The Iaido Journal  June 2002EJMAS Tips Jar


Copyright © Kathleen D. Fowler 2002. All rights reserved.

    This part of the series will continue to cover first aid repairs to the saya and koiguchi.  As most of these repairs are fairly involved, they will require not only time and patience, but in some cases fairly specialized equipment.

Tip #1 Fixing a Scratched Koiguchi

    Long, deep scratches inside of a koiguchi are one of the hazards of learning how to correctly draw and sheath a katana.  Fortunately, fixing them is almost as easy as making them.


Caution:  As with glue, wood putty can give off fumes which can damage the metal of a shinken (real katana); therefore, always seek professional help before attempting repairs.

Step 1: Clean the inside of the koiguchi thoroughly of any splinters, oil, or other foreign materials.

Step 2: Using a flat applicator (such as a popsicle stick), carefully smooth a small amount of wood putty into the cracks.

Step 3:  Allow the wood putty to dry completely.  This process usually takes at least twenty-four hours.

Step 4: File and sand down any rough surfaces on the putty, but be very careful not to damage the koiguchi.  Filing the wood itself will loosen the koiguchi's grip on the habaki and necessitate additional repairs (See Part II: Tip #4).

Step 5: Repeat steps 2-4 if necessary.

Step 6: Clean away any dust remaining from the filing.

Tip #2 Replacing Cracked or Worn Koiguchi Fittings

At the very end of the saya around the outside of the koiguchi is a little fitting that protects the soft wood during drawing and sheathing.  On expensive saya these fittings can be made of strong but pliable natural substances such as horn.  On mogito (practice blades), however, most fittings are made of plastic.  Through repeated use during practice these little plastic fittings inevitably become worn or cracked and need to be replaced.  The trick is in finding a suitable material from which to make the replacement.  A thick, pliable plastic which is strong but can be cut with utility scissors is the easiest choice.  Personally, I have had success with an old black coat hanger.  However, before deciding on any material test it to make sure that it does not chip or snap in half easily, or the replacement fitting itself will be weak.  The material should also be the approximate thickness of the original fitting and of a suitable color.


Step 1:  Remove the old fitting.  Using a utility knife, gently make an incision between the fitting and the lacquered surface of the outside of the saya tracing all the way around.  Be very careful not to make the incision too deep or the wood around which the fitting is placed may be damaged.  Gently pry the fitting straight off the end of the saya. Again, be very careful not to damage any of the wood.

Step 2:  Carefully clean away any bits of old glue which may be remaining on the wood on which the fitting rests.

Step 3:  Place the old fitting on the new material and trace around it both inside and out.

Step 4:  Using a utility knife make a hole in the teardrop-shaped space of the koiguchi opening.  Carefully carve away excess materials, testing it repeatedly by inserting it over the koiguchi.  Leave it slightly smaller than necessary.

Step 5:  Using a file and sandpaper smooth down the inner edge until it fits the saya perfectly.

Step 6:  Insert the new fitting on the koiguchi and trace around the outside of it again using the saya as the pattern.

Step 7:  Remove the new fitting and use utility scissors to cut the outside shape, leaving it slightly bigger than the tracing lines.

Step 8:  On the interior surfaces of the fitting where it will rest against the wood, use a utility knife to score cross-hatched lines in order to assure a tight bond between the two surfaces.  Do not score the surface of the wood itself.

Step 9:  Spread a thin coat of wood-glue around the outside of the koiguchi, and attach the fitting.

Step 10:  Allow the wood glue to dry completely (approximately twenty-four hours).

Step 11:  Using a wood file and sandpaper, shape the outside of the fitting until it is smooth and flush with the lacquered surface of the saya.  Be very careful not to scratch the lacquer.  In order to prevent accidental damage, a piece of tape can be wrapped around the lacquer where it joins the fitting.  Remove it after the filing process is complete.

Step 12:  To reinforce the joint, place a little tube lacquer onto a brush and dab it into the joint.  Allow it to dry at least a day.

Tip #3  Repairing a Saya Cracked at the Koiguchi

    Another common form of damage which can effect the koiguchi is a crack along the upper, convex edge which is usually the result of mistiming during a draw.  If left unrepaired this kind of crack can cause discomfort for the hand and snag on the obi.  In extreme cases it can continue to get longer until it threatens to split the saya in half.

