|cracked my platen
||[Sep. 7th, 2009|08:04 pm]
http://boomer.homeport.org/~ayen/photos/cPlaten.jpg for the morbidly curious. Rambling below.While grinding the sword, I managed to crack the platen on the big grinder. |
It's a special wear-resistant ceramic, transparent but a tinted a yellowish brown slightly -- basically, it looks like glass. By using it as the backing you reduce friction, improve belt life, and most importantly its flat and will stay that way. I've used steel, which visibly wears in a single day's use; a graphite impregnated canvas that lasted an amazingly long time, but which was visibly not-flat after a few weeks, and this, which lasted years and until it cracked showed no signs of wear.
Because as delivered it has a very sharp edge, you quickly learn the difference between glass and this stuff as you grind in a bevel. And grind, and grind, and grind -- just to put a radius of a few mm on the leading edge took half an hour, and another half hour to get it polished up to an acceptable slickness. As per the instructions, I mounted it on the cleaned, flattened aluminum of the original platen using JB weld, as it's much more heat resistant than most common epoxys. That stuff definitely holds, even with three cracks, two longitudinal and one horizontal (see pic) none of the pieces are moving or loose. I could probably keep grinding on it, but I've already ordered a replacement, and I don't want bits of loose ceramic flying out and damaging the newly repaired contact wheel.
While searching for a replacement, I also found a 60 psi propane regulator with gauge, which is 30 more psi than my current setup, and some more wrought iron, this time from anchor chain. One link, 8.5 lbs. That's quite a chain. Add in one 2" x 12" ceramic platen, and I'm done.
While poking around trying to find someone who carries the platen, I came across another tool I've been drooling over at other peoples' shops, a rotary platen. http://www.beaumontmetalworks.com/rotaryplaten.html has as good an explanation, with photos, as any I could give. Since I have a Bader III, it just slides in. The rotary platen provides the ultimate low-friction, wear-resistant, self-cooling surface, and you can adjust the tension down for slack grinding and up for flat grinding, plus some handy radii and angled contact surfaces. It's not exactly cheap, but what the heck.
Oh, and in other news, I start over at IP-Engineering on the 16th.