Japanese Handplanes Part 2 : Blade Adjustment

I warn you, if you bore me, I shall take my revenge.

J.R.R. Tolkein

Your most humble and obedient servant has received many requests over the years for explanations about how to setup, adjust, maintain and use Japanese planes. It’s a big subject, enough to fill volumes and volumes, and an important one to woodworkers, but I will try to explain in enough generality that new guys can follow, but with enough detail that professionals may glean something useful.

In this series we will discuss how to adjust a Japanese plane so it works well, how to tune it to increase performance, how to treat the body to reduce warpage and keep it looking good, how to deal with normal wear and tear, how to periodically tap out and dress the ura during sharpening, and of course how to use a Japanese plane.

This last subject is extremely simple but one many amateur users of Japanese planes and most users overseas get wrong. It happens so frequently that I am confident the improvement in Beloved Customer’s personal performance with Japanese planes will improve dramatically from this last subject alone.

The problem with Japanese planes is that, while they are simple tools, they are actually more sophisticated than appearances suggests. Dealing with these subtle details without properly understanding them leaves many as confused as a ball of yarn among a dozen big-eyed kittens, so to avoid having too many strands running all over the place, let’s start with the basics, namely how to adjust them. For purposes of this discussion, we will assume our plane is in good fettle to begin with.

Preparing the Body

Although this is not an issue in the case of the planes C&S Tools purveys, Beloved Customer will want to inspect their plane, and perhaps make a few modifications to the body before playing with the blade too much.

Striking Chamfer

When removing the blade or reducing the cutting edge’s projection through the mouth, we need to strike the body on the 90˚ intersection between the flat end of the plane’s body and its top surface. Accordingly we need to cut a chamfer at this location to prevent damage to the body. How wide? 3~5mm is a good range. What angle? Cut the striking chamfer approximately square (90˚) to the long axis of the blade.

While you are at it, cut off the corners formed at the right and left sides of this chamfer.

This is a one-time operation.

Sole Chamfers

You also need to cut chamfers on the two edges at the right and left sides (long direction) of your plane’s sole. These chamfers have two purposes. First, to prevent the edges of the sole from chipping. Second, to make a small gap for your fingers to grip when lifting up the plane.

As the sole wears, Beloved Customers will need to be refresh the chamfers at the sole from time to time, so further explanation is necessary.

Some people like big honkin 45˚ chamfers at these locations. Your humble servant has even seen country bumpkins cut these wide chamfers and then carve unsightly grooves resembling a shark’s grin leading from the sides of the mouth to these chamfers for shavings to escape into. Codswallop!

Why is this a problem, you ask? Because the thinnest, weakest portion of any wooden plane’s body is the sidewalls right at the mouth. This is also where most warpage originates, so please don’t weaken it more than is absolutely necessary by cutting unnecessarily-wide chamfers.

In addition, wood removed from the sole by cutting overly-large chamfers reduces the bearing area of wood on the surface being planed accelerating wear on the sole. Keep these chamfers narrow at 2~4mm and a max angle measured from the sole of 25~29˚ More than this is unnecessary and possibly harmful.

A chamfer is not necessary at the trailing end of the sole so long as you have the self control to not strike the sole with your mallet.

Do not cut a chamfer at the leading edge of the sole as it will guide sawdust and shavings between the sole and the surface you are planing. Pas bien.

Top Chamfers

Apply a small chamfer on the front and side edges of the top surface, just enough to prevent chipping. 45˚ chamfers are fine, but a roundover (bozumen 坊主面 which translates to “Priest’s edge,” probably in reference to the bald head of Buddhist priests in Japan) is a friendlier, more elegant edge treatment, IMHO. Your choice.

Hammer or Mallet

In order to use a plane of any kind, one must remove the blade to sharpen it, and then re-install the blade and adjust its projection from the body’s mouth to produce a wood shaving of the desired thickness.

