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Mekugi 目釘 (bamboo peg) replacement.

A traditional nihonto (Japanese made sword) is held together with a single small bamboo peg called a mekugi.  They are not riveted, glued, or screwed together.  A samurai staked his life on that one small peg.  Two or three poorly done mekugi are not as good as a single properly done one.  It is our opinion that mekugi on most production katana (including the ones we sell) should be replaced.  We do offer mekugi replacement, but you can do it yourself.

Removal and Inspection

Mekugi pins should be removed and inspected often.  You should not wait for the mekugi to fail or you might be in for a nasty surprise.  Swinging your katana might result in a three foot razor sharp projectile flying across the room.  The standard tool for removing the mekugi is a Mekuginuki.  This small brass hammer is made especially for the task.  A small pin unscrews from the top of the hammer.  This pin is used with the hammer to drive the mekugi out of the tsuka (handle).  Most mekugi can only be removed in one direction.  Some non-traditional katana are made with a straight mekugi instead of a wedge.  The ends of the mekugi may be under the tsuka ito (handle wrap) and the tsuka ito must be shifted slightly to remove the pin.  A brass hammer or wooden mallet and a punch can also be used.

The mekugi should not be dented, bend, or show any damage.  It should be replaced immediately if it does show any sign of damage.  A rattling tsuba may be a sign that the mekugi need replacement and should be inspected.  An improperly shaped mekugi ana (peg hole) can cause mekugi damage and should be corrected.  The mekugi should not need excessive force to be removed or reinserted.  This is a sign that the blade is not fully seated in the tsuka (handle) or the mekugi ana (peg hole) is not properly shaped.

Selecting the Proper Material

Chopsticks are not the proper material for mekugi!  There are many varieties of bamboo that are very soft and not usable.  Good mekugi are made of a special aged and smoked bamboo called susudake すす竹 .  Old shinai (bamboo training swords used for kendo) can also be used.  The mekugi should be carved from the outer part of the bamboo with the tightest grain.  This is the hardest part of the bamboo.  Wood is not a good substitute for bamboo.  Wood mekugi snap easier than bamboo which tends to deforms.  Water buffalo mekugi are for shirasaya (holding scabbards) and are purely decorative.

Orientation - Which end is up?

Everyone's first reaction is that the big end is up.  Mekugi are carved from the outer part of the bamboo which has smaller pores.  If you look at the end of a mekugi you should be able to see that the pores are denser and darker on one side.  That is the top side of the mekugi.  This side of the mekugi should be place opposite the blade towards the kashira (end cap).  The puts the strongest part of the mekugi where it is needed most.

Deburring the Mekugi Ana (peg hole)

The tsuka (handles) on many production katana are very difficult to removed.  This is due to the fact that the mekugi ana (peg holes) in the nakago (tang) were drilled with the tsuka already on the katana.  The tsuka is often never removed after that.  Often there are metal shavings in the tsuka from this drilling.  The drill leaves a large bur on the nakago that keeps make the tsuka hard to remove.  This bur is not the proper way the keep the tsuka attached and the sharp edges of the mekugi ana can easily damage the mekugi.  The mekugi ana should be deburred using a countersink or file.

Reshaping the Mekugi Ana (peg hole)

There are three types of mekugi ana problems common to production swords.  The straight hole (Last Legend), the small hole (MartialArtSwords), and the staged hole (Paul Chen).  The straight hole is drilled with a single size drill without a taper.  A mekugi should be a wedge that tightens in the mekugi ana and not a pin.  The small hole is just too small for a proper mekugi.  The shape is correct but the mekugi ana needs to be enlarged.  The staged hole is created by drilling in from the different sides of the tsuka (handle) with two different sized drills.  When the drills meet in the nakago (tang) it creates a collar that the mekugi must be forced through. 

All these should be corrected to create a proper sized tapered mekugi ana.  This can be done with needle files, a tapered reamer (used for sizing holes in sheet metal), or a tapered drill (used for pre-drilling screw holes).  We recommend an 8 to 10 degree taper with the large opening slightly less than 1/4".  Be careful not damage the tsuka ito (handle wrap) which may need to be shifted out of the way.

Fitting the Mekugi

The mekugi needs to be shaped in a wedge with the same angle as the Mekugi ana (hole in handle and tang).  A block plane or carving knife can be used.  The bamboo should be carved so that it goes completely through the tsuka (handle) and fits snuggly in the mekugi ana.  It should be sanded before being trimmed.  The ends of the mekugi are marked while fitted in the tsuka.  The mekugi needs to be trimmed with a very fine saw and then sanded smooth.  You should leave the outer dense part of the bamboo on one side of the mekugi pin.  This should be fitted opposite the blade towards the kashira (end cap) of the tuska (handle).