Chris Schwarz's Blog

Reconsidering Chipbreakers as Not Totally Evil

Here is a breaker installed less than half a millimeter from the cutting edge. Look closely. The line under the cutting edge is secondary bevel on the chipbreaker.

I have always disliked chipbreakers, which clog a handplane all too easily. But tonight I dislike them a little less.

After the recent spate of discussions about a series of Japanese films on chipbreakers (here is the complete and translated film) and some encouragement from woodworker David Charlesworth, I decided to experiment with the position of the chipbreaker on my bench planes.

The result was incredibly impressive. But I’m getting ahead of myself. First, a bit of history and theory.

Planes didn’t always have chipbreakers, and they did a fine job of making some of the most beautiful high-end furniture in the Western world. But after their advent, writers sang their praises on a regular basis as a great improvement.

I never understood it. According to early books, you set the tool’s chipbreaker close to the cutting edge of your handplane, presumably to help reduce tearing. When I first started using planes, I followed those instructions, but I didn’t see much benefit. What I did experience was a lot of clogging.

So I backed the chipbreaker away from the edge (about 3/32″)  and focused on other ways to reduce tearing – the cutter’s sharpness, a tight mouth and the angle the edge was presented to the wood.

The recent discussion of the Japanese films (which are not new), made it clear to everyone with an Internet connection that the chipbreaker had to be a lot closer to the cutting edge than I ever suspected. How close? The answer is itself a question: How close can you get it?

Today I explained these ideas to a class of students I am teaching at the Dictum GmbH school of woodworking in Germany and asked all of them to help me examine this idea by setting their breakers as close as possible to the cutting edge.

We set them by screwing them down tight and tapping them forward with a hammer – getting as close as we dared or as our eyesight would allow.

The first results were interesting. The shavings we produced were surprisingly crinkled. Bengt Nilsson, a colleague of mine in the class, produced shavings on bubinga that looked like smashed up bacon.

With our first experiments with chipbreakers on Tuesday the bubinga shavings came out looking like cooked bacon.

But the surfaces of the wood looked nice. Other students had similar success – with no real tearing on a wide variety of species, everything from Scots pine to walnut to oak to beech to the bubinga. And this success was regardless of grain direction.

Not satisfied, I took my chipbreaker to the sharpening room and honed a 50° secondary bevel on my chipbreaker. I polished it to #8,000 grit as well (why not?).

That changed everything in the way the shavings looked. Instead of looking like a crinkle fry with a case of the bends, the shavings flew out of the mouth with a minimal amount of distortion. The surface of the wood looked as good as ever. Even on knots, reversed-grain bubinga, quartered and messed-up oak – you name it – the results were very good.

And this was in planes of all sorts, from a Groz try plane to a Veritas jack (bevel down), to a Kunz smoother, to a Lie-Nielsen No. 4. Plus other sizes of all these brands. The only plane that resisted the tuning was a Lie-Nielsen No. 6. With the breaker set that close, the blade-adjustment dog kept slipping out of the breaker. A new breaker would fix that in a heartbeat.

Pieces of wood that I had been scraping the day before were easily planed with the tight chipbreaker setup. The only change in the setup was the position of the breaker.

Of course, I need to do more work at home on woods that are even nastier (roey mahogany comes to mind). But count me as seriously impressed. Give it a try in your shop. It’s a five-minute modification that might change the way you set up your handplanes for the rest of your days.

— Christopher Schwarz

Now I might to update my book “Handplane Essentials,” which deals with all aspects of these tools. The book is still a good resource for learning to sharpen, tune and use all sorts of planes. It’s hardbound and printed in the USA.

27 thoughts on “Reconsidering Chipbreakers as Not Totally Evil

  1. HighRockWoodworking

    Thanks Chris. Very interesting post. I love hand planes (metal and wood) and have built quite a few wooden planes myself, but the chip breaker has always been akward. I think it is time I play around with the settings a little more and try your method of honing. Wish me luck!

    Chris Adkins

  2. Bill Rittner

    I learned the benefits of a tightly set cap iron some years ago while following a group of Galoots on the old tools mail list. These guys were expeimenting with cap iron and mouth settings in an effort to reduce tearout. During the discussion one guy mentioned that if he had his cap iron set extremely close to the cutting edge he could plane in any direction regardless of the mouth opening. This opened my eyes. I tried it and since then I have been using this info and rarely adjusting my mouth settings.

    Now I need to experiment with the cap iron bevel.

COMMENT