Saturday, September 5, 2015

Home-made Honing Disc. Getting tools sharp enough for moku hanga.

I don't know if the WorkSharp (TM), an American-made, motorized, disc sharpener for woodblock tools comes in a 220V version, but I was worried that the size and bulk made buying and bringing one to Italy in a suitcase impractical (especially since I was already 20kg overweight with blocks and paper).

But since TWO of our neighbors design shoes and handbags (another odd perk of living in Italy), we get the occasional leather remnant and I have a few pieces lying around. AND one of the cardboard pastry discs I use for my barens was way too big to use for a baren. AND I have 8 sets of Powergrip tools that I need to sharpen after my last moku hanga class for a workshop I'm giving this weekend.
So the odd juxtaposition of need, on-hand supplies, a model to use as a starting point, and the imminent need for 8 sets of sharpened tools got me motivated to try something I'd been thinking about.

 I took the cardboard disc and drilled a 8mm hole dead-center.
Then I glued the thin leather to one side with PVA glue (thinned a bit with water). To the other side I glued a 1500 grit wet sandpaper and pressed them both beneath some books overnight to dry.

Today, I loaded the leather side with honing compound (from McClains) and then threaded a long, 8mm bolt through the hole with washers on either side, and nuts to hold the disc tightly when it spins. I placed it into a handheld portable drill that I clamped to my table and by sitting just right (with safety glasses), I could hold the drill power switch with one hand to control the speed while looking  down the edge of the spinning honing disc and carefully place my U-gouges against it at just the right angle, turning them as I did so to finely hone the outside edge of the tool. By looking down the edge of the spinning disc I can hone on the top side with the leather wheel or hold the tool on the underside to lightly grind with the 1500 grit. I used a tightly rolled up piece of 1000grit sandpaper to remove any burr from the inside of the curve and looked at it with a 10X loop. Nice and polished. It took the hairs off the back of my arm with just a light touch. 
And just to be sure, the leftover piece of Okoume plywood that was tearing with the same tool yesterday, now cut cleanly and smoothly with no shredding.
We're in business.
Next, I tried the 1500 grit side of the disc on the Hangi Toh, I have to be careful not to get the tool hot or I'll lose the temper of the steel so I never held it for more than a few seconds at a time on the wheel and even the 1500grit takes metal off faster than I'd like so I do have to be careful.  But I put a new bevel on the Toh in less than a minute (on/off, on/off) and then buffed it on the leather side.

I made another disc (this time with a pressed-wood disc that came pre-drilled with a 8mm hole) it was for a decoupage clock face (3 Euro at the craft shop) and I glued a 600 grit and 1000 grit wet/dry sandpaper sheet to either side.
These will be used only for changing bevels and really dull tools.
The drill is held in a vice so I can power it with one hand while I can gaze down the spinning wheel and hold the tool against it. There is leather and honing compound on the top, a 1500 grit paper on the bottom half.

The stiffer disc was definitely an improvement though as there is no wobble so it's easier to keep the bevels even and true.  (And I think I'll try to convert my leather one to the stiffer disc as it's a little easier to control). But first:
Tomorrow I'm going to hone the 8 sets of Powergrip tools for my class.
While I do this regularly by hand (using waters stones of 1000/6000 grit) on my good knives but with this many tools, I think the honing disc will get them all sharp enough for the students in about a 1/2 hour.
More importantly, they'll be sharp enough that they'll carve the plywoods easily, and that will make the work easier for beginners.

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