As is typical for SPIF, the bending ratio t0/R plays an importantrole in the failure mode. Thus, for the smaller tools (6 and 8 mmradius), the mechanism of failure is ductile fracture with a com-plete suppression of local necking. For the larger tool (10 mmradius), the mechanism observed is ductile fracture with post-poned necking at the very early stage.