Carving on stones

[scottcox]

Tom,

How did you treat the foam before pouring? Sand and seal? Any release agents involved?

Scott

[jhicks]

Don, I believe that's what I was told about the cause but never heard the 2nd part about starting out with a cooling agent and cutting with it. Thanks. I think I'll stay with other materials and leave the hard stuff to others while monitoring for photos.

[don]

Until I'm able to leave my day job( really 2nd shift) I'm cnc toolgrinder and make\regrind carbide mills,drills and various other cutters. If you can imagine it, we can make it. We flood the tool with an oil coolant while regrinding\manufacture. And the above information is correct about using any kind of coolant after the tool gets hot, it will make microscopic cracks and become brittle and break down or break apart, sometimes immediately.

I've engraved my business card and the customers logo into granite and marble. I was using 3flute 60degree v-bit with a shear angle that I made. I haven't used any form of liquid to cool the tool while machining. (to avoid the mess) Instead I use a cold air gun simular to this one. http://www.vortec.com/cold_air_guns.php
On the acrylic of my dust skirt I've drilled and tapped a hole for a fitting with a short flexable nozzle that point towards the cutting tip. I have a small valve to regulate the air flow, so the dust collector can pick the dust up.

I haven't tried any large projects, the largest was the business cards and the logo of the potential customer.(scaled up to 6"w x 3.5"h)
I used the same feed and speeds for both Granite and Marble. If I remember correctly feed was .3 inches/second and spindle speed seemed to be the best around 10500-12000.

Will be experimenting again as soon as I'm able to find time to grind a different cutter that I'm attempting to design.

Don

[jhicks]

Don, that looks like a cool solution. If you develop a custom bit geometry that seems to deliver, I think you might find a market for some. Let me know how your trials go. I would be interested in more agressive cutting but one step at a time I guess.

[drodda]

Don,
What are you doig waisting all this time typing? Get designing that cutter. we are all waiting for your results so we can flood you with requests for the cutteers.

On a more serious note. We appreciate your input on cutters. Seems like you have probably forgotten more than I already know about them.

I have been looking into the cooltool air cooling for some time now. Just have not jumped and bought one yet.


Dave

[dwight]

Don,
I too need your bits as I have been asked to route etchings and letterig in polished granite and have NO idea where to get the bits or what feed rates or spindle speeds to us as I use a simple trime router for my wooden signage

[rcnewcomb]

Be prepared for sticker shock on diamond bit prices for granite work:
external link to Diamond Bits

[donchapman]

I've hand carved and sandblasted stone for several years. The scorpion is shallow hand v-carved into slate floor tile which is so soft it can be carved with woodworking chisels. The dogs are hand carved into Texas limestone, also soft enough to carve with woodworking tools. The fancy tombstone is Vermont marble and the decorative carving was done by Joseph Kincannon of Archaic Stone Carvers in Austin, TX. I then spent about 80 hrs. hand v-carve lettering the inscription with carbided tipped stone carving lettering chisels I ordered from England. The black negative mask I used for layout. The Psalm I sandblasted into sandstone after cutting a mask with my vinyl cutter from Hartco sandblast masking mtl.

I've experimented briefly with trying to shallow dry v-carve limestone tile with a woodworking carbide v-bit on my ShopBot and the bit heated up very quickly so I stopped. However there is a thread somewhere on this site of some folks who have used VCarve Pro to do some dry CNC routing successfully.

I suggest anyone attempting CNC routing of stone try the soft stones like limestone and slate and go very shallow and see the problems and results before attempting harder stones. Granite is very hard. Marble varies but is much softer than granite but harder than limestone and slate. Sandstone varies in hardness but is always extremely hard on tools and dangerous to breathe the dust.

For most people, sandblasting may be the easiest option. You can mask the stone and have someone else blast it. However sandblasting does not provided the wonderful shadow/light contrasts of v-carving



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[myxpykalix]

There is a soapstone dealer in town here and once i bought some for a person to carve some stuff with it that turned out nice. However it was handcarved and with small dremel type tools not on a bot. Point being if a small tool and hand tools can do it a bot can do it (maybe). But this was smaller rocks not boulders.

[donchapman]

Jack's right. Soapstone should rout easily on a ShopBot, although I've not tried routing it myself. I have handcarved some and it's so soft and easy that I forget it's a stone.