多年来，人们越来越需要在燃气轮机叶片等零件上加工小直径深孔。自20世纪60年代以来，阀杆工艺已被用作在高温合金零件上钻孔的经济生产工艺。实践证明，该工艺具有足够的灵活性，能够适应涡轮叶片设计师日益复杂的要求。

FOR MANY YEARS, THERE HAS BEEN AN INCREASING NEED TO MACHINE SMALL DIAMETER DEEP HOLES IN PARTS SUCH AS GAS TURBINE BLADES. SINCE THE 1960S THE STEM PROCESS HAS BEEN EMPLOYED AS AN ECONOMIC PRODUCTION PROCESS TO DRILL THESE HOLES IN SUPERALLOY PARTS. THE PROCESS HAS PROVEN TO BE FLEXIBLE ENOUGH TO BE ADAPTED TO THE INCREASINGLY COMPLEX DEMANDS REQUIRED BY TURBINE BLADE DESIGNERS.