Originally posted by powderburner
Foam-core is the stuff sold at craft stores (2 ft x 4 ft sheets and smaller) and office supply stores (4 ft x 8 ft sheets) as a mounting or backing surface for large artwork. It has paper face sheets and a core made of foam that is usually about 1/4 inch thick. Cuts with X-acto blades, sands to shape with sandpaper, and for fine-tuning you can roll it on a hard surface to compress the perimeter. Foam-core can be installed with white and yellow glues and is more durable than the rest of the rocket materials. [/B]
Sorry I'm so late picking up on this part of the thread, ometimes we all skim
Cutting thick materials 14 and 28 ply Sho-card and Railroad board Is a bit more difficult if your only using an X-acto knife. I strongly suggest using any one of a number different type Circle and circular matte cutters available in most art supply, crasft stores and a lot of hobby shops. Pick one that will handle the sizes you cut most. No one circle cutter will handle everything. Be sure the model you purchase has replacable blades and is stiff. Compass types with beam attachments work, as do adjustable beam cutters. I'll post a pic of some that have proved up to the challange of cutting rings even in light plywood. I still cut most CR's in stacks of 10 or more on my band and scroll saw but individual or a couple can be handled with these tools easily.
Foamcore is a band name but is also used generically for a number of products with a light foam core sandwiched between 2 outer face materials of paper, cardstock, or styrene. Most craft stores only carry 3/16" and 1/4" thick "Foamcore" while 1/8" 3/8 1/2" and up to 3" thick materials like Gator foam, Jet-mount, FoamX and Ultra board can be purchased from all sign supply and most plastic supply houses. all in 4' x 8' sheets only, some of the thicker .010 styrene ultra board material can be expensive.at about $3.00 per Square foot..
Now the trick. If working with 1/4" or thicker foam core. punch a needle or pin hole as straight as possible through the material. I use a piece of scrap wood about 1/2" thick I drill press drilled a hole slightly larger then the pin in. With a pin tip dot the locations for easy finding on both sides. Set the circle cutter to the desired dia. and cut through the paper only from both sides. Finish the cut carefully about half way though the foam remaining with the cutter. presto accurate centering rings. This works with thicker material also but you have to use a knife to finish holding the blade as perpendicular to the foamcore face as you can. 3/8 and thicker rings don't need to be as exact as long as the cuts through the facing materials are accurate. I try to make them on the tight side.
PS Plain old styrofoam can be shaped the same way... from both sides.
Hope this helps.
