Engraving and carving stone, I'm Confused

[foamcutter]

Ok, I'm confused. I am in the process of desiging and building a router/mill. My main use for it will be carving and engraving stone, granite, marble and some soapstone, slate, you get the idea. I also would like to be able to mill on aluminum and mild steel. My confusion is what do I use as a spindle? From what I understand so far, stone, steel and aluminum should be done with a lower speed spindle, and slow feed rate. But I see some posts where guys are milling alum at 10,000rpm. Please help me out guys what spindle speeds should I be looking at for those materials? Also any suggestions as to a spindle? How about tooling to cut with? Thanks Ron

[andy_ck87028]

I just saw this thread and have been making my own enquiries re. cutting with stone.

Router spindles will vibrate out of control as the stone is made of a composite material that is not consistent in hardness.

I have thought about it further and wonder whether a die grinder attachment might provide an answer.

Alternatively, an abrasive water jet attachment.

Andy

[ger21]

Commercial stone machines use diamond tooling, with water cooling (lots of water). I have no idea about spindle and feed speeds, though.

[cbass]

I've been doing just this kind of research myself.

http://www.stoneadvice.com/forum/ has been a great resource for this.

If you plan on using bits from the stone industry (i.e. profiles, figer bits, diamond tooling etc) you'll need a spindle that accepts what's known as 1/2" Gas bits. Basically they are bits that are threaded (i.e. not a collet system). I haven't been able to get an exact dimension on the diameter of the thread but I think its close to 1". You might be able to make an adapter that goes from a thread to a straight shank so you can use tham in a regular spindle but I don't know how succesfull this would be (too much Flex/run-out).

Instead of trying to re-invent the wheel, I've been considering the following.

The first is an edge milling machine...

http://www.toolking.com/portercable/view.asp?id=14682

The second is more of a typical router...

http://www.omegadiamond.com/catalog/...products_id=31


There is a considerable weight difference (1st is about 22 lbs/ 2nd is about 70 lbs). Both allow through spindle water cooling.


This is a great catologue that gives you an idea of the bits and machines available (with Prices!).

http://www.granquartz.com/Acrobat%20...0&%20Drill.pdf

http://www.granquartz.com/Acrobat%20...20Machines.pdf

Finally, if you have specific questions, give the guys at http://www.granitecitytool.com/ a call. Just don't tell'em I sent you I think they're tired of my questions...

[trevorhinze]

I won't pretend to know anything about working stone, but a search on ebay turned up the following tool which at 800 bucks isn't cheap, but it is alot less than the others I have seen. It also comes with a free bit!


http://cgi.ebay.com/1506VR-Flex-30mm...QQcmdZViewItem

[smarbaga]

hello:
the stone engravers that i have seen:
first cut out a rubber shield with a heavy duty vinal cutter.
this is places over the the flat granet work piece to prevent it from getting scratched and shield from over run.
a cnc sand blaster etches the actual image.
the compant (granet ambelage ) had a 12 foot diameter diamond water cutting saw on a railroad track to slice huge pieces if stone.

[Switcher]

You should talk to "rab" here on the forum. here is a link to his site.

http://www.rainnea.com/custom-stone-carvings.htm

http://www.rainnea.com/cnc-boko.htm

[Geof]

This link will show a video of an almost standard metalworking machine being used for cutting granite. The most significant adaptation is improved filtration capacity in the coolant system.

http://www.haascnc.com/news/new_file...%20Granite.wmv

[trevorhinze]

That was an interesting video, Thanks for the link!

[MonoNeuron]

Hi Foamy,
There used to be a site on the web run by a bloke by the name of Marty Harper who cut pictures into marble and granite etc using a standard milling machine / mill drill. For the cutter he used just a normal round length of carbide sharpened to a point much the same as a nail point (4 sides at about 60 deg) which he said worked well as long as you had LOTS of water flowing over the cut to keep things cool.
I can't quite remember how fast the spindle went but I would think around 6000 to 9000 revs would be ok on a 1/4" bit. He used DeskArt and had a step over of about 5-7thou and much work was done to the pictures before cutting them. They all turned out very well and took a few hours to cut. About 4" square I think.
It's a shame the website isn't running anymore but if anyone knows of him then tell him to get back out there and share some knowledge again as he was fairly proficient at it.
:-)
Richard.

[wjfiles]

I am building a router to carve stone amongst other things.
One of my hobbies and occupation was cutting Opal and I did a lot of carving buy hand with a Dremel. This was to be my first aproach using a Dremel and diamond bits and burrs.
I always used the plated type as they cut faster.
Speed was about 5000 rpm, the feed rate will be critical for tool life.
Too much feed will mine the diamonds out of the tool.
Granite is a harder material than I used to cut and I would be surprised if there was a carbide that would stand up for long.
Dental suppliers was my main source .
Some lapidary suppliers in the States sell a Water swivel the goes in the chuck and feeds water down the centre of hollow bits, mainly for core drilling.
Sorry for rambling on but maybe some food for thought was in order.
Bfiles

[MonoNeuron]

Hey wjfiles,
There are lots of different grades of carbide out there from super hard and very brittle to relatively soft used for intermittant cutting where toughness is required over brittleness. Personally I would use the hard grade. Here are a few links.
http://www.niagaracutter.com/techinf...feed/carb.html
and
http://www.basiccarbide.com/gchart.htm
These may help somewhat.
Richard.