How to make a bokken
by Kim Taylor
Wood selection: You must balance weight, strength and crush resistance according to what you are going to use the wood for. Price, especially if you are making your own is not as crucial since you will pay more for a cheap "maple" bokuto from Taiwan than you would for that much ceylon ebony.
Weight is crucial especially for the Aikido types who tend to go up against sensei not having the faintest idea what he is going to do. If your bokuto (OK Boken... OK OK Bokken) is slower than his (due to massive weight) you often get clunked. I make sure my boken is lighter than sensei's if I can manage it. (Gifting him with a heavy one usually works).
Strength is related to the "absolute" strength of your wood, and to the "relative" strength of your bokuto compared to your partner's. A good Brazillan Blackwood bokuto will simply destroy a red oak bokuto within about three hits. Crush resistance is the ability of the wood to dent without the fibres breaking causing splintering.
You also need to worry about the grain pattern of the wood. No knots, and a smooth grain that doesn't run out half way down the blade. The grain must run down the blade (obvious) and also be lined up so that it runs from back to edge (not so obvious). THIS MEANS THAT BLOCKING WITH BOKUTO SHOULD BE DONE WITH THE EDGE not the shinogi as is being suggested in some of the mail here. (There are some thoughts on blocking like this from some senior Japanese sensei as well, I'll try to find the relevent item in the newsletter and post it soon). This is the reason ironwood is usually not good for bokuto, the grain usually goes all over hell and you're sure to get some that go the wrong way about 1/2 way down the blade.
North American Hardwoods:
Hard Maple: Good crush resistance, tight grain, good strength and weight for everyday practice.
White Oak: Often poor crush resistance due to porous grain, if a tight grained piece can be found, will often make an excellent bokuto. Red Oak, Pin Oak etc. are NOT suitable.
Hickory: My favourite, it often shows heartwood and outerwood of two different colours, one harder than the other. Hickory is slightly "shaggy" and so must be sanded fairly often. Excellent crush resistance and strength with fairly low weight. Probably the best all round North American wood for weapons.
White Ash: Usually a bit light, but strong. Open pores make it "crushable" like oak. A tight grained piece makes a good weapon for smaller students who can't safely use heavier bokuto.
I've used other woods such as cherry, elm, beach etc. but the suitability generally depends on the piece of wood more than the species.
Here are some of the woods I've used for bokuto.
Purpleheart: Deep red colour, nice straight grain, a little bit crushable but can be an excellent everyday bokuto if you want more weight.
Ebony, Makassar: Fairly strong, black with brown stripes, more suited for lone practice (suburi) than partner practice. Moderately heavy. Ebony, Ceylon: Black, VERY expensive and hard to find in suitable grain patterns (as if you could see the grain in some pieces) I've seen these bokuto literally explode on contact due to stress cracks inside the wood. Not recommended for use in partner practice.
Brazilian Blackheart (redheart): Was being imported as an ebony substitute, but not any longer. It would not glue to anything due to the resins in it, and it had a bad habit of dulling tools. This is the strongest wood I've ever seen, I weigh 230 pounds, my Tachi Uchi no Kurai (Iaido partner practice) weighs at least that much, and we use a pair of these to demonstate. Some of the kata require full stop blocks against a full strength strike. These things don't even dent. Interestingly, I once accidentially sliced a piece off one of them with my "dull" aluminum iaito.
Ipe: Another very hard wood. This one is a lighter brown that, with a good finish, shows rainbow coloured flecks that make it look like you are actually seeing into the wood. Not as heavy as blackheart (not much is). The sanding dust from this wood is green and turns blood red when you wash with soap. A small note here, there is such a thing as carpenter's cancer (nasal cancer) and these exotics with their resins are great for it. Some of these woods can cause an almost instant irritation so be careful.
Cocobolo: Deep red with black stripes and swirls. Grain tends to be screwy but it is so tight it doesn't matter. Heavy. Tools must be very sharp as the resins in this can literally bounce a spokeshave off of itself.
Kingwood: Very pretty, more for looks than for partners. Expensive.
Ziricote and Bokote: These are rosewoods, brown an black grain, the ziricote tends to be blacker and harder. It also produces a very irritating dust, I prefer working with bokote. Mainly for show but will stand light partner work. (Heavy if used against anything bought in the local martial arts store).
Lignum Vitae: The hardest wood around. LV is used in steamships as a bearing for the propeller shaft, not steel ball bearings but just a chunk of this stuff. I've never found a piece big enough to make a bokuto out of. Made a shoto though, even with a crack it would pound anything else to pieces. Slightly greenish wood.
