There are three things extremely hard: steel, a diamond, and to know one’s self.
Benjamin Franklin
In this fifth post in our series about the Japanese handplane, we will discuss a single component of the handplane, the chipbreaker.
Professional woodworkers that use handplanes daily usually have this simple widget thoroughly figured out, but your humble servant has been asked to clarify why the chipbreaker is necessary and how to make it work so many times recently that I can no longer gracefully avoid publishing a more complete, BS-free explanation for the benefit of our Beloved Customers, may the hair on their toes ever grow long.
As always, this post is intended to provide a bit of insight, or at least a different viewpoint, to our Beloved Customers, many of whom are professional woodworkers and Luthiers.
This is a longish article. If your humble servant was a lazy man I would simply state stand-alone conclusions as have so many with half-baked knowledge of handplanes, and leave it up to Beloved Customer to figure out the why of things on your own, but that would be boorish behavior.
Even if you already know everything there is know about the chipbreaker, you may still find a new crunchy, scrumptious tidbit or two in this mess of scribbling if you look.
Factors Critical to Controlling Tearout
The sole purpose of the chipbreaker is to control, and whenever possible, completely prevent the unsightly and wasteful tearout that often occurs when using a handplane to surface wood. We will examine the causes of and some solutions to tearout below, but let’s begin this discussion by examining factors critical to controlling/eliminating tearout that actually take precedence over the chipbreaker. Your efforts to control tearout should always begin with these factors. But first allow me to share a story.
Back in the mists of time when dinosaurs roamed the earth and your humble servant was but a slender young man with much more hair on his head and far less dignity under his belt, I liked to think I had a sound understanding of both steel and wooden Western-style planes, but I knew little of Japanese planes. Later I was blessed with the opportunity to learn about the Japanese handplane in Japan from master craftsmen.
As is the case with excellent craftsmen of all ages, these gentlemen talked very little but assigned me what seemed at the time to be daunting work assignments.
While they would allow me to examine their tools and observe their techniques in-person, the only instruction they would provide initially were two or three-word critiques of my frequent mistakes. I understand now that they were kind gentlemen, albeit 40~50 years older than me, but at the time this apprenticeship-style of training was frustrating. Only when I showed true progress would their answers stretch to 5 or 6 words because, unlike your humble servant at the time, (here is wisdom) they understood that lessons learned through many failures and a few success are learned best.
The first assignments given me were to sharpen everything in the workshop that would hold still long enough to touch with a stone, from axes and adzes to chisels, handplanes and even saws. This went on for months. They weren’t being mean, just wise, because sharpening is the first and most important woodworking skill. Only when I had demonstrated competence in all aspects of blade preparation and sharpening did they share further light and knowledge with me because any sooner would have been a waste of their time, you see.
They then assigned me the task of making an old-fashioned Japanese handplane, one without a chipbreaker, entirely by hand using a hand-forged blade by Mr. Masato Yokosaka. This was before he and his products became famous, BTW. This was an educational effort, one that I magnificently failed twice before finally getting it right, but it taught me the three most important factors in reducing tearout in handplanes, whether with wooden or steel body, with chipbreaker or without. Unlike my curmudgeonly old masters, I won’t insist Beloved Customer stop reading until they have mastered all three of these factors, but master them you must if you are to achieve excellence with the handplane.
Factor 1: The blade must be sharp. This factor depends on the quality of the blade and the skill of the person who sharpens it. We have a series of 30 posts about sharpening Japanese woodworking blades Beloved Customers may find beneficial. The series starts with this LINK.
Factor 2: The mouth opening (gap between the sole and the cutting edge) must be as tight as practically possible and still pass shavings. Please make an effort to truly understand what this means, because it is not always easily accomplished. Of course, the mouth opening of a super finishing plane intended to take transparent shavings will of necessity be narrower than that of a plane intended to dimension boards by taking thicker shavings; Horses for courses;
Factor 3: The area on the sole directly in front of the mouth opening, a strip across the entire width of the sole of the plane and perhaps 3~6mm wide, must be true and flat and apply even pressure on the board being planed right up to the last few microns of the mouth opening. This is not an exaggeration. Much else can be out of wack but if this is right the plane will usually cut well.
Why are these three factors critical? To begin with, a dull blade won’t sever fibers cleanly but will tend to tear contrary fibers up and out of the board’s surface, the very definition of “tear out.” Can’t have that, ergo, Factor 1.