First Aid

    For an emergency repair during practice, wrap black electrical or racket tape carefully around the saya over the entire length of the split. It is important, however, not to leave this tape on too long.  Over time the adhesive will come off and get on the hands, obi, and uwagi causing a sticky, black mess.

Permanent Repairs

    Repairing a cracked saya takes a lot more time and patience than most people want to put into it, especially since replacement saya for mogito are fairly inexpensive.  If for whatever reason a replacement saya is not an option, there are various ways of permanently repairing the problem. It's up to the individual to select the most suitable method.  Of course, remember to remove the sageo before beginning any repair.

Method I (Patch)

    Patching the crack with glue and fresh lacquer is the easiest, but also the weakest method of repairing a split saya.  Unless done extremely skillfully, it is also unsightly.


Step 1:  With the tape outline the cracked area.  The tape will protect the lacquer from accidentally being scratched during the next step, so make sure to place the tape as close to the damage as possible to avoid having to relacquer too large an area.

Step 2:  Using 80 grit sandpaper carefully remove the old lacquer from the cracked surface.  Be careful to remove only the lacquer, and do not damage the wood itself.  Use a wood file and fine grain sandpaper to complete the process.

Step 3:  Clean away all dust.

Step 4:  Spread a thin line of glue over the damaged area and work it into the crack using a finger.  Remove any glue on the outside surface of the wood.

Step 5:  Bind tightly with rubber bands.

Step 6:  Allow the glue to dry completely (approximately twenty-four hours).

Step 7:  Use a wood file and fine grain sandpaper to remove any rough surfaces, and again be sure that there is no glue on the outside surface of the saya.

Step 8:  Clean away any dust.

As discussed in  Part II: Tip #3, people who are allergic to poison oak, poison ivy, and sumac should not use natural lacquer as it contains the same toxin, urushiol.  They should instead use a synthetic lacquer which does not contain this substance.

Step 9:  On a clean palette place a little tube lacquer.  Add thinner if necessary to make it spreadable with a brush.

Step 10: Brush the lacquer evenly over the area being patched.

Step 11: Allow the lacquer to dry  (approximately twenty-four hours) between coats until  the desired thickness is achieved.  While the lacquer is drying, do not place it in direct sunlight or under fluorescent lamps because ultraviolet light will make the lacquer craze.  Also, keep in mind that although it seems strange, natural lacquer hardens best under slightly humid conditions, so do not store the repaired saya anywhere that is very dry.  After the final coat  allow the saya to dry thoroughly for a least a week or two.  Although it may appear to be dry, lacquer will continue to give off vapors of urushiol until it has completely hardened.  These vapors can enter the skin through the pores and cause allergic reactions.

Step 12:  If necessary to even out rough surfaces, a very fine grained sandpaper may be used.  Be careful, however.  Paper that is too coarse will scratch and dull the finish.

Step 13:  Remove the tape.

Method II (Bind)

    Another fairly simple method for repairing a cracked saya is to bind it with thin linen cord.  This technique is much stronger than a simple patch and allows for some artistic freedom in the style of wrapping.  The basics are as follows.


Step 1:  Determine how far down the crack runs.  If it is not too long, wrap the tape carefully around the saya about an inch or so past the kurigata.  The tape should be placed so that it lines up perfectly where the two ends meet.  Place tape over the kurigata as well to protect it.  If the crack extends too far past the kurigata, this is not the best repair method to use.

Step 2: Use 80 grit sandpaper to remove the old lacquer on the saya in the area between the koiguchi and the tape.  Be careful not to scratch the koiguchi fitting, the kurigata, or any area below the tape.  Also be careful not to damage the wood underneath the lacquer.  Use a wood file and fine grain sandpaper to finish the process.  Keep in mind the thickness of the lacquer that has been removed when choosing what gauge of  linen cord to use.  The cord should be a little thinner than the lacquer so that the repaired surface of the koiguchi is smooth.  A thick cord will bulge above the surface and may cause trouble during sayabiki.

Step 3:  Clean away all dust.

Step 4:  Spread  glue over the damaged area and work it into the crack using a finger.  Continue to spread glue over the entire exposed wooden surface.

