an effective cutting angle of 62°. All the planes had mouth apertures of 1/16”, which is pretty wide open.

On the smoothing planes I honed a 50° angle on the chipbreakers. So if Deneb’s theory was correct, I actually had three different planes. One was cutting at 62°. One was at 95°. The third was at 105°.

Then Deneb, Dave Jeske of Blue Spruce Toolworks and I put the planes to use on a variety of woods. We tried reverse-grain cherry. It was no challenge for any of the planes. Then curly bird’s-eye maple, planed against the grain. Again, no problem. Ancient fossilized purpleheart. Nope. No difference. Then a board that we were told was unplanable: big furry, roey mahogany.

Again, all the planes handled the wood with no real problems.

Finally, I pulled a piece of wood out of the trash. It was cherry with a tight swirled knot in it. There was a crapload of grain reversal around the knot. Lots of quartersawn grain rippling across the face.

In other words, it was fit to be burned.

After dressing the wood with a toothing plane we put the 62° plane to it. It cleaned up all of the board except a narrow band of tearing along one of the quartersawn ripples. Then we took the 95° plane to it. No joy. But the 105° plane cleaned it up nicely. And it left a typical planed surface – it didn’t look like it had been scraped.

So perhaps Deneb has something. Or my 105° plane is haunted by a small dwarf or troll.

— Christopher Schwarz

Read more on my chipbreaker experiments here.

20 thoughts on “More Experiments with Chipbreakers

  1. knot2serius

    Chris: You put a 50 degree micro bevel on the chipbreaker and apparently set the chipbreaker as close to the front of the blade as possible, whereas the video suggests an 80 degree angle on the chipbreaker and backing it off to 2 or 3 mm. Why the difference? Bill Lyman.

  2. randyk

    I have a question about this method. I have several older planes and plane irons and, as a consequence, use the ruler method to sharpen the irons. When I tried getting the cap iron crazy close the back bevel caused problems. I assume that the ruler method can’t be used under these circumstances.

    Also, it seems to me that the true test would be to grind a 105 degree bevel on a bevel-up plane iron and try it.

    Finally, I wonder how hard it was to push the “105″ degree plane?

    1. JWatriss

      A 105 degree angle on a bevel up wouldn’t work. It would simply slide, as it would be a bevel that tilts up and away from the wood, like the front of a toboggan. The edge still needs to be at a workable pitch, the cap iron is there to bend the shaving further forward. I’m still not clear on whether it’s the pitch or the cap iron angle that was the deciding factor on that cherry knot, but I do have an extra cap iron on hand to test that myself.

      As long as the cap iron is shaped so that it will come down and the edge will meet the face on the iron, your plane should work. On that note, an older style chip breaker might be better.

  3. JWatriss

    Cool results, but this is where the theory gets put to the Schwartzian Hammer…

    If the total angle of the pitch and cap iron is the deciding factor, you *should* be able to get similar results by putting a 60 degree bevel on the cap iron for the 45 degree smoother.

    Does it work just as well that way, or is the pitch/ relief angle still a relevant factor?

    What about AFTER you hit the plane with a hammer?

    1. Zeb

      Love to hear a response to this. Does seem like a huge difference between having different frog angle setups (usually on multiple planes) versus just having a couple different chip breakers with different bevel angles.

  4. Bill Lattanzio

    While this is all pretty interesting I just don’t have enough time for it. I get little enough time in the shop as it is and when I do I want it to be spent making furniture. If I start worrying about exactly far the iron is to the chipbreaker I’m going to lose it.

      1. Bill Lattanzio

        I should have different phrasing. Time may not have been the right word. I just mean that I set the chip breaker where I think it looks right and get to work. Maybe I’m the antiwoodworker but I’m trying not to think too hard when I’m in the shop. I think enough at work. I feel the same way about sharpening chisels. I don’t worry about the angle, just that it’s consistent everytime. I hope you aren’t offended. I always like your advice. I read the Anarchist Toolchest…twice…I may even read it backwards just to be a hotshot.

