Collars and hollow pieces shall be made from ingot or cogged ingot sections competently punched, bored or pierced before the parts are reamed or rolled over a suitable mandrel.

• 部件在滚轴上扩张或者滚压之前，用纯铁或初轧钢锭制作的颈口件和空槽件必须冲压，打孔或者钻孔。