Re: Turning Acrylic
Ed Davidson
Doug,
In our woodturning hobby, you'll run across 4 distinctly different types of "acrylic". Most retailers will not tell you what compound they are selling (probably don't know), and will use the term generically across all types of materials:
1) Cast acrylic...usually professionally made, in large sheets or blocks and then cut to size for retail sales. There are a few ways to identify cast acrylic: small pieces like pen blanks will almost always have saw marks on the sides and small chips on the edges resulting from band saw cuts. And, if you cut a piece on your band saw, it will not melt. It also has a very strong smell (plastic) when being cut or turned. Most of what you'll find at large retailers like Woodcraft and Crafts Supply is cast acrylic. Very hard and dense. Many people have success turning it with carbide cutters. Tends to chip (looks like shattered glass) if turned aggressively, or with the wrong/dull tool.
- Extruded acrylic...aka, Plexiglass. This stuff is not intended for turning, but sometimes ends up in retailer's inventory. It will melt if cut with a band saw or just about any other type of power saw. Don't waste your time trying to turn it.
- Polyester resin...known as a home-brewer's compound, mostly cast by amateurs in small batches. This is the stuff I used for years to cast "EPR" (Ed's Poly Resin). Relatively soft and easier to turn than acrylic and with less smell (IMHO). Use scrapers and skews. Tends to chip (looks like shattered glass) if turned aggressively, or with the wrong/dull tool. Poly resin is not as popular as it once was, but you can still buy the raw materials to cast-your-own at Michaels and Hobby Lobby. One of the more common brand names for the two part mix is Aristocrat. I'm pretty sure that the soft version of "Tru-Stone" uses polyester resin mixed with power-fine crushed stone, as it has exaclty the same smell when it's turned.
- Alumilite...also a small batch, mostly hobbyist and amateur two part mix, that tends to develop bubbles as it's mixed and requires the use of a pressure pot to extract the bubbles as it hardens. Turns about the same as poly resin. Some people like it better than poly resin, some don't (controversial subject). Just about all of the more exotic pen blanks you'll find at Penn State and a few other retailers are made from Alumilite...snake skin in clear resin, coffee beans in resin, stars and stripes colored blanks, Canadian flag blanks, zebra skin and other "animal print" blanks. Alumilite is also used to stabilize punky soft wood like Box Elder burl and to add brightly colored plastic square corners to hybrid (rotten wood/resin) blanks.
Hope this helps.