Tulipwood: Not the North American wood that is like (is?) Poplar but the stuff that some company in England made sports car frames out of. Expensive, and hard to find a good piece. I've made a few canes out of this wood which is red and cream striped. Good properties.
I've probably tried a few more woods but can't remember them right now, if anyone wants to try another let me know and I'll tell you if I've tried it.
For a first try I'd recommend maple. It's a nice wood to work and can be found easily. Hickory is a bit more difficult to find since it isn't really a woodworker's wood. (More a tool maker's wood ie ax handles etc.) Poplar is showing up in some of the softwood lumberyards around here, it's a bit soft. If you're wondering about a new wood, try the thumbnail, rip and bend test. (Sounds painful? Let go of your thumbnail then.) 1. Press your thumbnail into the wood at a corner, does it crush easily. 2. Take a loose sliver at the end and rip it down, is it a long fibre or a short one? Does the fibre break easily (is it brittle) or does it bend? 3. Take a board and put one end on the floor, hold the other end. Look around and make sure nobody's in sight. Now lean on the board, if you hear it start to crack it's probably not very strong. If the wood passes all those tests, find a piece with good grain and start cutting.
About long fibres, I once made a bokuto out of a wood called Ramin. It had very long, strong straight fibres and seemed to have good crush resistance. The first time the student used it the damn thing split right down the long axis. I swear that wood has absolutely no cross connections at all. Don't use Ramin.
Parts of the bokuto
Here is a list of parts on the bokuto, they are the same as the names for the parts of a live blade.
Kissaki: the tip.
Mune: the back of the blade.
Monouchi: the cutting portion of the edge, the 1/3 closest to the kissaki.
Chu-o: the middle third of the blade.
Tsuba moto: the third of the blade closest the handle.
Tsuba: the guard, not present on most Aikido bokuto.
Tsuka: the handle.
Shinogi: the ridge between the mune and the edge.
Shinogi-ji: the flat plane between the mune and the shinogi
Jigane: the flat plane between the shinogi and the temper line (edge).
Ha: the edge
Tsuka gashira: strictly the pommel fitting, butt end of the bokuto.
Obtaining a bokuto
The wooden sword is usually made from oak, maple or hickory if it is to be used in partner practice. These woods have a high degree of strength and impact resistance. Maple and hickory are especially resistant to the splintering which may occur after repeated denting of the blade in the contact with another weapon. Other, more exotic woods, such as ebony, cocobolo or blackheart are sometimes used for their density, the greater weight more closely matching the metal katana. These woods are expensive and often contain flaws which make them less suitable to use in partner practice but ideal for individual training. While the weight of the bokuto may approach that of a katana, the balance is always different. The katana, due to its metal blade and wooden handle, has a balance point much further forward than that of a bokuto.
Specially shaped wooden swords called suburito are used to practice the individual cuts of a sword school. These weapons are designed to approximate the balance of a katana but are much different in shape and size. Often suburito of great weight are used to strengthen the arms and improve the posture.
Once a student has decided to study the bokuto the selection of a good weapon is of great importance. The suitability of a sword will determine to a large extent the ease with which a swordsman completes his practice. A student will own a bokuto for many years if it is chosen carefully and one should look for several characteristics when buying the weapon.
The shape and colour of the sword should be pleasing to the eye, the grip should feel smooth and free of stickiness which will cause blisters. The grip should also be large enough in the hand so that the fingers don't touch the palm. A badly sized handle can cause excessive cramping in the hands and a poor pattern of callous formation on the palm. The wood grain should be straight, with no knots and run from the handle to the tip. The growth rings should also run from the top of the sword to the edge. This pattern will give the strongest Bokuto possible. Look for a tight, closed grain which will resist denting. No warps or cracks should be seen. The wood should only be finished with tung oil or boiled linseed oil. Hard surface finishes such as varnish will cause the handle to be sticky. The weight of a Bokuto should be such as to allow the completion of a two hour practice which might include several thousand cuts. For this reason, students should consider beginning with a lighter sword and then moving to a heavier version when the arm and shoulder strength permits. A sword that is too heavy can cause muscle strain, and the slowness with which it must be moved can cause problems during partner practice.
Making a bokuto
With a few basic tools it is not hard to make a bokuto. The first consideration is which wood to use. The choice will depend on what style of sword is being made and whether or not it is to be used for partner practice. Once a source of suitable wood is found the actual piece must be chosen. Use a board that is about one inch thick and at least two inches wide for a bokuto. A suburito may require other dimensions. The grain must be straight and preferrably running along the wide dimension of the end of the board, rather than across it.
