[verhoevc]

I have purchased some slab cut (1.5mm) synthetic opal material. I want to use it for inlays but as I understand it it is very high in silica content and I'm therefore assuming quite abrasive. I can't seem to find any info on bit types to use for it or speeds/feeds. Any help would be appreciated!

Here's some spec from their data sheet:
SIO2 80% resin 20%
Specific gravity 1.89
Hardness (MOHS): 4.00
Heat resistance 130*C

Best,
Chris

[awerby]

Like this stuff: Synthetic Opal - Black Opal, White Opal, Crystal Opal and Fire Opal ? It says it's 4-5 on the Mohs scale, so that's pretty hard. If you really want to cut it with a mill instead of using a lapidary process, I'd suggest trying a PCD endmill and lots of coolant. Make sure your mill's sliding parts are protected from the abrasive slurry it will generate in cutting.

[warrenb]

Water coolant and carbide endmills should work.

[verhoevc]

It's funny that y'all mention water coolant as I have some specialty bits from precisebits.com that u see to cut mother of pearl, abalone, etc without coolant. I've read that that has a hardness of 3.5 and as high as 4.5 sometimes.
Probably won't hurt to cool... I'll have to build some sort of bath for my table then so I don't screw up the waste board I have on my Shopbot.
Best,
Chris

[mactec54]

I have purchased some slab cut (1.5mm) synthetic opal material. I want to use it for inlays but as I understand it it is very high in silica content and I'm therefore assuming quite abrasive. I can't seem to find any info on bit types to use for it or speeds/feeds. Any help would be appreciated!

Here's some spec from their data sheet:
SIO2 80% resin 20%
Specific gravity 1.89
Hardness (MOHS): 4.00
Heat resistance 130*C

If you need to use coolant, just make a tray or buy one and submerge your part in water, or if you have a pump to supply the coolant, then just low flow low pressure, is all that is needed, if the sides of the tray, are high enough there will be no mess, diamond cutters and diamond grinding wheels are best for any of this type of work

[steve pies]

i second Mactec54 post. you really want to use diamond for this. there is a lot to know about diamond grinding but i would start with a diamond plated tool. and use a water based coolant or just water if you have too but becareful you could mess up a pump with the swarf getting in the pump. my thinking is higher spindle speeds will work better (over 3000) and slow feed rates (try F5. IPM to start) i dont know how much material you plan on removing, a 150 grit diamond will probably be able to make a .0100 depth of cut no problem.