Lignum vitae was used as bearing material in nuclear submarines as recently as the 1970s, end-grain set to rub against steel main drive propeller shaft where it runs through the hull, wood blocks adjustable as they wear, lubricated by the oils in the wood, and cooled by the slight flux of sea water and oily fresh water in and out of the bearing. I have seen hard maple (sugar maple) knots used as bearing material in a late 19th century turbine water power with vertical wooden shaft, wet service duty at the bottom of the shaft, within the cast iron turbine housing, a knot of wood with a "football" shape was set into the end of the shaft, and it fit into a socket made of the same wood set into a square socket in the cast iron housing. Location: southern New Hampshire. John www.HistoricHomeWorks.com -- To terminate puerile preservation prattling among pals and the uncoffee-ed, or to change your settings, go to: <http://listserv.icors.org/archives/bullamanka-pinheads.html>