Corian, Soapstone, and graphite?

[jhicks]

I am discussing these three materials with some folks and thought I would ask for input. Checked archives but not much on soapstone or graphite, some on corian so here goes.
Application 1 and 2 are carving in soapstone and corian for counter top companies.
Standard questions on bits, speed, feed, depth, and cooling?
2nd ? on depth of cut to produce a backlighted light box in corian/solidsurface materials. How much material does one leave on the bottom when carving to produce a "light through" the surface when back lighted? Not lithophane quality but lighted features, artwork, letters etc.
Do V carves work Ok or only flat bottom clears?
3rd, Anyone compared the new V carve photo software yet for lithos or photo vs others on such materials?
4th, is Soap stone. Saw the various hardness notes in archives but none on what cuts, cooling, or speed, feed, depth etc. Probably V and end mill cust are required for counter backsplashs etc.
Material is vermont talc and will make sure its NOT the hardened version.
5th, Anyone used soapstone for glass molds? Originally heard they were often made in Graphite but since learned Cherry as well so its either Cherry or maybe Soapstone?
6th, is dust on all above. I heard from Mike in Michigan "NOT TO CUT GRAPHITE" as dust could ruin the spindle. (Phew! Thanks Mike)Heard from someone Corian dust penetrates wood in the shop and you can never get it out of your stock.
So now I wonder about soapstone dust and any damage on equipment, shop supplies, or other issues folks may have knowledge about we need to consider and take precautions for before we make a commitment and lose a spindle.
Have decent dust collection and vacuums for hold down if needed so unless the dust ignites I think those areas are ok.
I know this is a lengthy list so All input on any question is appreciated. Feel free to e-mail direct if too many for a concise reply on the forum.
Thanks

[Brady Watson]

Jerry,
You have quite a bit of area to cover..but I'll offer my experience with some of them...

1. Graphite...I am assuming that you are referring to the homogenous graphite refractory blocks? Carbon fiber is often referred to as graphite as well. In that case, I have cut over 1000 sq ft of that and my spindle is still going strong. The homogenous blocks throw of a nasty fine powder that will tear up not only your spindle but YOU...so be careful. If I HAD to cut this stuff, I would think about using water to keep the dust at bay...and then you need a plastic spoilboard. Depending on how much of this stuff you want to cut...it may be best to sub it out to someone else.

2. Soapstone...Cut it once dry. Came out really well. It is hard, but hardness can be misleading. You can use carbide tools dry and/or spritz it with a spray bottle and water to cool it if you are doing extended cutting. If you are going into production an auto-mister would be a wise investment. Flood cooling is probably not necessary. My biggest concern would be ramping into the work to avoid shocking the router bearings and shattering the bit. Use an endmill.

As a general note, when I try cutting new materials out of the norm, I start off with light chiploads and about 13,000 RPM with a slow move speed. Judging by the chip that is coming off of the bit and the overall sound, this tells me what to do next to get it dialed in. In some cases, such as plastics, I do the opposite and go fast to start, then slow down if necessary so that I don't melt the material.

-Brady

[jhicks]

Thanks Brady, I think I will avoid Graphite since it appears cherry or perhaps Soap stone may work for the blown glass molds. You say end mill on soap stone, does this imply v carving patterns for letters or a customized vector drawing is a concern or just haven't tried it yet?
Thanks for the feedback. Anyone else on the corian questions and thicknesses for backlighting?

[Brian Moran]

Jerry,
There is a post on the Vectric forum at http://vectric.com/forum/viewtopic.php?t=46&highlight=stone which shows an example of VCarving into soapstone with some information on the bit and tool used. I believe that part was cut on a dedicated stone cutting machine so you may need to be a bit more conservative with feeds etc.

Hope this helps

Brian

[luke]

Brady could you expand your response on cutting graphite a little. I am interested in cutting carbon graphite flat panel and tube stock. I have been trying to choose Onsrud bits for my PC but am finding it increasingly difficult. I want to be sure especially when prices range from $50 to $350. I am trying to obtain clean cuts on both surfaces. For saws is a diamond cutter better than carbide. For mills do you cut with 2 or 3 flute, carbide or diamond coated.

[Brady Watson]

Luke,
When working with carbon fiber or aramid sheet, diamond is the only way to go. They last at least 10x longer in my experience, and give a polished edge to the part because of the micro diamond particles that are on the surface of the end mill. These are not the rasp-looking ones that they sell for cutting fiberglass etc; they look like a flat black coated end mill. I use OSG diamond coated PCD (poly crystalline diamond) end mills. I use the 1/8" size for the runs of parts that I do and they run me about $50 each in quantity. They are about $72 ea. They are the difference between doing the job and not. Try to steer clear of the DLC coated ones (diamond-like coating) because they really don't do what the real PCD ones do. There are times where a down-spiral (really a left-hand endmill) are a good choice, but they are only available from a few suppliers and are pretty pricey in comparison to the regular end mills (like an upcut spiral). Vacuum with gasketing or DS tape work well for holding the stuff down to counteract the upcut pull you get from the spirals; this is especially true when you cut really thin laminates.

-Brady

PS- A word to the wise...the diamond coatings (and most others for that matter) do not work with the z-zero plate since they act as insulators. You have to manually set the Z-zero...nothing like flushing $50 down the drain because the Z mashed the bit against the plate and shattered it (I have a 7.2:1 Z...so it totally killed the 1st one)

[luke]

Thank you Brady for the quick response. Your thoughtful PS has most assuredly saved me $50. The 1/8 size bit is exactly what I am looking for. It surprised me that Onsrud does not make one with a ¼ shank. I hope I am not digressing too much from Jerry’s original post by asking, but are you referring to the Exocarb 7020 line. If you have bit number handy that would be great. Diamond equals 10x longer life. Is it possible to get 1000 feet from lets say cutting 1/16 graphite panel.

[Brady Watson]

Yes. The ExoCarb line of tools is what I use. I'll have to got out to the shop to check the #. Not sure off the top of my head how far it will go on your tool, but make sure you have your chipload dialed in...heat really kills them. Dust collection is a big help with cooling the bit.

-Brady

[jim_ludi]

Brady - Could you elaborate on the safety issues involved with working carbon fiber or aramid sheet?

[Brady Watson]

Jim,
The biggest thing is dealing with the dust and not breathing it in. If you are using dust collection, you have to be careful when you empty the bag because there is very fine graphite powder created when cutting carbon. Our lungs are not really equipped to deal with it since it goes past the guard hairs in your throat and becomes a permanent part of your lungs...So by all means, wear a respirator when working around the stuff. Even though you may be putting off a good chip while cutting it, there are many particles in the air that you cannot see until you take a break and clean your nose.

The other danger is splinters. Carbon and aramid fibers are very stiff and brittle. If you are handling the sheet stock, often times the edges will be jagged. A carbon splinter feels like a steel splinter...except it breaks off when you try to pull it out and can hurt for weeks...so protect your eyeballs and hands!

None of this is to scare anybody off from cutting these materials...just exercise caution when working with it.

-Brady