Like most wooden-bodied planes, one adjusts a Japanese plane by striking it with a hammer or mallet. To drive the blade further into the wooden body (called a “dai” 台 in Japanese) when installing the blade or when increasing the depth of cut, one taps the head of the blade down into the wooden body. Pretty straightforward. But like most things in life, there are both clever and stupid ways to get even simple jobs done. Let’s consider some of the clever ones, shall we?

You can use either a metallic hammer or a mallet made of wood, plastic or even rawhide to tap the blade or dai during these operations. They all work just fine, but there are long-term consequences to this selection you need to be aware of.

In Japan a steel hammer is traditionally used by carpenters to adjust planes. Without a doubt it’s convenient and effective, but there are some serious downsides to using a steel hammer you may not realize. Those include:

  1. A steel hammer always mushrooms the blade’s head, without exception;
  2. A steel hammer always dings the blade’s pretty face when adjusting the chipbreaker, and most critically;
  3. After many strikes, the high impact forces of steel hammers impart will often crack and even split the wooden body (dai). Ouch!

A deformed and ugly blade may not be a tragedy, but a split body is an expensive and time-wasting catastrophe, especially if you are a professional that needs his planes to keep cutting.

What did this brightly-polished plane blade do to deserve such barbaric abuse?
All the worst consequences of using a steel hammer on a plane are condensed in this one photo. Notice the mushroomed head of the plane which the owner has probably already ground down several times. We can’t see the blade’s face, but notice how the chipbreaker’s face is all dinged up. And I guarantee you the blade is even more damaged. And of course, the split dai. Tragic! What did this poor innocent little plane do to deserve such barbaric treatment?! And how much of this plane’s useful life did the owner waste?

There may be Beloved Customers who will say: “But I’ve seen Japanese craftsmen using steel hammers to adjust their planes, so it can’t be wrong.” The first part of this observation may be true, but the last bit isn’t. The undeniable truth is that steel hammers have created many ugly, dinged, bent, and mushroomed blades, as well cracked and splintered many dai, entirely unnecessarily. Some carpenters are especially abusive of their poor planes, sorry to say, but not all Japanese craftsmen are so inured to the suffering of their tools.

C&S Tool’s planes don’t deserve such violent abuse, so we recommend Beloved Customers use a wooden mallet to adjust them. Without exception. A plastic or rawhide mallet with a wooden handle will work just as well.

Removing the Blade and Chipbreaker

Both the blade and chipbreaker are removed by tapping the chamfered corner of the block behind the blade with a mallet. We discussed this chamfer above.

It is of course possible to loosen the blade by tapping flat on the flat tail end of the block, but there is a risk of striking the bottom edge and deforming or even chipping the sole. Best avoided altogether.

The physics work best when the mallet impacts are applied in a direction more or less parallel with the blade’s long axis.

The chipbreaker (uragane) must be removed before the blade, but you need to be careful to prevent two unfortunate things from occurring during this process. The first thing to avoid is the chipbreaker jumping out of the block uncontrolled providing Murphy the opportunity for gleeful mischief.

The second thing to avoid is the blade backing out of the body further/faster than the chipbreaker causing the chipbreaker to ride over the blade’s extreme cutting edge dulling it. This point is one newbies often overlook until they wonder why the pretty cutting edge they just sharpened is dinged even before they begin cutting.

How does one keep blade and chipbreaker under control? Your humble servant recommends pressing a forefinger onto the chipbreaker as shown the photo below and applying pressure upwards when removing it to encourage the chipbreaker to shift upwards in a controlled manner. Do the same on the face of the blade when its turn comes.

When removing the chipbreaker, apply pressure towards the blade and upwards with your index finger to monitor its movement and help maintain control. It is critical that the chipbreaker moves upward faster the than the blade to prevent the chipbreaker from contacting the sharp cutting edge dinging it.
While applying upward pressure with the index finger on the chipbreaker, tap the chamfer behind the blade to cause the chipbreaker to move up and out of the body’s mouth. BTW, please make it a habit to not strike the center of the chamfer, but instead alternate strikes between the right and left sides of the chamfer to ensure the body will provide long service.

