38mm Diameter R28 Thread Threaded Button Bit With YK05 Tungsten Carbide Inserts For Top Hammer Rock Drilling The 38R28 threaded button bit is engineered with YK05 grade tungsten carbide inserts for dependable performance in rock drilling. Its R28 thread configuration is optimized for lightweight top hammer rock drills, minimizing the tensile shock waves transferred along the drill string. Improved fatigue resistance lowers wear rates, delivers a stable penetration speed, and