I'm going to describe how to use a lot of power tools to make your bokuto, you don't need all of these, so adjust the instructions according to what you have.
Much of the wood available these days is not fully dry. If it is practical, buy your wood and store it for several months to a year in conditions similar to your practice place. This will ensure that the wood is at a proper humidity level and any faults that are going to develop will do so before you start working.
The easiest way of laying out a pattern for the curve is to use a bokuto you have already decided you like. If you don't have a pattern then cut the board to about 41 inches long and at least two inches wide. Check the grain patterns and decide which end of the board is weakest, this is your handle. If the grain has a curve then the curve of the sword will follow it. Decide how far along the blade the bottom of the curve will be. For Bizen style blades the point of maximum curve is close to the handle, for other styles it is closer to the middle of the blade. Mark out a curve so that the bokuto is about one inch tall (from ha to mune). The top of the handle and the point will touch one side of the board. The point of maximum curve on the edge touches the other side if the board is 2" wide. Cut out this sword blank with a band saw or a sabre saw. I even used a 5 1/4 inch circular saw for a few blades when I had nothing else. The small blade will make this curve.
This is the time to decide what tip shape you desire, some sword styles leave the point blunt while others use a modified point. The commercial bokuto mimic the point of the katana. If you want a point cut the end at the angle preferred.
If your bokuto is going to taper toward the tip (it should to look good), and you have access to a jointer, mark the taper on the concave and convex sides and by using a series of longer and longer passes over the blades, create the taper on the sides of the blade. If you don't have a jointer you'll simply do this by hand when working on the shaping of the blade.
To carve out the shape some people prefer a wood rasp, some a plane. I prefer a combination of a spokeshave and a Stanley Surform depending on which wood I am using. I have a Workmate bench which is about the correct height for me to work on. Start with the blade section and do the handle last since the squared handle will allow you to keep the blade in the correct orientation while creating the long straight lines needed to produce a good looking bokuto.
Clamp the wood so that you can cut out the back ridge. For this you also need to have the blade clamped straight up and down. Hold the spokeshave at the chosen angle and use long smooth strokes to cut the shoulders. A 45 degree angle will make a round looking blade while an angle more toward vertical will create a thin blade. This is a matter of taste. When you have these shoulders cut to a straight pleasing line then you can start on the edge. Turn the blade over and work the curve into the bottom of the blade. A more rounded edge will create a heavier sword with a more resistant striking surface. A sharper edge, while weaker, will have a more pleasing shape. Make sure while you are working that the edge is lined up with the top of the blade. Clamping the squared handle will help with this. The edge will often wander as you cut so be careful. It is at this point that you determine the balance of the blade by how much you taper the blade toward the tip.
If you want to mimic the katana point use a Surform to cut a plane in from each side at the tip. If there is to be no point or a modified point then use the Surform to round off the edges of the tip and the base of the handle. Now is the time to even out any wavers in the lines along the back.
Clamp the blade carefully and cut out the handle. This is an important step since the handle is what you grip and it must agree with the curve of the blade. As a general rule the handle should be an oval shape with the long axis of the oval arranged so that you know where your blade edge is facing. In other words, the top and bottom of the oval must line up with the mune and ha.
If you have access to a fixed belt sander then use two hands to smooth off the wood. Your straight lines will become straighter at this point, and a lot of shaping can be done with a 36 grit belt. If the sander has a large flat bed you will have to create a padded "hump" on the bed with foam and masking tape so that the belt moves in a curve to fit the concave mune.
If you don't have a sander, you must work much more carefully with the hand tools unless you like blisters on your hands from the hand sanding. Use several grits of sandpaper to smooth the wood and close the pores. After sanding apply boiled linseed oil or Tung oil to finish it. Do not use surface finishes like varnish, urethane or danish wood oil. These will create a sticky surface that will give you blisters. An oil finish allows the wood to soak up the sweat on your hands while keeping the grain from lifting too much. If you use linseed oil make sure it is boiled, raw oil will never dry. I prefer tung oil.
If the blade feels good in your hands and is the right weight, the appearance is not important. This is a tool and it will soon be banged up so don't worry if it is not a museum piece.
The bokuto should be carried in a bag to protect it from sudden changes in temperature and humidity. The wood is not fully sealed by the oil finish so changes in the atmosphere may cause warping or checking. Never store the bokuto for a long period without support along the length, and keep it out of the sunlight. Treat it with the proper care and it will be useful for many years of hard service.