国 上济充大学 English Classes2 2-Screws and nuts that need a closer tolerance than class 1 for a better quality fit between mating threads = suitable for general machine design applications. 3 Screws or nuts that may be used in clean environment for highly loaded threads where complete contact of the screw and nut is important. T=0.0015(d3+L。12+10p23) d=major diameter L.=engagement length p=pitch 41 圈上大峰 English Classes2 23 Nut 0.300 1300T 0975T Basic form 0.7507 1.C00T 3 .50 Screw 2A 1A Allowance and tolerances for classes 1A.18.2A.23.3A.and 38.Source:Abstracted from Unified Screw Threads (UN and UNR Thread Forms).ANSI B1.1-1982.American Society of Mechanical Engineers.New York.Reprinted with permission.41 English Classes2 2 - Screws and nuts that need a closer tolerance than class 1 = for a better quality fit between mating threads = suitable for general machine design applications. 3 - Screws or nuts that may be used in clean environment = for highly loaded threads where complete contact of the screw and nut is important. T = 0.0015 (d1/3 + Le 1/2 + 10 p2/3) d= major diameter Le = engagement length p = pitch 42 English Classes2