Since the soles of handplanes wear and consequently the width of mouth openings change with that wear, Factors 2 & 3 are dependent on the team of craftsmen that originally made the handplane as well as the craftsman/owner that uses and maintains the handplane over its lifetime. That’s you, Beloved Customer, so please pay attention, learn the lessons and develop the necessary skills.
Indeed, Factors 2 & 3 act in unison to control the movement of contrary fibers immediately before and after they contact the blade directing them into the cutting edge to be cleanly severed by the sharp blade (Factor 1), while at the same time serving to bend, buckle and weaken those fibers that would otherwise tend to develop a lever arm and tear out below the surface of the board. If this doesn’t make sense to you, please give it careful thought because you must figure it out if you intend to become proficient with handplanes.
These three factors are bedrock essential to controlling tearout regardless of the type of handplane in question and whether it has a chipbreaker or not. Few new planes, whether made of wood or steel, meet these conditions. And after regular use, resharpening and adjustments become necessary, so Beloved Customers are strongly encouraged to understand how to evaluate these three factors in your handplanes and learn how fettle them. We will address the necessary techniques in future posts, but it will take more than just reading, so consider it an assignment. Indeed, expect to screw it up royally at first and learn from your mistakes, just as your humble servant once did.
The Chipbreaker & Historical Lumber Processing Techniques
To better understand the chipbreaker, Beloved Customer may find it useful to understand a few historical factors about the wood they are shaving and some background about the tool used for making those shavings.
Before the proliferation of the large rip saw, and especially the water-powered sawmill, the only practical method of producing boards and beams from logs was to “rive” (split) them out using wedges and axes. This is the same worldwide.
The thing about logs is that not all of them have grain straight enough to produce useful lumber when riven. Large, long, straight, old-growth trees are most efficiently processed. As nearby old-growth primeval forests with large, straight trees were cut down and premium-quality logs became harder to come by, much construction and shipbuilding came to rely on more economical beams, posts and boards sawed from logs with wonky grain.
Riven wood has two convenient advantages. The first one is that, because the grain of the lumber is relatively straight and continuous, grain runout is reduced, making it somewhat stronger structurally. And second, the occurrence of tearout when surfacing riven lumber is often less than what typically occurs in sawn lumber.
Unlike a team using axes and wedges, large rip saws in the hands of sawyers made practical through the proliferation of inexpensive, reliable steel, and especially the water-driven sawmill, could more easily and quickly cut long, straight boards and beams out of most any log regardless of grain direction. Consequently, logs that would have been rejected before the days of the sawmill can now be readily processed reducing the man-hours/cost of producing lumber significantly. On the other hand, the grain direction of lumber produced using large saws and sawmills tends to wander everywhere increasing runout and making the job of cleanly surfacing the boards more difficult for subsequent craftsmen. This is the situation we face now.
We don’t know when or where the chipbreaker was invented, or how the concept spread around the world, but it’s a safe bet to assume its ability to calm the wild grain of sawn lumber during surfacing was one reason for its popularity. At least, that’s how it went in Japan. And wood is wood no matter where you are.
Why Does Tearout Occur?
Let’s next examine some basic causes of tearout.
Please recall that wood is comprised of various types of cells, each with a job to do, but most of those that eventually become lumber specialize in transporting water up from the ground to the leaves, and nutrients formed in the leaves to the rest of the tree. Transporting literally tons of water daily from the roots far up into the sky is the job of continuous groups of cells that form what are effectively continuous waterpipes connecting the roots to the stomata in the leaves. In a living tree these pipes have semi-flexible cell walls, and while they mostly grow parallel with roots, limbs and trunk, their shape is influenced by wind, rain, snowload, shifting soil, microbes, bugs and ever-changing exposure to the sun over the life of the tree, so they are seldom perfectly straight. Indeed, once dried, it’s partly the changes in direction of these tubular cells, often called fibers, that gives harvested lumber its beautiful grain patterns and shimmering chatoyance.
When planing with the grain, the blade severs fibers which are oriented either parallel with or sloping up to the board’s surface and angled in the plane’s direction of travel producing pretty shavings comprised of relatively short, flexible segments of fiber.
But when planing against the grain, the blade must sever fibers that are diving down into the board. Instead of consenting to being cleanly severed, often these longer, more rigid fibers tend to ride up the face of the blade, bridging and avoiding the cutting edge.
