Hydraulic vs Mechanical Tool Holders for Gun Drills
The tool holder connects the gun drill to the machine spindle. The holder runout directly affects hole quality, tool life, and process consistency. A holder with high runout produces oversized holes, poor surface finish, and premature tool failure. I treat tool holder selection as a process-critical decision, not an afterthought. How Each Holder Type Works Hydraulic tool holders use oil pressure to clamp the drill shank. Turning a screw pressurizes oil in a sealed chamber, which expands a thin steel sleeve that grips the shank evenly around its full circumference. The clamping force is consistent and does not deform the shank because the pressure distributes uniformly. A hydraulic chuck gives the same runout every time regardless of operator skill. ...