Step 5:  Starting at the koiguchi, begin tightly wrapping the linen cord around the saya over the fresh glue.  The area around the kurigata is a little tricky and small triangles of exposed wood are inevitable.  Do not worry as these areas will later be covered by lacquer.  Stop wrapping at the tape line.  Do not worry about tying off the cord as it will be securely held in place by both the glue and the later coats of lacquer. Just make sure that it is lying flat and even.

Step 6:  Using rubber bands or other similar binding devices, securely fasten down the linen cords, especially the ends.

Step 7:  Allow to dry completely (approximately twenty-four hours).

Step 8:  On a clean palette place a small amount of tube lacquer (see previous warnings).  Add thinner if necessary to make it spreadable with a brush.

Step 9:  Apply lacquer evenly over the entire area between the koiguchi and the tape making sure to get it in between the linen cords.

Step 10:  Allow to dry  approximately twenty-four hours.

Step 11:  Apply as many additional coats as needed allowing each coat to dry before applying the next.  Keep in mind that each coast of lacquer increases the thickness of the area being repaired.  In order not to have to struggle with sayabiki, its a good idea to keep the surface level of the saya fairly even.  Therefore,  excessive coats of lacquer are not a good idea.

Step 12:  After applying the final coat of lacquer, allow the saya to dry for at least a week or two so that it may completely harden.

Step 13:  After it is dry, test the repaired surface with your hand for any areas that  are excessively rough.  Smooth these over with a fine grain sandpaper.

Step 14:  Completely clean away any dust, remove the tape, and buff.

Method III (Samegawa)

    Using samegawa is the strongest and the most aesthetically pleasing way of repairing a cracked saya.  It is also the most difficult, time consuming, and expensive method to use.  Do not attempt it unless you are sure that it is what you want.

Choosing Samegawa

    Although often translated as "sharkskin,"  "samegawa" actually refers to any type of marine hide having a nodular appearance.  The type most often used in saya repair is actually rayskin.  In choosing a hide keep in mind that the larger the nodules and the more tightly compact they are, the better the quality and the more expensive.  Prices usually start around ¥5,000.  Expect the hide to be a creamy color with transparent amber edges and very hard.  It will more than likely be slightly curled from the drying process and will have two small holes.  These holes are not defects, but are where the eyes used to be.

Preparing the Samegawa 
  • samegawa
  • large utility bowl
  • water
  • hide scraper or utility knife 
  • heavy duty utility scissors
  • pencil
  • ruler
  • newspaper
  • board
  • weight
  • chisel
  • hammer
  • rasp
Preparing the Saya 
  • flat wood file
  • fine grained sandpaper
  • masking or plumber's tape
  • 80 grit sandpaper
Applying the Samegawa
  • acid-free, water-based wood glue
  • tube lacquer
  • lacquer thinner
  • palette (or old plate)
  • brush
  • rubber straps, etc.
  • epoxy cement
  • lint-free rag

Step 1:  Pour water into the large utility bowl.  Submerge the whole samegawa, and allow it to soak until pliable.

Step 2:  While the hide is soaking, determine how long the crack is on the saya.  Wrap tape around the saya just a little past the end of the crack. The tape should be placed so that it lines up perfectly where the two ends meet.  Place the tape over the kurigata as well to protect it.

Step 3:  Use 80 grit sandpaper to remove the lacquer over the area to be repaired.  Be careful not to damage the wood, the koiguchi fitting, the kurigata, or any area past the tape.  Use a wood file and fine grain sandpaper to finish the process.

Step 4:  When the samegawa is pliable remove it from the water and place it between two newspapers.  Lay a board on top and weight it flat.  Then finish removing any lacquer from the area of the saya to be repaired.

Step 5:  When the wood around the crack is smooth and lacquer-free, wash it and allow it to dry in the shade.  Bright sunlight might make it dry too quickly and split the wood.

Step 6:  Next,  take the flat, but still pliable piece of samegawa and scrape the inside surface until it is of an even thickness and the color is no longer cream but more eggshell.  The nodules on the surface should be clearly visible from the back of the hide.  As the scraping process takes a long time, it may be necessary to resoak the hide to keep it pliable.

