||[Jul. 20th, 2004|05:05 pm]
Was tired last night, kept trying to fall asleep on the way home, which is bad when you're driving.|
Instead of playing with the power equipment, I kept myself awake putting a new platen on the big grinder.
Which, I guess, is playing with the power equipment, but involves less chance of accidentally hurting myself.
Anyway, up until now I've been using a graphite-impregnated canvas fabric to line the platen, which provides a low-friction yet durable surfact to grind on. The problem is that the canvas wears away, resulting in a non-flat surface, and can wear away to nothing, resulting in a damaged, and no-longer-flat platen. A recent solution that's becoming popular among knifemakers is to use a highly-wear-resistant ceramic for the platen. Glass is also used, but runs the danger of heat or stress fractures at speed, resulting in fragments of glass moving at high velocity. This is generally a bad idea. The ceramic runs cool, is wear resistant to an apparently astounding degree, and in theory should last a very long time. We'll see.
At a knife show earlier this year I picked up a 2" x 9" x 1/4" hunk of this ceramic. It looks like honey-colored glass, but is heavier and certainly more expensive. The edges were quite square, so I beveled the leading and trailing edges to keep them from stripping the joint material from the belts. To bevel, I used a x100 (about 220 grit) Norax belt. It took quite a long time of grinding to put a 1/8" radius on the leading edge -- this stuff is tough.
To strip off the existing graphite canvas, I heated the metal platen with a heat gun until the adhesive had softened -- I use 3M standard spray adhesive, works fine for the graphite. It comes off with heat, but usually leaves a gummy residue. Fortunately, it turns out to be soluable in lacquer thinner.
Since I wasn't confident the spray adhesive would work as well on the ceramic, I decided to go with JB weld, a 2 part epoxy-like substance. A few minutes of mixing, some back and forth to ensure good contact, and into the vise.
Tomorrow, I'll see if it worked.