When this happens, instead of severing them cleanly, the blade tends to lever these longer fibers up out of the board’s surface until they suddenly break off below the surface of the board leaving a rough uneven surface. This damage is called “tear-out” in English and Sakame (sah/kah/meh 逆目) in Japanese, which translates directly to “reverse grain.”
How Does the Chipbreaker Work?
Whether the handplane in question be Western or Japanese in design, the chipbreaker, or Uragane 裏金 (oo/rah/gah/neh) as it is called in Japan, seems at first glance to provide little benefit in exchange for the added weight and complication. Indeed, if all the cuts you make when planing wood are in the direction of the grain (id est fibers either oriented parallel with, or rising up to, the surface of the board and angled away from the direction of the cut), the chipbreaker will be about as useful as a lace brassier on a boar. But wood grain is seldom so cooperative, donchano.
With the addition of the chipbreaker, and in combination with the three factors listed above, those contrary fibers that try to bridge and ride up the face of the blade without being severed immediately run smack dab into the abrupt face of the chipbreaker thereby bending and buckling them and preventing them from bridging and developing the lever arm necessary to break them off below the surface of the board.
At the same time the collision with the chipbreaker redirects many of these mischievous fibers into the cutting edge to be severed, thereby preventing, or at least reducing, nasty tearout.
Bless us and splash us, preciousss! What a wonderful counterintuitive thing!
To better understand how the chipbreaker works, I highly recommend Beloved Customers devour, like starving little piggies, the video titled “Influence of the Cap-iron on Hand Plane,” Created by Professor Yasunori Kawai and Honorary Professor Chutaro Kato, Faculty of Education, Art and Science, Yamagata University (with subtitles). Much will come into focus after watching this.
Downsides to the Chipbreaker
While your humble servant has written glowing things about the chipbreaker, I do not suggest all is blue bunnies and fairy farts because the chipbreaker has some downsides:
- The chipbreaker adds weight, complication and cost;
- The impact of wood fibers on the chipbreaker produces friction heat and consumes energy whether cutting with or against the grain. This energy loss is not insignificant;
- When cutting with the grain, the chipbreaker adds little benefit while tending to reduce the luster of the planed surface;
- To be effective, the chipbreaker must be setup, tuned, installed and maintained properly, requiring the user to have adequate knowledge and to put forth effort periodically.
Despite these downsides, your humble servant believes, as have millions of craftsmen over untold centuries, that the chipbreaker is a component worth mastering.
Alternatives to the Chipbreak
In light of the gains and losses associated with the chipbreaker, it would be short-sighted, indeed amateurish, to assume it is always necessary, and just as short-sighted and amateurish to assume it is never necessary. So let’s examine some alternatives next.
Alternative 1: No Chipbreaker
The first alternative to the chipbreaker we must consider is, of course, no chipbreaker. Indeed, if you always plane with the grain of the wood, as mentioned above the chipbreaker adds no value while wasting energy. Indeed it may even reduce the quality of the finished surface’s appearance.
In the case of the Bailey pattern plane or other styles with cap irons and the chipbreaker and blade attached to each other by screws, using the plane without the chipbreaker is inconvenient. But in the case of Japanese plane, the chipbreaker can be easily and speedily removed without influencing the cutter. The resulting finish created by the plane may or may not be improved, but the force required to motivate the tool will absolutely decrease. Sadly, such cooperative wood can be elusive.
This is an excellent solution, one I highly recommend to Beloved Customers.
Alternative 2: High Bedding Angle Without a Chipbreaker
Another option with a long history worldwide is to install the cutting blade in the plane’s body at a higher bedding angle, perhaps 50~55˚+. Combined with a sharp blade, tight mouth and solid uniform contact/pressure between the board being planed and the area of the sole directly in front of the mouth opening, the more abrupt change in direction forced on shavings by this high-angle blade will then tend to buckle the long contrary fibers on its own without a chipbreaker. But no guarantees.
While a high bedding angle does indeed tend to reduce tearout, adding a chipbreaker is a proven way to further reduce tearout in woods with contrary grain even more.
The one constant downside to a high bedding angle is the extra energy one must always expend to motivate the plane.
Alternative 3: Bevel-up Handplanes Without a Chipbreaker
Another alternative is the “bevel-up” planes that have become popular in recent years. This style of plane is not a new solution. I own some and have used them, but other than the block plane versions, I regret falling prey to specious marketing claims spouted by shills.
Amateurs like them because parts are fewer, maintenance is easier, and the necessary skills one must acquire are fewer.
