Why the timber context, I wonder.
Conical = cone-shaped
Burr = A burr (cutter), a small rotary cutter used in dremels for metalworking (Wikipedia)

Burr Grinders
"Burr grinders crush the beans between a moving grinding wheel and a non-moving surface. The positioning on the burr is what regulates the ground size, which allows for a more consistant grind. In the burr category, there are two different types."

"Conical Burr - The best grinders you can get are conical burr grinders. The burr spins slower than the wheel model, which makes them quieter and less messy. You can use a conical burr grinder for oily or flavoured coffees and it's not likely to clog, like the other kinds of grinders. These are the best type, but you will pay the price for them."
both explanations from http://coffeetea.about.com/od/grinding/a/bladeburr.htm

"Los molinillos con cuchillas cónicas preservan la mayor ..."
http://www.nuestrocafe.com/cafe_molido.php