The Golfsmith Cobalt Steel Pre-Reaming Drill Bit is perfect for re-boring hosels on club-heads made from notoriously difficult-to-drill metals such as 17-4PH, titanium, & marraiging steel. This HSS-CO alloyed & titanium-nitrated drill bit holds its rigidity & hardness at higher temperatures better than a HSS drill bit. Sized for enlarging hosel bores prior to reaming, this drill bit provide a good epoxy bond allowance between shaft & hosel.