The Spline Shank 86732575 is a key torque-transmitting component in HC25 Hydraulic Rock Drills, connecting the drive system to the drill shank while guiding its reciprocating movement. Generic spline shanks have low surface hardness (HRC<42) that leads to tooth wear within 500-600 hours, reducing torque transmission efficiency. This OEM spline shank undergoes heat treatment to achieve HRC 50-55 on its spline teeth, with a wear-resistant coating (≥0.02mm thick) that limits tooth wear to ≤0.03mm over 800 hours. Its precise spline geometry ensures smooth torque transfer and guidance, maintaining ≥95% efficiency until mandatory replacement.