giant Cypress

Japanese jointer plane sole configuration

I’ve had the great good fortune to be co-author with Bob Rozaieski on an article for the Arts and Mysteries column in the April 2011 issue of Popular Woodworking Magazine about Japanese and western planes, and the differences and surprising similarities between the two. I’ve received some questions about the setup of a long Japanese plane tuned for jointing a board (naga-dai kanna), as there are some sources that state that there are at least three touch points on the sole of the naga-dai kanna: the front, the front of the mouth, and the rear. For this sole setup, the two most important points are at the very front and rear of the body, and in the article I only reference those two points. Because of the main thrust of the article, and due to space issues, I didn’t elaborate on the touch point at the front of the mouth.

Here’s the setup for a smoothing plane, that we all know and love. Touch points at the front and in front of the mouth, with the blade sticking down a bit below the touch points. Keep in mind that for this and all of the other figures, the gaps are exaggerated for clarity, and all of the hollows are on the order of less than 0.01”, and that what looks like a rectangular hollow is really a very shallow curve.

Here’s the setup for a naga-dai kanna, as described by Toshio Odate in his book and many other places. Touch points at the front, in front of the mouth, and the rear all in a line, with the blade sticking down a bit just like in a smoothing plane.

Now, if there is a rear touch point that is in line with the front two touch points, and the blade sticks down a bit below the line, there’s really no way for the plane to cut and to have all three touch points hitting the wood at the same time, especially considering the mechanics of pulling a Japanese plane. The rear touch point wouldn’t touch because the shaving would have been cut away from the surface of the wood, and would hover above the board by the thickness of the shaving.

In fact, this would be the same situation as a plane with a perfectly flat sole at the level of the touch points, which would be the situation in a western plane. And with the mechanics of pulling a Japanese plane, since downward hand pressure is applied at the front of the plane throughout the stroke, the most important touch points would be the front and front-of-the-mouth touch points, making the rear touch point unimportant, and arguably unnecessary, except for maybe the last few inches of the end of the board, when the front end of the plane comes off.

The thing is, I don’t think Japanese woodworkers would have gone to the trouble of making the third, rear touch point if it didn’t have something to contribute. Otherwise, they would have just used the topography of a smoothing plane for truing up a board.

So I asked Odate about this at Woodworking in America in 2009, and showed him his book where he describes this. This is when he told me that for a naga-dai kanna, the blade is set so that the edge is in line with the front and rear touch points, and the front of the mouth touch point has a very slight relief about the thickness of a shaving, which is not in his book. I’ve tried to show this in this picture, but if it isn’t clear, the tip of the blade is in line with the front and rear touch points, and the touch point in front of the mouth is very slightly relieved.

This makes sense to me. For truing up a board, more length is better, whether you use a Japanese or western plane. By relieving the touch point in front of the mouth, you allow the rear touch point to do its job, and you’ve increased the reference surface of a Japanese plane to the entire length of the plane, instead of just relying on the length of the plane from the front to the front of the mouth. And I’m sure that Japanese woodworkers would not engage in activities that wouldn’t help their plane perform better (read: make a touch point at the rear of the plane) if adding this touch point didn’t help with truing a board. And physics dictates that extra length helps.

Again, the fact that the front of the mouth of the plane does not touch the wood to the same degree as the front and rear touch points might compromise the surface, but that is why you’ll follow this up with a smoothing plane. Likewise, a western try plane is not expected to leave a finish ready surface — that’s what a coffin smoother/infill/#4 is for.

Finally, I’ve tried this setup with an old standard length kanna. The rear touch point does seem to help with truing, and the plane takes slightly thicker shavings than a smoother, about 0.003-0.005”, just like I would expect a western jointer plane to do. It won’t take gossamer thin smoothing plane shavings, but that’s not its job. So there is some empirical evidence to support what Odate told me.

Still, technique is important, just like with western planes, and all the setup won’t help with bad technique. I approach truing the edge of a board with Japanese planes like Bob Rozaieski does with western planes: start taking shavings from the middle, working outwards, and then take full length passes until you get a continuous shaving. If you kept going at this point, you could get a convex surface, but this is true for western and Japanese planes alike.

