Hand Tools

Subject:
Theory vs. Practice
Response To:
Crystolon ()

David Weaver
The india stones have a harder binder and they are graded quickly by really hard tools. The fresh crystolon stones in an oil bath don't.

In practice, they just work better for grinding whereas the aluminum oxide stones settle in pretty quickly and are better at following them. The loose grit if SC goes all over the place (in an oil bath mostly in the oil) - I think that's why there's a huge surplus of barely used medium and fine older carborundum corp. SC stones.

If a crystolon stone is older and the binder is hard and doesn't release particles, then it's no good for this.

The other thing that SC does well vs. al-ox is if you have a high carbide steel (SGPS is an example that I learned in practice - it's grabby on an india stone - silicon carbide doesn't do that and just wastes it away like crazy. SGPS literally likes nothing other than silicon carbide and then loose abrasive on a soft backer All other abrasives (even diamond on cast) grip the carbides or something and what you're left with is a steel with little pocks taken out of it.

For sandpaper and lapping, what you say is true - neither paper is really great for hand lapping (the green and purples and blues make even less economic sense), but the cheapest red and white alumina do fairly well (and they're cheap, so you don't have to fret throwing them out and getting more fresh paper). Silicon carbide paper is graded almost instantly and it may be "sharp particles" left behind, but they're too small to be worthwhile.

The other variable here is wrought iron, mild steel or pure iron backing - the silicon carbide deals with it well. It's kind of rubbery on alumina - I think it likes a tumbling abrasive better for fast cutting so that it doesn't just get grooved.

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