One gentleman boldly informed me that he believes bevel-up planes to be superior to all others because he would rather spend the time it takes to master the chipbreaker on making wooden objects. My mind boggled like a weasel binging on crystal meth….
Bevel-up planes work in exactly the same way high bedding-angle planes do by presenting a steeper angle for contrary fibers to climb causing them to either be severed or to buckle instead of tearing-out. This assumes, of course, that the blade is sharp, the mouth is tight and contact between the board being planed and the area of the sole directly in front of the mouth opening is uniform.
Sadly, the efficacy of this action is no more consistent than the high-angle blade without a chipbreaker discussed above.
The downside to the bevel-up plane is that the additional, more-consistent results afforded by a well-tuned chipbreaker are, like heaven’s pearly gates to a San Francisco politician, forever unattainable.
Alternative 4: Back-bevels
Another alternative is the quick and dirty back bevel applied to the ura or face side of the cutting edge, as discussed in a previous post. This works for the same reason the high-angle blade does, but it is not an effective long-term solution, and certainly qualifies as tool abuse in the case of Japanese handplanes IMHO. Consider yourself well and truly warned.
I highly recommend Beloved Customers use planes with chipbreakers and learn how to sharpen, properly setup, maintain, and adjust them for maximum results. It’s the way advanced professional woodworkers with real skills get the job done.
Keys to Making Chipbreakers Work Effectively
The following is a condensed list of tasks Beloved Customer needs to accomplish to get consistently good results from their chipbreakers. We will discuss all these items in greater detail in future articles in this series. I strongly encourage you to invest in yourself by developing the requisite skills:
- Fit the chipbreaker to the blade as lovey dovey as two newlyweds and so there is no gap between the cutting blade and extreme edge of the chipbreaker. This is not difficult to achieve, but the fit must be nearly perfect to prevent naughty shavings from wiggling between the blade and chipbreaker, because if they do get jammed, back-pressure will increase and the finished surface will look like poached crap on toast. We will discuss this more in the next post in this series;
- Fit the chipbreaker to both the plane’s body and retention rod so the chipbreaker will remain in-place;
- Grind a 70˚~80˚ striking bevel at the cutting edge of the chipbreaker to effectively buckle shavings. It doesn’t need to be a perfect bevel, and if it is rounded, that’s OK too. Yes, I know this seems ridiculously steep; If you don’t like it by all means experiment until your little pink heart sings, but after you’ve wasted a few months on hit-and-miss research, please remember that YMHOS toldjahso;
- Polish the striking bevel to reduce friction and prevent wood sap from building up on it too quickly. Re-polish it as necessary. If you pay attention to the condition of this abrupt bevel you will notice that it may actually become pitted from the heat and friction of the wood shavings, especially when planing wood containing hardish minerals. Total neglect will harm efficiency;
- Clean accumulated wood sap from the striking face regularly and oil it occasionally with your oilpot to reduce friction;
- If shavings tend to become stuck in the mouth, check to see that the chipbreaker is not so thick as to obstruct their smooth passage. If necessary, grind the chipbreaker thinner near the mouth and polish it to improve the flow of shavings;
- When you deem the chipbreaker to be necessary, install it as close as practical to the cutting edge. The ideal distance will depend on your plane, the wood you are cutting, and the depth of cut, but 0.5~0.8mm is usually a good place to start. I highly recommend you actively experiment to find the best distance. With practice it will become second nature. While it is not applicable to Japanese handplanes, Rhett Fulkerson of Nice Planes in Frankfort, Ky., has an intelligent technique for systematically setting chipbreakers and cap irons I find useful. LAP has an article about it here.
Conclusions
The chip breaker has been around a long time only because it consistently works.
In Japan, where the single-blade plane was the standard for hundreds of years, with the shift from riven lumber to more economical sawn lumber, the chipbreaker was added to the handplane, perhaps 150+ years ago, and remains in-use even today, solely because it consistently works.
The chip breaker won’t solve all your tearout problems, but it will definitely help on condition that you set it up and maintain it properly. It isn’t difficult and the results of doing so set the professional apart from the amateur.
In the next post in this swashbuckling tale of bare-chested Scottish warriors riding feather-footed war horses over the highlands to rescue buxom lassies clad in flowing gowns from evil leering Lords, we will describe in detail how to setup and maintain the awesome chip breaker. Don’t forget your kilt and claymore!
YMHOS
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