Now, this is really not the main thrust of Bob’s and my article in Popular Woodworking, other than that for truing boards, Japanese woodworkers were trying to take full advantage of the length of their planes, and that for this purpose, longer is better, and that Japanese and western woodworkers both knew this, despite there being almost no overlap between those two woodworking worlds in the 18th century.

Update: Frank Vucolo pointed me to this article by Toshio Odate in American Woodworker from 1993, where he explains this in more detail.

Japanese plane set up - IV: Maintenance

After setting up a Japanese plane, it should be good to go for quite a while. But over time, there will be some upkeep that needs to be done as the plane is used.

Being made of wood, a Japanese plane will move over time with changes in humidity and temperature. One result of this is that the sole may change its shape so that the hollow and relieving may not be optimal any more. The sole may lose its conditioning with wear as well. Luckily, getting the sole back into shape is a fairly simple procedure. Simply recondition the sole in the same manner as was done initially, although this should be even less work than the first time around. Again, one common problem area is the part of the sole immediately behind the mouth. That is an area that I commonly check for potential problems. If that area of the sole is bulging down, scrape it back until it is no longer touching the board being planed.

A Japanese plane blade is tapered slightly along its length and width. As the blade is sharpened, it will get shorter, and it will eventually reach the point where the blade will not reach the mouth any more. If this happens, the bed of the plane should be refitted just as was done with the initial setup. Scraping away the bed will lower it, allowing the blade to drop down further. Again, this should be even less work than the first time around.

If you examine the bodies of well used Japanese planes, lengthwise splits can often be seen running near the sides of the mouth. This is from the taper of the blade along the width, either from shrinkage of the body or from the blade shortening with use and sharpening, requiring more force to bring the edge of the blade down to the mouth. Much like the refitting of the blade by scraping the bed of the plane, the sides of the side grooves of the plane body will need to be pared to accommodate this as well, and the procedure is the same as the initial setup. The top of the groove should remain untouched, and usually only 1/16” or less of total lateral movement should be needed.

Finally, it is good to keep in mind that if the body of the plane gets to the point where it really can’t be rehabbed any more, that is an expected outcome. Toshio Odate has said that each plane blade should go through three plane bodies before it is completely used up.

Japanese plane set up - III: Final tweaks

After fitting the blade and setting up the sole, there are only a few things left to get this Japanese plane completely set up, mainly related to the mouth of the plane. The first thing to do is to double check the relationship of the blade to the mouth and throat of the plane. The corners of the edge of the blade should sit just inside the throat. If the corners extend past the sides of the throat, shavings are likely to catch and clog at that point.

There are also a pair of shallow recesses to be cut at the sides of the mouth, which helps with the transition from the front of the mouth to the rear part of the plane. Using a chisel, make a shallow cut down even with the front of the mouth, about 1/32”, and then pare a shallow ramp from the rear part of the plane to the bottom of the cut. This isn’t a necessity, and a plane will work well without these notches, but I’ve seen these notches on nicer Japanese smoothing planes.

How the corners of the blade sit inside the throat and how the notches should appear can be seen in this picture. The blade corner/throat relationship is better seen on the right side. This photo is from a different plane than the one I’ve been tuning up, mainly because the body of the plane I was working on already came with the side notches cut, and they were cut in backwards.

After tuning up these aspects of the mouth, set the blade and take a shaving. With luck, you’ll be making nice shavings at this point. With my plane, the shavings jammed up in the mouth like the Holland Tunnel at 5 PM on the Friday of a holiday weekend.

The throat of the plane right at the mouth is cut to be close to parallel to the top surface of the blade, or parallel to the bevel of the chipbreaker if the plane has one. If everything is perfect, the shaving will pass through uninhibited. In my shop, like Elvis, perfection has left the building, leading to the shaving jam. The easiest way to deal with this is to open up the top of the throat without altering the mouth, so that instead of being parallel, the gap opens up slightly from the mouth to the top of the throat.

I am fairly sure this is not traditional, but I used a mill file for this task. With care, chisels can be used for this task as well, of course.

In filing the throat, I’ve angled the file so that it makes contact with the top of the throat of the plane, but doesn’t touch the mouth at the sole at all. It doesn’t take much to accomplish this task. I only needed a few passes with the file to open up the top of the throat, and the shavings had no problems passing through the plane after that.

