A katana's blade is an intricate piece of equipment and, when damaged, needs to be treated with expertise and great care. This doesn't mean, that anyone who has a working blade shouldn't try to do his or her own repairs to have the blade cut again. In most cases all that's needed are some basic skills, common sense, a steady hand, lots of patience and some basic and inexpensive tools to work with
Mono tempered blades are extremely difficult to work with as they are hard throughout. In comparison, differential tempered blades, besides their cutting edges, are softer and easier to work with. In any case, a steady hand is all that's needed with lots of patience and some pride in one's own workmanship. There is nothing more satisfying then having resuscitated and brought back to life a near dead blade.
Restoring a damaged cutting edge. By Hans Fricke
Three views of the damaged cutting edge
This katana, advertised as "battle-ready" for tameshigiri and "hard" target cutting failed miserably when used to cut through actual bone ...
Restoring a damaged cutting edge.
The blade's cutting edge I repaired had been chipped, bent and broken and the blade itself slightly warped; all in all some very serious damage and beyond most people's capability to repair.
Here are some basic steps that can, most of the time, restore a blade to its full glory again.
The blade in question had some deep (1.5 -2mm) dents stretching some 75 mm along its cutting edge and for this the edge had to be worked back for a total length of some 280 mm. Done this way,and after completion, the width reduction was hardly noticeable. Sections where the metal had bent or folded over (X) were not straightened out as this would have allowed the steel to break away again when under stress and therefore had been worked back and smoothened out with a stone instead.
Before re-sharpening could commence, pic. (a) shows how much the blade would have to be worked back to maintain a constant, but slightly reduced blade width. The most common error made is to just work on the damaged area only, thus creating unsightly and dangerous dips along the edge, pic. (b) .
Next I used the same stone (fine) for restoring the cutting edge after the edge had been taken down. It's important not to work into the profile or shinogi and to work both sides of the blade equally by counting the stone's passing over the surface. This will assure that the left and right blade profile is been maintained. Once the cutting edge and the blade's profile had been restored I moved into the next phase.
Here I used 800 and 1200 grit wet and dry respectively. I cut thumb size pieces, wet them with water, and with steady pressure of the thumb worked them up and down the blade smoothing out all marks left by the stone.
An important point to remember: To never use wet and dry paper on sharp and ragged edges as this can lead to serious injury to the thumb. All producing edges must be removed first with a stone .
During this phase I work in small increments along the blade (40-50 mm) and as each piece of wet and dry will only last for a minue or so, its a good idea to cut a lot of pieces before starting. To maintain the blade's profile I always do an equal number of polishes on each side and polish by applying steady pressure to the surface. After I have used two pieces of wet and dry I fold the blade over and repeat the same from the other side; repeating the same process over and over, till both surfaces are smooth and flawless.
All the while I check the sharpness of the blade by gently plugging the cutting edge with the side of the thumb like one would plug a guitar string, or cut paper and watch for the blade to either hesitate or stop. If that happens, I continue to work on those areas till the blade will cut without hesitation and is thus ready for its final hone. This I do with 1200 grit wet and dry, and by concentrating on the cutting edge only I gently polish back and forth (10-15 mm), all the while putting only light pressure on the edge itself. Once I'm satisfied that the blade cuts and looks well, it's then thoroughly cleaned, polished and oiled and ready again for an other workout.
Total time spent: 160 min.
Once the blade cuts and its surface is smooth again its time to clean up.
Maintenance kits are expensive and only needed for Japanese blades or other high quality katana.
Bright Shine keeps the blade spotless clean and in an emergency can even be used on a polished Japanese blade.
Soft tissue paper; I always carry it with me.
A thin film of Singer Oil is all that's required to keep a blade from rusting. Just a few drops on a soft cloth will do.
After having dried the blade, I clean and remove stains with Bright Shine.
... and cleaning the stone and sharpening steel with warm water using a tooth brush completes the job.
Cuts well ...
... and looks great again.
( 3 )
... and here is the culprit.
The reduction and re-shaping was done with a semi rounded diamond sharpening steel and a SPYDERCO 303MF Pocket Stone 1x5in medium/fine.
The damaged blade
Cleaning and maintenance
After Bright Shine has dried I remove film and metal dust with tissue paper...
... and repeat same by using new tissue paper till paper stays clean
I then clean cutting edge with tissue paper.
Finally I use an oil cloth to oil back and sides of blade...
... and finally use oil cloth to oil cutting edge.
Clean tools make easy work.
( 3 ) To clean a blade safely it's always wiped with a long steady movement from handle to tip.
© 2009 - SSJS, SEI DO KAN All rights reserved.
blade repair & maintenance hints