Step 7:  After scraping use a course sandpaper to smooth the inside of the hide.

Step 8:  Look carefully at the hide.  On one side of the surface are the two small eye holes.  On the other is the largest nodule.  Since that large nodule is used in making tsuka, it is wasteful to use it in saya repairs. Instead, use the part of the  hide between the eyes.  Wrap the hide around the saya so that the seam will be on the side opposite the kurigata. Determine the width then add a little extra to allow for shrinkage as the hide dries.  If in doubt, it is better to err on the side of being too big.  Do the same for the length.  Mark these measurements on the hide itself using a pencil and ruler.

Step 9:  Use heavy duty utility scissors to cut the samegawa.  Again make sure to allow a little extra for shrinkage and to compensate for the difficulty of cutting a straight line through the nodules.

Step 10:  Very precisely mark the hole for the kurigata again keeping in mind shrinkage.  Then cut using a hammer and flat chisel.

Step 11:  Wrap the hide around the saya slipping the hole over the kurigata.  Double check the size then remove and allow the hide to dry almost completely.

Step 12:  Smooth and bevel the edges of the hide with a rasp.  Recheck the size and trim if necessary.

Step 13:  Apply glue over the damaged surface of the saya and work it into the crack with a finger.  Spread an even coat of glue over the entire surface of the exposed wood and the inside surface of the samegawa.

Step 14:  Apply the samegawa to the saya and work into place.  Wet it slightly with a tissue to make it pliable enough to manipulate.  Overlap just a little the edges of the hide that meet.

Step 15:  Securely bind the samegawa into place and allow it to dry completely (anywhere from twenty-four hours to a week).

Step 16:  Unbind the samegawa and check it.  If all went well, it has shrunk to the correct size during the drying process.  If not, hopefully it is too large and merely needs to be trimmed carefully to the correct size. If it is too small, then the crack will have to be filled with epoxy and lacquer and allowed to dry again.

Step 17:  If left the way it is naturally, the samegawa would be too rough on the hands and would interfere with the execution of sayabiki. Therefore, it is necessary to take a rasp and file down the nodules so that they are smooth and even.  Special care should be taken at both ends to make sure that the junctions are smooth and snag free.  Also, be careful not to damage the kurigata.

Step 18:  After the rough work is completed with the rasp,  continue to smooth down the samegawa with finer and finer grains of sandpaper.  Stop when it is evenly smooth to the touch.

Step 19:  Clean away all dust.

Step 20:  See warning it Part II: Tip #3 regarding use of natural lacquer. If any possibility of an allergic reaction exists, use synthetic lacquer that does not contain urushiol, instead.  The choice of color will depend on the color of the saya and on personal preference.

Step 21:  On a clean palette place a small amount of tube lacquer.  Add thinner until it is somewhat watery.

Step 22:  Using a brush, spread the lacquer over the entire surface of the samegawa and into all the joints of the repair.

Step 23:  Before the lacquer dries, wipe it with a lint-free rag.  This will cause the lacquer in the cracks to be dark while lightening the color of the nodules.  The more lacquer that is wiped away, the lighter the nodules.

Step 24:  Repeat with several coats.

Step 25:  Use a little bit thicker lacquer at the joints to insure a good seal.

Step 26:  Allow the lacquer to dry for at least a week or two.  Keep in mind that even though it may seem dry, it can still be giving off toxic vapors which can penetrate the pores of the skin causing allergic reactions just like those of poison ivy. These toxins are active until the lacquer completely hardens.

Step 27:  Check the surface for any rough places and sand them smooth using a very fine grain of sandpaper.  Bluff.

Tip #4  Kurigata

It has only happened to me once, and I am still not sure how they did it, but somehow an airline managed to pop the kurigata completely off my mogito while it was still packed inside its protective case.  Fortunately, this kind of problem is easy to fix using a little sokui  (Part I: Tip # 3 ) or acid-free, water-based wood glue.  Do not use anything too strong as it may later become necessary to to remove the kurigata to make repairs.  Just spread a little glue inside the joint where the kurigata fits and slip it back in.  Wait for it too dry completely, and it is as good as new.

Kathleen D. Fowler is a Lecturer in the Department of English, Kagoshima
Immaculate Heart College
TIJ June 2002