The other most likely thing to go wrong at this stage is that when the blade is seated, a downward bulge could form in the sole immediately behind the mouth, which will interfere with the action of the plane. If there are still problems with the plane after addressing the throat, double check that part of the sole and scrape it down some more, if needed.

Finally, put a small chamfer along the sides of the bottom of the plane, and another on the back of the plane where it is hit with a mallet to back the blade out. Check the sides of the plane to make sure that they are still square with the sole of the plane. The very ends of the soles should be square-cornered, which pushes dust out of the way of the plane as it is pulled along the board. An extremely well set up Japanese plane can take a shaving so thin that dust trapped under the contact points of the sole can affect the shaving.

I grabbed a piece of scrap wood to test the plane out. Of course, to make things hard on myself, the first piece of wood I found was a short length of quartersawn white oak. Here’s the obligatory planing money shot.

Not bad, if I do say so myself. I was able to get nice shavings off of scrap pieces of cherry, maple, and pine as well.

Altogether, setting up a Japanese plane is a pretty straightforward procedure. If I wasn’t stopping to take pictures along the way, I would guess that I could have had this plane up and running in about an hour, plus whatever time was needed to sharpen the blade. If you are interested in trying this out, get a cheap used Japanese plane from eBay, and try to get it into working order. These planes probably won’t produce sub-thou shavings, but the process of getting them to working shape is identical to setting up a brand new Japanese plane.

Japanese plane set up - II: Sole conditioning

After the blade has been fitted, the next thing to do is to condition the sole. I’ve used this schematic before, but this is the strategy for the setup of the sole for most Japanese planes. The only parts of the sole that touch the wood are a narrow area at the front of the plane and a narrow strip immediately in front of the mouth of the plane.

Getting to such a configuration is easier than one might expect. The first step is to ensure that the sole of the plane is flat and free of twist. Winding sticks are a great way to determine if the body of the plane has any twist, but they should be placed at the front of the plane and immediately in front of the mouth. If there is any twist, use your favorite method of flattening a board to eliminate it. The sole of the plane can be planed flat, of course, but alternate methods include using a scraper to selectively bring down the high spots, or using a piece of sandpaper on a flat reference surface, like a granite plate or a piece of glass.

The last method has the disadvantage of the possibility of embedding a piece of abrasive in the sole, but I’ve found that as long as a high enough grit of sandpaper is used, that issue seems to be more in the realm of theory. I’ve used 400 grit sandpaper for this step in the past, but for planes that I intend to use for really fine smoothing work, I’ll use a scraper, just in case.

Regardless of the method used, it’s important not to get too aggressive about flattening the bottom of the plane, due to the possibility of opening up the mouth if too much wood is removed, or bringing the sole out of square with the sides of the plane. Luckily, I really didn’t have to do too much to this plane to flatten the sole.

The next step is to mark the areas to scrape away. It’s pretty easy to use a square to mark lines at the front of the plane and in front of the mouth to delineate the areas to leave alone. The red shaded areas indicate the areas of the sole of the plane that need to be removed. I had initially marked those areas with pencil, but it didn’t photograph well. The pencil marks do help me keep track of where I’ve already scraped the sole of the plane.

Again, there are a variety of ways to scrape the sole. The traditional way is to use a Japanese sole conditioning plane, seen at top. This plane works almost identically to a scraper plane. My favorite method is to use a card scraper. A wide chisel can also be used.

The sole conditioning plane is used across the grain, as seen above. If I use a chisel or a card scraper, I tend to go along the grain, as seen below. This may or may not be traditional practice (definitely not in the case of a card scraper), but both methods also work well.

It’s also important to make sure that the entire area of the sole behind the mouth is relieved by a small bit. The easiest part to miss is the area immediately behind the mouth, especially since that area often bulges down a little bit as the blade is tapped in. Unfortunately, this is the area that will cause the most problems if it’s not completely relieved, just like a western plane.

Although this may seem like an awful lot of work, this goes much more quickly than one might expect. It took less than 10 minutes to scrape down the penciled in areas of the plane. There doesn’t need to be a huge amount of relief — 1/64” is more than enough. To check if the scraping process is complete, tap the blade into position, and place a straightedge with a notch to accommodate the blade edge across the sole, and hold the plane and straightedge up to a light. A thin line of light should be seen between the untouched areas of the sole at the front of the plane and in front of the mouth, and another line of light should be seen across the entire rear of the plane behind the mouth. If there is an area of contact, scrape that area some more.

