Oilstone Questions

[James Taglienti]

Good Morning.
I recently came into a stack of natural and manmade oilstones and i am having a little trouble with them. The natural stones were a breeze to flatten with wet/dry sandpaper, but the carborundum is proving to be difficult. Does anyone know a good way to flatten a carborundum stone? I have heard of doing it with diamond abrasives but there has to be another way, carborundum far predates the diamond method.
Also, does anyone know of a reference for identifying natural stones/hones? I have dark black ones, dark grey ones, variegated white/brown ones, and a white translucent one. Also some oddballs.
Thanks guys!

[Preston Baxter]

Carborundum is another name for Silicon Carbide which is one step below diamond in hardness. The reason the natural stones flattened well is that they are mostly Quartz which is softer. Aluminum Oxide or corundum (India Stones) is in between Quartz and SiC in hardness.

The wet or dry paper is most likely SiC, so you are rubbing SiC to SiC which wears both evenly and the stone usually wins.
This may be why India stones tend to be more popular with woodworkers as a coarse stone since they are a little softer than and can be flattened with SiC.

If you have three Carborundum stones you could lap them against each other, in turn, and end up with three perfectly flat surfaces. 1-2, 2-3, 3-1, 1-2 and so on. You have to have three though, just two can form spherical surfaces.

[James Taglienti]

Ah! thank you for stopping me from going into double digits on my sandpaper replacement costs :o
I will go out to the shop now and start rubbing the stones together. I didn't even think of that! I think it will help if i dance in circles and chant while i do it. I'll lock the door first.

[Jeff Willard]

Wait a couple of weeks. You need a full moon.

[James Taglienti]

shoot... i reserved the next full moon for my "ridiculous block plane sole flattening ritual" - i'll be lucky to finish it before sunup... i guess there's always next month.

[Tony Zaffuto]

Generally you can tell how fine a stone is by running your fingernail on it. Another method I use (for vintage stones) is by how ornate the storage box is. Better stones generally have better cases!

[Leon Jester]

shoot... i reserved the next full moon for my "ridiculous block plane sole flattening ritual" - i'll be lucky to finish it before sunup... i guess there's always next month.

It works better if you perform it under an apple tree in full bloom when the moon's full.

Work within a circle cast with Calvados to be sure. You can send the rest of the bottle to me. ;)

[James Taglienti]

I usually just use calvados on my water stones, it is a little lighter than H2O