17-4PH Hard Stainless Steel Medical Drill Bit; Hole Opener; Passivation Treatment. 420J2 & 17-4PH Stainless Steel Medical Drill Bits / Trephines Category Details Product Description These professional-grade medical drill bits and trephines are precision-engineered from two distinct high-performance stainless steels to meet specific surgical demands. 420J2 provides exceptional wear resistance and cutting edge retention, while 17-4PH offers superior overall strength and