Materxals and L1jbrication for Gear and Bearing Surfaces in Uhv”

During design and construction of the SLAC polarized LEED (PLEED) system, a search was made for a dependable gear, bearing, and lubrication sysLem for .the. computer-controlled Faraday cup used to measure diffracted beams. Components must be nonmagnetic, bakeable to 250” C, and at room temperature must operate at pressures in the 1O-9 to VYio Pa range. A test system was constructed which incorporated a meshed pair of dissimilar pitch diameter spur gears, one of which was conftied I-o (by bnshings) and rotated on a fixed shaft, while l;he other gear was liven by a commercial. rotary motion feedthrough which was rotated by a servo motor driven in sine fashi.on with a clirecl;ion reversal every six turns and peak spBeds of 50 rpm. The criterion for a successful pair was N lo5 turns, the life rating for the feedthrough. Pairs had actual turn counts from less than 1 to 91, 000. Materials for gears included stainless steel, beryllium copper, mcl aluminum al.l.uys. Zuhricants used singly and in concert were MoS2, WS,, Ag, hard chrome, .??d P. MoS,-graphitesodium silicate mixture. The successful. gear pair was Ag-plated AQ alloy and >10S2graphite-sodium silicate-costed BeCu. Subsequent performance in the PLEED system after repeated bakecuis will also be discussed.