Lapping on silicon carbide powder versus sandpaper

[now]

Are there any obvious benefits to lapping on silicon carbide powder instead of sandpaper, other than cost?

 

[Diemaker]

I find it works much better. The stones are flatter and more open so more aggressive, as well as loose abrasive works faster. Too bad it makes such a mess.

 

[Dangerously]

I read that it works differently than sandpaper, because the loose SiC abrasive rolls rather than just scrapes the stone. This is supposed to provide some benefit. Perhaps it doesn’t flatten the abrasive so fast.

I know that I’ve liked the results, and how easy it is to use SiC powder on a piece of glass for lapping my Norton crystolon.

 

[lex2006]

I agree the SIC seems to work better, only downside is the mess vs the sandpaper. I learned the hard way to use a piece of Float glass, not tempered glass.
Tempered is very rarely flat.

 

[eKretz]

I read that it works differently than sandpaper, because the loose SiC abrasive rolls rather than just scrapes the stone. This is supposed to provide some benefit. Perhaps it doesn’t flatten the abrasive so fast.

I know that I’ve liked the results, and how easy it is to use SiC powder on a piece of glass for lapping my Norton crystolon.

Yes it is a different mechanical process occurring. Sandpaper or abrasive sheets remove material by a mechanism called "2-body abrasion" while loose grit removes material by the mechanism called "3-body abrasion." In the former, the abrasive is dragged across the material being abraded. In the latter, the abrasive rolls and/or slides between two surfaces, abrading both.

 

[Spideyjg]

Loose SC on glass is really loud and eats into the glass over time.

 

[Diemaker]

The flat surface doesn't need to be glass, in fact glass is not that hard. It can be anything relatively hard and flat. Go dumpster diving behind a tile store and you will have a lifetime supply of flats. Or go into the store and ask if they have any granite tiles for cheap. Often they will have leftover tiles that don't match what they are now getting, stone is sold in lots that don't necessarily match each other. There are lots of flat surfaces that will work, just be open to look for them. One idea I haven't tried yet is a plastic cutting board.

 

[eKretz]

One I've wanted to try is tungsten carbide. Might keep flatter longer than anything else. Been thinking of making a lapping plate with some flat machine tool inserts brazed to a block of cast iron just to try it out. Definitely not for the average guy though, you'd need a surface grinder with a diamond wheel to flatten it out.