Caring for your high carbon steel katana
Cleaning and oiling
Clean your blade after each use or about every 2-6 weeks if in storage, or if you live in a high humidity climate. Wipe the old oil off of the blade with a piece of flannel cloth, rice paper or paper towel. Clean blade with isopropyl alcohol or glass cleaner and wipe dry with cloth. Apply fresh oil with a clean cloth in a very light coat. If the oil beads, you’ve applied too much.
Mekugi should be checked for damage or loose fit before each use. If they are loose or damaged, replace them with a new set. Make sure you use properly smoked/cured bamboo and not light colored or “chopstick bamboo”. Delrin can be used as a substitute.
Maintaining the koiguchi
The koiguchi or mouth of the saya should fit snugly but too tightly. This is something you will need to maintain throughout the life of the sword, more or less often depending on usage or climate. To make the fit tighter, glue narrow strips of very thin wood to the inside of the top or bottom of the saya koiguchi. Add more, one layer at a time until desired fit is achieved, let dry and check fit in between layers.
To make the fit looser, use a small file to slowly remove material from the same areas until desired fit is achieved. Do not use sandpaper, as the grains could fall into the opening and scratch your blade.
Honing the edge
You can use a strop and green jeweler’s rouge to keep the edge of your blade razor sharp. If your edge becomes damaged, you may need to use a whetstone to repair and re-sharpen it.
You don’t need to disassemble the katana unless you are adding new fittings or if water/fluids seep under the habaki. Remove mekugi (both if there are two) with a removal tool, grip the tsuka with your thumb pushed up under the tsuba. Make a fist to apply pressure to the tsuba, raising the nakago out of the tsuka core. If it does not loosen with pressure, place a small wood block on top of the seppa and up against the habaki and while holding in place, gently tap the top with a rawhide mallet until loose enough to remove with the above method.
Always make sure to pay attention when maintaining your sword, it’s extremely sharp and can cause serious injuries.