Once the chipbreaker is loose, remove it and go back to tapping the body to loosen the blade further. Continue to apply light pressure to the blade’s face to better monitor the blade’s movement, and to prevent it from jumping out of the body.

The plane used for this example is an extra-wide 80mm finish plane with a blade forged by Yokosaka Masato. The oasaebo steel rod which retains the chipbreaker in-use can be seen tightly installed across the mouth. This is typically never removed over the life of the plane. In the center are the blade and the chipbreaker (uragane). A very nice blade hand-forged from Shirogami No.1 high-carbon steel. To the right is the mallet your humble servant uses for plane adjustments. Notice how the head of the blade is not mushroomed, its pretty face is free of the dings and divots, and the body is free of the dents, cracks and splits that often result from using steel hammers.

Adjusting the Chipbreaker (Uragane)

The chipbreaker is a recent addition to the Japanese plane. In earlier centuries, they had only a single-blade. Unlike the Western Bailey-pattern planes that incorporate the chipbreaker into the linkage necessary to adjust the blade, hiraganna planes work just fine without the chipbreaker. Indeed the chipbreaker’s only role is to reduce tearout, so when tearout is not a concern, removing the chipbreaker will reduce the force necessary to motivate the plane and may even produce a smoother cut.

The chipbreaker of a new plane often needs to be fitted to the blade and body using files and stones, but that is a subject for a future article, so to keep things simple, so for now we will assume the chipbreaker is in good shape and is happily wedded and bedded to its blade.

Gentle Reader is no doubt wondering how to adjust the chipbreaker with the large head of a mallet. The answer is to use the butt of the handle as shown in the photo below. Just hold the mallet’s handle in a fist with the head upward and bring the handle’s butt down on the the chipbreaker. Easy as falling off a dog, as my dear departed father would say. The connection between the mallet’s head and handle must be quite solid, of course. These mallets are easily made.

Using this technique, your plane blades will look beautiful, and your dai will give many years of reliable service. And although they only have tiny mouths with just a single, shiny, silver tooth, if you look carefully you will can see their clever little smiles.

Using the end of the mallet’s handle to adjust the chipbreaker. Notice that, once again, the index finger is used to monitor the chipbreaker’s movement and to keep it under careful control. To ensure the chipbreaker will do its job, its edge should ultimately be adjusted to be in very close proximity to the cutting edge (>0.002″ (0.05mm). This distance will vary with your plane and the wood being cut, and will require experimentation and fiddling to get right, but with practice, this process will become automatic and intuitive. Be careful to prevent the chipbreaker passing over the cutting edge as this may dull the blade causing Beloved Customer to say undignified things and Murphy to howl with glee.

To remove or back-out the chipbreaker, one strikes the dai as if loosening the blade, but with a finger on the chipbreaker to keep it from dragging over and perhaps dulling the blade’s cutting edge.

When adjusting the chipbreaker, sometimes the blade will shift position too, so a back and forth adjustment of blade-chipbreaker-blade is sometimes necessary. The tighter the fit of the blade and chipbreaker in the body, the more fiddling is required, so craftsmen such as joiners, sashimonoshi and cabinetmakers that routinely make fine, precise cuts and sharpen frequently tend to prefer thinner blades that fit into the body with less force and are easier to adjust than do carpenters who perform less refined work.

We will delve into this aspect of handplane setup in our journey ass over teakettle down the rabbit hole in a future post.

Adjusting the Blade

In order to take a clean full-width cut, the blade must project from the mouth the appropriate amount, and evenly across its width. In other words, it must not project too far, nor too little, and one corner of the blade must not project more than the opposite corner.

