.Chapter One Mechanics Components第一章机械构件Lesson One第一课 齿轮Words and Expressions 1.spur gear直齿轮2.thermal expansion热膨胀3.lubrication润滑4. backlash倾向间隙5. the pitch circles节圆6.space width间隙宽度7.instrument gear仪表齿轮8.the split gear拼合齿轮9.helical gear斜齿轮10.pitch-line velocities节线速度11.an axial thrust轴向推力12.blank坯件13.double-helical gears人字齿轮14.non-intersecting不相交的15.worm gears 蜗轮蜗杆16.bevel gears伞齿轮17.crossed-axis交叉轴18.nut 螺 母19. screw 丝杠，螺钉20. large r