  5. tahoetwobears

    Chris,

    What’s crazy close? Can you quantify that a bit more? I’d like to try this as well, but want a starting point.

    Thanks,

    Mike

    1. Christopher SchwarzChristopher Schwarz Post author

      You hit the breaker until it looks like it is about as far away as a human hair.

      I thought this would be hard. It is not. Repeat: It is not.

      I urge everyone to stop “thinking” about what is happening and try it.

  6. adrian

    Based on the video and all the discussion in the forums, if you put the chip breaker too close to the edge, it makes performance worse. That would mean that it can’t be simply acting like a higher angle plane. Too close, in this case, is something like 0.1 mm. It needs to be more like 0.2mm or 0.3mm. I got the impression that this worked because the shaving was levered up and this applied a downward force where the shaving was still in the wood. That downward force helped prevent tear out. Have you guys watched the videos showing the chip formation with different geometries? It’s reproduced here at the top: http://www.solidwoodmachinery.com/supersurfacers.htm and if you scroll all the way down to the bottom there is a summary of the different conditions.

    mbholden: if they recreated a scraper then why did the surface look planed instead of scraped?

    Bernard, It sounds like they got better results with the 55 deg bevel down plane with the cap iron than they did with the 62 deg bevel up plane. So how would this support the notion that bevel up is best? Bevel up planes don’t have a chip breaker at all. There is nothing acting like a chip breaker in these planes. In a bevel down plane, the chip breaker causes the shaving to curl up. It changes the direction of the shaving after it is cut. A bevel up plane is like a bevel down plane with the chip breaker pulled back: nothing changes the direction of the chip after it is cut. The thick blade does not, in any sense, act like a chip breaker.

  7. BLZeebub

    Ahh, experience… love it when reality sets in, huh? The tool chest of experience fills up for each of us in its own time. In such, that chest can become cluttered with gadgets and gizmos and the idea that, “Gee, if I only had one of those I could…”

    What I want now in my tool chest(s) are only the good tools. The ones that I actually USE. But foremost and best of all is the knowledge that I can gitter-dun that is the tool I most cherish. Who gives a rip about whisper thin shavings unless that in itself is the end product? Last time I checked, if I were busy making a days worth of .001 of an inch shavings and all I had to do was increase the thickness of that shaving by a factor of ten so I’d have one tenth the shavings to sweep up at the end of the day. Hmmmm…

  8. chpcrvr

    Since the wood has already been cut by the time it reaches the chip breaker, even if it is set very close to the edge, I don’t see how it can ‘effectively’ change the cutting angle (or fool it). I would argue that you are improving the chip handling (breaking) as it passes over the chip breaker.

    On page 122 of “Traditional Woodworking Handtools” by Graham Blackburn he states, “For the capiron to be effective it must be positioned as closely as possible to the cutting edge in order to break the shaving at the earliest opportunity……If the front edge of the capiron is not perfectly smooth – indeed, polished – it can impede the shaving’s smooth passage even while it is being broken”.

    By shaping the edge of the capiron and polishing it, it seems you are just improving it’s function and not actually changing the effective cutting angle.

  9. mbholden

    Why should this be such a revelation?
    Are you not simply recreating a scraper? Which is known to be relatively impervious to grain direction.

  10. Bernard Naish

    As bevel up planes do not use a chipbreaker, because the thick iron performs this function, they clearly have a perfect chip breaking set up. Is that correct? If so I am beginning to think that the best choice for a smoother would be a bevel up plane. Love to hear other comments.

  11. tjhenrik

    Although I might not admit it in public (at least in co-ed public), I would have loved to be a fly on that wall. Sounds like some interesting crazy fun. I have played with different angles honed on my low angle jack and been impressed. I’d be interested in hearing more about any modification you decide to use on your chip breakers.

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