To evaluate the blade’s projection through the plane’s mouth, hold the plane upside down to a light-colored uniform background and look along the plane’s sole. The correct projection will be a thin line of uniform height across the width of the sole. If one side of the blade is projecting more than the opposite side, the blade is either skewed in the body, or it is shaped skewed.

If the blade is skewed, tap the head to the right or left with the mallet. If, however, a few taps fail to make the projection uniform, the blade’s cutting edge must be reshaped.

Please be aware that continued lateral pounding on the blade will not improve the situation and may damage the wooden body.

Most planes allow a little bit of wiggle room for the blade, but sometimes, especially if the body shrinks in width due to reduced ambient humidity, the notches in the side of the mouth may need to be pared slightly deeper, or the blade ground narrower, to provide this right/left wiggle space. Be very careful, however, to avoid paring these grooves more than a thin shaving or two wider because, as mentioned above, removing wood at the grooves directly and irrevocably weakens the most tender point in the wooden body.

When looking down the sole to ascertain the blade’s projection, a black line will visible above the sole as in this photo. A light-colored, uniform background is helpful for this. In this case, two adjustments are necessary. The first problem is that the blade is projecting too far. This is easily resolved by tapping the chamfer behind the blade, something that, with practice, can be done while the plane is held upside-down in this position. The second problem that must be resolved is the skew evidenced by the blade’s projection being much greater on the left side of the photograph.
Adjusting a skewed blade by tapping the blade’s head laterally. If a few taps will not correct a skewed blade, it probably needs to be reshaped to correct a skew that developed during sharpening.
A much smaller, useful projection with just a tiny bit of residual skew that must be corrected. When taking extremely fine finish cuts, the ability to determine the blade’s projection sometime seems more clairvoyant than simply optical.

To test the projection of the blade, and ensure skew has been removed, hold a short, narrow piece of softwood such as pine or cedar in your hand and run it over the cutting edge, first on one side of the blade, then the opposite side, and finally the center, and observe the shavings (if any) produced. They will tell you the truth. Be careful not to shave your fingers unless they have become hairy (ツ).

Even experienced craftsmen betimes become gutted, gobsmacked, and guragura upon discovering their otherwise perfect plane blade has become skewed and is projecting too far on one side to be adjusted for a good cut without resharpening it. Of course, the culprit is almost always pernicious pixies, but a wise Beloved Customer (inconceivable that there could be any other kind) will be careful to follow Petruchio’s example and tame the skew. And don’t forget to use a hardened stainless steel straightedge to check the blade for square when sharpening.

Striking the Body of the Plane

Your humble servant does not want to seem repetitious, but just so there is no confusion, I feel compelled to review a point or two before we end this discussion.

When backing out or removing the blade, make it a habit to strike the chamfered edge of the dai behind the blade alternating between the right and left sides instead of dead-center.

Also, angle your strikes so they are more or less parallel to the long axis of the blade. With a little practice this will become second nature. The reason for this action is simply that it is both more effective and at the same time helps to keep the dai in one piece.

Please, never strike the flat tail end of the plane’s body flat-on, but only the chamfered top edge behind the blade. Too many people who strike the flat end of the tail get carried away and end up damaging the sole.

If you examine your plane you will notice that there is actually very little wood holding the plane’s body together in the mouth area. Indeed the only continuous wood is at the sides, and it is only as thick as the distance between the bottom of the blade grooves and the exterior sides of the body. Not a lot of meat.

If we strike the body’s tail in the center, the body, being relatively unsupported in this area, must flex creating stresses, sometimes enough to crack it, sometimes even enough to split it. This sort of damage is common, but almost entirely avoidable because, if we strike the right and left extremes of chamfered edge behind the blade, stresses will be carried through the stronger sides reducing the chances of cracking and/or splitting the tail. You can feel and even hear the difference if you pay attention.

