Black Slate Engraving

[Leadhead]

Is it a viable proposition to do light relief engraving on old slate tiles?
I guess one would use solid carbide. If by chance you have any experience of this technique. I would be grateful for any advice. Speeds and feeds etc. for max. 1mm. "z" depth.

[gavztheouch]

You may have already looked into this but laser etchers/cutters do a great job of engraving into slate and granite. It just barely scratches the surface though, so im not sure it will get down as far as 1mm.

[phill05]

Yes it is possible to cut slate with carbide but the cutting edge has to be ground to a different angle to give a small back relief to preserve the cutting edge, in reality you are grinding the stone not cutting it, If you want 1mm deep you would do this in 1 pass.

Your cnc machine also needs to be very rugged with water flood.

The image below shows a 2.5d relief that is 8mm high for the flower and 6mm high for the text all the stone between is ground out with 2mm roughing passes then change to a V cutter to do the relief in 2mm passes.
as regards feeds you need to test cut on each type of stone, on old stone that has oxidised/hardened you will find it is slow.

Phill


http://www.mycncuk.com/attachment.php?attachmentid=13666&stc=1

[Leadhead]

Gentlemen - Thank you.
I posted prematurely before discovering the extensive amount of web info available.

My router is a small light piece of kit purchased specifically for this to avoid the obvious corrosion/ erosion to the main mill. So unfortunately will only be capable of light cuts and small step overs. Currently working out the screw protection for it and perhaps machining in a fabricated plastic bath??
As to coolant, assume tap water is OK or are there any obvious additives?
Will trial with existing single flute D bit carbide bits. But saw some 4 square unfluted 60 and 45 deg. cutters being used. Which would be easily ground and resharpened from broken stubs. Any info on that appreciated.

[Bumps]

I do quite a bit of engraving with my cnc on slate and other materials. I use a drag bit they are not cheap but they do a great job. you can see them here: http://www.widgetworksunlimited.com/CNC_Diamond_Drag_Engraving_Bit_p/cnc-dmnd_engrv-250.htm