October 31, 2013 at 11:48 pm #21488
They’re custom machined out of Delrin. They slide directly on the wood, and the friction is generally negligible compared to the rest of the system. We verify this by turning it upside down, and seeing that it doesn’t change much. ;)
There are some polargraphs made with the EBB– that’s how quite a few of them got started.