If you don’t care how your plane looks, and prefer replacing or fixing their wooden bodies instead of using them, by all means scrupulously disregard this suggestion, in which case you might want to get some extra bubble wrap to keep yourself entertained while the bolt and epoxy repair to your plane’s broken body cures.

Damage to the body or blades of C&S Tool’s planes caused by the incorrect use of metal hammers will void the tool’s warranty.

Plane Storage

When you purchase a plane, the blade is already installed in the body, although the cutting edge is usually recessed inside the mouth to protect it. The first step, therefore, is to remove the blade and examine it.

If you live in a low humidity area such as Nevada or Arizona in the USA and purchase a plane from a part of the world with high-humidity at times, such as Japan, it is wise to remove the blade and set the plane aside for a few days to let the body become acclimatized, especially if you plan to use the plane in a space with central heating and cooling which may cause the wooden body to shrink in width.

If you plan to store your plane for several years in a dry climate, or in a space with central heating and cooling, we recommend you remove the blade and chipbreaker, oil them, wrap them in aluminum foil, and store the body and blades together but without being installed in the body to prevent the blades from restraining the body’s shrinkage causing it to crack. Just to be safe.

In the next post in this adventure we will discuss how to modify a Japanese plane’s body to make it easier to use.

And please remember the wise words of the Sage of Possum Lake: “Remember I’m pullin’ for ya–we’re all in this together.


The end view of an amazing nagadai plane body by Inomoto-san made from a piece of Japanese White Oak combining “Oimasa” grain orientation and the highly-desireable ripple grain. In oimasa orientation a high ratio of the dense, tough, light-colored medullary rays are intersecting the sole, making the sole wear slower. Using plain-sawn wood will direct even more of these rays to intersect the sole further reducing wear, but at the same time will increase the tendency of the sole to warp. On the other hand, orienting the annual rings vertically in a “quartersawn” configuration would maximize the body’s stability, but at the same time would cause the sole to wear quicker while making the body less resistant to cracking and splitting. The oimasa orientation shown in this photo is a compromise intended to reduce warping without reducing strength while improving the sole’s wear resistance. Ripple-grain white oak is not only more beautiful, it exposes more of the harder winter wood at the sole making it both more wear-resistant and more stable than ordinary white oak. A thing of beauty.

If you have questions or would like to learn more about our tools, please click the “Pricelist” link here or at the top of the page and use the “Contact Us” form located immediately below.

Please share your insights and comments with everyone in the form located further below labeled “Leave a Reply.” We aren’t evil Google, fascist facebook, or thuggish Twitter and so won’t sell, share, or profitably “misplace” your information. May my plane blade be forever skewed if I lie.

Other Posts in the Japanese Handplane Series:

9 thoughts on “Japanese Handplanes Part 2 : Blade Adjustment

  1. I guess due to a western wooden plane being thicker we can get away with using a steel hammer. I still dislike the hammer marks it leaves on the plane, but what else is one supposed to do when the plane was designed to be hit. If and when I decide to make a new plane I will insert some kind of a decorative nut. But I’d hate to move from the traditional look. I can’t believe I missed out on Part 1. I’ll read that tomorrow. For now it’s bedy bye time.


  2. Great post, looking forward to the rest of the series. Is there an extra zero or two in the chipbreaker set example? 0.005 mm is a very very fine set.


  3. On squaring the cutting edge: I recently picked up a used kanna to learn with. The dai is solid with a mouth that is square to the bottom and sides. I’ve noticed that the blade is a trapezoid from side to side. About 67 mm near the top and about 62-63 mm near its cutting edge. I assume that is one of the subtleties that help wedge the blade into the dai?

    But that complicates squaring the cutting edge to the dai since the angle between the blade edge and either side is somewhat more than 90 degrees. So to square the cutting edge I’ll need a bevel gauge rather than a 90 degree square.

    Am I looking at the situation correctly?

