Sword Polishing

[Ken Cox]

Friends with only a passing interest in edged-weapons have asked me about the relative importance of the sword polisher in the whole process of producing a finished art object or weapon.
I have responded to the effect that the artisan who forged the blade also brought it to a state of roughly usable shape using files and stones; however, the sword polisher actually refines the functional shape as well as creating an aesthetically meaningful surface on the steel.

Over the past year I have fashioned a short sword using files and abrasive cloth.
I have had great difficulty acheiving an aesthetically acceptable surface, meaning, I have not done so.
However, the repeated effort has refined the shape in a very positive manner, improving my original design beyond my expectations.

I have done my preliminary polishing prior to heat treatment, and this has raised the question in my mind of where polishing rightly falls in the whole process.

I would like to know the state of the traditional Japanese blade, in terms of shape and finish, when the polisher receives it.
How much of the final shape does the polisher create?
What further, if any, heat treatment occurs after polishing, and what polishing occurs subsequent to heat treatment?

This makes somewhat of a circular question, but I think one can catch the drift of it.

Finally, I wonder if my own polishing would go better if I had the blade heat treated.

Many thanks.

------------------
Luke 22:36, John 18:6-11, Freedom
If one takes care of the means, the end will take care of itself.

 

[Robert Marotz]

Okie, I assume we're dealing with Japanese-style blades. And as such, we're dealing with a reasonably quasi-japanese polish (abrasive paper and etch), as well as Japanese-style of heat treatment (yakiire, with the clay).

Even though I could vaguely explain the togi process, I'm by no means a traditonal polisher myself...so I will explain as well as I can speaking from the less traditional polish perspective. This also spares me from repeating the differences between the proper stones and paper.

ANYWAY, moving right along...if you want to polish before heat treatment, you're not going to have a lot of fun in heat treat. The clay needs to adhere to the surface, and smooth fine surfaces don't yield great adherence capabilities. Some makers like 80-120 grit finish. On the other hand, there are less traditional makers who forge or grind the curve in prior to heat treat and want to quench in a light oil so there's less potential warpage. I have heard accounts of these people going up to 400 grit belt finish before heat treat. Because the quench in this case does not modify curve much (if at all), the stresses endured by the clay are likely a lot less and don't need that extra grip.

From this point, you'd want to use the paper on a solid hard backing, either flat or slightly convex. If you are using papers, you can use anything from 40-80 grit to 120 grit. Clean up the shape as best you can and try to make sure the lines are relatively crisp (especially if you have shinogi [ridgeline] or yokote and any other physical lines to worry about). Make sure you have plenty of light from various directions and try to keep wobbles to an absolute minimum at this stage. At this stage you'll start setting the edge too. Gradually work your way from 8-200 grit up to 320 and 400 and 600 grit. Around 320 ad 400 you should have the shaping cleaned up to just about the best of your ability, and if you were thorough enough, you have probably chased down all the prior scratches. It takes a long time (sorry), but it gets a good result. If you want to etch at this point, feel free. Just do it very gently. Then work up from 600 to 800, 800 to 1000, 1000 to 1200, 1200 to 1500, and 1500 to 2000...You can skip stages, but it takes a bunch of extra work to chase down all the prior scratches. Once you're achieving higher than 600 grit, start using a lubricant for the paper (use Silicon Carbide paper). The lubricant can be an oil or it can be a cutting fluid. Just use it. This'll keep the material from mirror-polishing while you continue chasing down the lower-grit scratches. If you are happy with 2000, stay there. If you want to go higher, you can. I suggest 2500-4000 grit for the nicest finish.

However, the nicer the finish, the more fragile it becomes. If you want to carve a saya for it, make sure it's a soft wood, and that you have it carved and fitted before too far along in the polishing process, as you can easily scuff up the blade from the fitting. Once you are finished with the polish (whatever grit stage, 2000 is plenty for most), make sure you wipe down the blade well and wipe some oil over it, as the fresh surface will be prone to rust.

Phew...hope I covered it OK...am a bit tired...

Shinryû.