This was hard to photograph, but the above picture should give an idea of what to expect. The straightedge makes contact with the front of the sole on the left, and immediately in front of the mouth on the right hand side of the semicircular notch. It looks like the straightedge touches the sole immediately behind the mouth to the left of the semicircular notch, but there really is a gap there. I think some dust got in the way.

Believe it or not, between fitting the blade and conditioning the sole, I’m almost completely done setting up this plane. There are just a few details left to go.

Japanese plane set up - I: fitting the blade

This is an interesting Japanese plane that my wife got for me for my birthday last year from Harrelson Stanley. It’s a plane made without a chipbreaker, and it’s interesting because of the materials used to make the plane. The body of the plane was made from beech by John Reed Fox, who is known for his use of Japanese tools in his work, and who was featured demonstrating Japanese planes on an episode of The Woodwright’s Shop.

The blade was made by Muh-Tsyr Yee, a Chinese-American blacksmith, who made the hard layer from O-1 steel. Between the O-1 steel in the blade and the beech used for the body of the plane, this may be as close to a domestically sourced Japanese plane as you can get.

The plane has been sitting in my shop for about a year, and I’m finally getting around to setting it up. Setting up a Japanese plane may seem a bit like a black art, but it’s really a pretty straightforward process, and you only need a minimal amount of tools to get this done.

The first step is to sharpen up the blade. Once that’s done, the next step is to fit the blade to the mortise in the body of the plane. Here’s the set up I use for this. From left to right, there’s a bottle of camellia oil, a piece of plywood with some scrap pieces of wood attached with screws to create a stop, a mill file and some chisels, one of which needs to be thin enough to get into the side grooves of the plane body.

The blade is held in place by the bed and the side grooves of the body of the plane. Although most Japanese planes also come with a chipbreaker and a pin, neither of those pieces are needed to keep the plane blade in position. A Japanese plane blade isn’t parallel on the front and back of the blade. Instead, it has a taper, giving it a wedge shape, and the side grooves of the body of the plane have a matching taper. Because of the wedge shape and the closeness of the fit of the body of the plane to the plane blade, the blade gets firmly locked into place once it’s properly seated.

To start, use the bottle of camellia oil to coat the flat area of the bevel side of the plane blade. Then put the blade into the body, and tap it in with a mallet until it stops. When I first started, the blade was a good 3/8” from reaching the mouth.

Hit the plane on the back of the body to back the blade out. The camellia oil will leave clear marks on the bed and side grooves representing where the plane blade makes contact with the body of the plane.

You don’t have to use camellia oil on the plane blade to mark the contact points. In the past I’ve scribbled on the back of the plane blade with a pencil, a Sharpie marker, a dry erase marker, and sprinkled some graphite powder on the plane blade for this step. I’ve heard of people blackening the back of the plane blade by holding it over a candle, but have not tried this myself. Any of these methods will work.

Now that the contact points are marked, remove the wood in those areas with your favorite implement of destruction. The areas that are fair game include the bed of the plane and the sides of the grooves. The upper surface of the groove should never be touched. I use a combination of a milled-tooth file and chisels. Alternatives include a regular file or a plane float.

I’ll remove enough wood from these areas to the point that the oil marks nearly disappear. If the blade is replaced after doing this, it will sit a bit further towards the mouth.

Lather. Rinse. Repeat.

Good music helps this task move along. I was listening to an old Hüsker Dü album. The goal is to get the edge of the blade to within about 1/8” of the mouth with just hand pressure. At this point, it should be pretty easy to tap the blade with a mallet to bring the edge to the level of the sole of the plane.

As I had mentioned, this is a pretty straight forward procedure. If you can fit a mortise and tenon joint, you can do this. The impulse is to go too slow in removing the wood. You certainly have to slow down as you get closer to the final fit, but at the beginning stages I was pretty aggressive with the file. It doesn’t take very many cycles of fit/file/refit to get a good feel for this process. It should take 30 minutes or less to completely finish this process.