Very quick take on how we make sills for our box sash window frames. We use our Centauro Alfa CNC machine to do all the notching of the inside and outside facing and trenching for the pulley stiles. The machine isn't really designed to do this but if you get creative you can adjust the macros to do a lot more than just hinges and lock mortices. We always use solid Sapele for sills as they will always last and the price hasn't gone crazy like other species. Yet.
