A.30HRCB.40HRCC.50HRCD.60HRC
A.顶尖与擦版辊中心孔摩擦B.顶尖内部轴承的滚动摩擦C.顶尖与擦版辊中心点摩擦D.顶尖与擦版辊的滑动摩擦
A.1minB.2minC.3minD.4min