I’ve been turning MDF discs. MDF is a plain material without visible grain. The discs need a hole drilled in the middle after turning, and I mark the spot for the drill with a little depression turned with a skew chisel. With this material it is not easy to see the exact centre of the spinning disc. Of course a pencil will mark a circle, but I found that if I make a quick random squiggle of pencil somewhere near the middle before mounting the blank, when it spins the centre magically becomes easy to see. This takes just a second when preparing the blanks.
MDF turns well
MDF is easy to turn, and I use it a lot, often laminated into blocks, though the fibres are a bit woolly when cut. I use the moisture resistant kind as it has a higher resin content and gives a better finish for painting. Some grades are better than others, and this shows when you cut into them. Turning MDF blunts the tools quickly, but the work on these discs is quickly and easily done with scrapers. They are very quick to sharpen if you have the angle set up on the grinder platform. I usually get two discs from one sharpening. I use a round nose scraper to rough out, then a square nose to refine the shape. Finally, another round nose to make the last cuts on the concave detail after the first has done most of the work. The shavings are very long.
It is much easier to turn from the face of the material than the edge because of its structure. MDF is quite strong, but can easily delaminate and split if small diameters are turned. It has a hard surface skin and a softer, more porous core, so sanding is always needed, and the exposed core needs sealing before finishing. You need to take care not to cut too deep into the soft parts when sanding. It’s easy to change the shape.
It’s very dusty to turn, and good dust extraction is essential if you do it often. Its dust is sometimes said to be particularly dangerous, but there is no evidence that I am aware of to support this. It is as harmful as any other wood dust, but not more so. If turning MDF is more dangerous than turning natural wood, I think that is because it makes more dust.