A.0.2m~0.5m B.0.3m~0.5m C.0.5m~1.0m D.0.5m~1.5m
A.1/3 B.2/3 C.1/2 D.3/4
A.跳孔間隔;先外圍后內部 B.逐個連續(xù);先外圍后內部 C.跳孔間隔;先內部后外圍 D.逐個連續(xù);先內部后外圍