The RF/DF mechanical chuck is designed with three large external sliding chunks, while it uses the cam structure inside. The expansion of the sliding chunks is done by the pushing of the cam structure, and the expanding sliding chunks then tighten the paperboard core and realize self-centering. Main features: Shaftless design for quick and efficient reeling and unreeling. Excellent paperboard core holding and tightening realized by the sliding chunks with large contact area and high stability, to avoid problems such like slipping, loosening, core breakage and etc. The locking force reinforced by special convex-concave texture of the sliding chunks. The cam structure provides even clamping force by use of self-weight. Maintenance-free structure with low friction force. Special excellent alloy steel material is adopted with great durability for high load capacity. Excellent paperboard core holding and tightening realized by the sliding chunks with large contact area and high stability, to avoid problems such like slipping, loosening, core breakage and etc.