I have turned several types of plastic pen blanks using carbide tools both regular and negative rake. For all of them I use the maximum speed my wood lathe will go, about 3500 RPM. I have never had a problem with heat/melting during turning but I have had heat problems when drilling without using a good drilling regimen.
Of the plastics I have turned, Alumilite urethane resin blanks seem to turn the easiest. I think they are likely the softest of most commercial plastic blanks. On a scale of 1 to 10 where 1= it almost turns like medium hard wood like maple and walnut and 10=problematic and most difficult, I rank Alumilite urethane blanks at 1 or 2. Because it is a softer material, I also apply a couple of coats of CA to finished blanks to help them retain their shine longer. I also favor Alumilite because it is one of the most readily available resins for casting one's own pen blanks.
Kirinite blanks are more of a true acrylic resin material made by Kirinite in Illinois. It is a thermoset acrylic resin that is made by adding thin strands of polyester coated paper to the resin in different directions to create swirling patterns and colors. It is durable and tough as well as being resistant to chipping, cracking, shrinking, and warping. Kirinite was originally introduced into the knife making industry as a handle material because it isn't slippery even when wet and it can be shaped using conventional woodworking tools. (Most Kirinite is semi-transparent so painting the inside of the drilled hole or the brass tubes is highly recommended). On my scale of 1 to 10 I would rate Kirinite at a 5 or 6 for less experienced turners and a 4 or 5 for skilled and experienced turners.
Rhino or RhinoPlastic blanks are made from a special blend of polyester resins. This material was specifically formulated for pen turning. It is on the hard and brittle side which seems to be typical for polyester blanks. Rhino blanks are a prime candidate for cutting the blank longer than needed, drilling to the depth of the pen tube, and then cutting away the excess to expose the hole. This significantly reduces the chance of blowout which seems to happen most often just as the drill bit breaks through and starts to exit the blank. Most of the Rhino blanks I have turned feel hard but usually have well defined and relatively sharp and chip-free edges (on the blank). On my 1 to 10 scale I rank Rhino as a 6 or 7 for an experienced turner and a 7 or 8 for a novice.
Like many pen turners, Inlace Acrylester, another polyester resin. (I think it is made by the same resin manufacturer that make the resin formula for Rhino blanks). It is made to support a higher volume of pigments and fillers which permits it to have rich, vibrant, and spectacular colors. Inlace Acrylester is Trademarked and owned by WoodTurningz. Raw Inlace Acrylester blanks are typically very hard and brittle and almost feel like glass. It can be a very "chippy" material and even the manufacturer recommends not drilling through the bottom of the blank, but leaving it long and cutting off the excess to expose the hole after drilling. They also recommend making light cuts using very sharp carbide tools preferably with Negative Rake Cutters. As they say in their documentation, "Aggressive cuts and Inlace don't mix" and dull tools can cause severe chipping. Due to the instructions provided by WoodTurningz, personal experience, and the reported experiences of many IAP members, I would rate Inlace Acrylester as an 8 to 9 for experienced turners and 9 to 10 for those with less experience - they do make gorgeous pens though!
There of course are a whole host of other trade named blanks and materials that fall between Alumilite and Inlace Acrylester, each with it's own type of resin and associated turning characteristics. These are just some opinions from my perspective and personal experience using a few of these plastic materials. - Dave