    I have other questions but you may address them so I’ll hold off for now.


    1. Gary: Excellent point. The blade should be tapered in thickness from head to cutting edge along it’s length to provide the necessary wedge effect. It is also tapered in width, as you observed, being narrowest at the cutting edge and wider towards the head.

      The back (opposite the ura) is concave from side to side over much of its length, at least on good planes, to reduce weight and to help keep the blade aligned. Without this concave grind the blade would tend to twist out of alignment easily. Accordingly, the bed is not flat, but curved. One of the first jobs of setting up a new plane is fitting the bed to the back.

      As I mentioned in the post, the Japanese plane appears simple, but there are subtle and important details that make a big difference.

      These details are not a problem when it comes to correcting a skewed cutting edge IMO, but the taper means a square is not an accurate tool for determining if the cutting edge is going to be skewed or not. A bevel gauge would work, I think, but it assumes the block is perfect and the blade is uniform, something that seldom happens. Therefore, we need a little bit of wiggle room inside the grooves to allow us to make small corrections for skew. This works because of the blade being tapered in width too, of course.

      I prefer to just observe the amount of skew and correct it if I can by tapping the blade’s head right or left. The next time I sharpen the blade, however, I apply more pressure to the side of the blade that projects too far because of the skew and correct it a little at a time.

      If the blade is skewed when new, some heavy grinding may be necessary to make the correction.

      The key is to pay attention and “tame the skew” instead of carelessly letting it get out of control, as most people do with their first Japanese plane. I know I did (ツ)



  4. Thanks, Stan. I used my bevel gauge to get close and gauge symmetry then eyeballed it when fitted as you suggested. One related question: use finger pressure when sharpening to add a slight camber to the cutting edge so the corners don’t dig in and leave ridges?


    1. Cool! I’ll have to give that a try.

      Re your question: You hit the nail on the head.

      When finish planing boards wider than the width of the blade, it is effective to have the right and left corners of the blade slightly curved so the corners disappear into the mouth and don’t leave tracks and ridges on the finished surface. In the case of finish planing boards narrower than the blade’s effective cutting width, leaving tracks and ridges isn’t likely (unless you’ve been imbibing the planing fluid(ツ)) so a perfectly straight blade works best.

      Since finish planing wide boards works best by taking extremely thin, translucent shavings, it doesn’t take much of a curvature. This is a very subtle thing, far from the wildly “cambered” blade some of the gurus of woodworking promote for all operations. Usually a bit of finger pressure on the blade’s corner will get the job of resharpening done. When modifying a straight blade for this purpose, it sometimes helps to hang all of blade but the corner being modified off the stone for a few strokes.

      This method works well for Western planes too. The wood can’t tell the difference so long as the blade is sharp.



  5. Sorry about previous “contact” requests, forgot the comment section was in a different location…

    I can’t help but wonder if you are a hobbyist pipe smoker with the many mythical (shroom smoking caterpillar), Lord of the Rings, and Tolkien references.

    Not sure about that culture in Japan; in the American nanny state, it’s relatively frowned upon and lumped together with rat poison cigarettes.

    I am trying my hand at growing organic tobacco this year for the first time, though to get it into a pipe will take a year minimum. I think it runs in my blood being part Cuban. I’d also like to make a pipe stand soon with my new tools, varnish currently drying on chisel handle. I tried a cigar the day I turned 18 and a few after but never pursued it as a hobby. As I heard someone else say, if curing and fermenting tobacco wasn’t so hard (am also a homebrewer, and shoyu maker, I’d distill if it was legal), the government would make it illegal and so they could tax the crap out of you.


    1. Kooky: No, I don’t smoke anything, but the culture of the pipe is part of the literature I love. I wonder how the tobacco plant made its way to The Shire… Regarding taxes, government is at heart a gang of thieves. We can’t live without them, but we must watch them like a hawk or the servant will become the master…. Oops, too late.


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