In HC20 Hydraulic Rock Drill (or Hydraulic Drifter) systems, the Shank stop 86668811 (shank holding bushing) is a “shank stability guardian”—it wraps around the shank to keep it fixed during high-frequency impact (1300-1500 bpm). Montabert specifies a 400-hour replacement cycle because its gripping surface wears gradually: after 400 hours, wear depth often reaches 0.3mm+, weakening shank fixation and increasing vibration (reducing drilling accuracy by 15-20%).

1. Wear resistance: Heat-treated alloy steel (HRC 48-52) ensures it lasts the full 400-hour cycle.
2. Precision fit: Inner hole tolerance ±0.003mm, matching HC20’s shank perfectly to avoid looseness.
3. Stability: Smooth inner wall reduces shank wear while maintaining firm grip.