In this study, the influence of friction drilling tool pre-heating on mechanical properties of chipless manufactured internal threads in thin-walled AZ91 magnesium casting alloy profiles is investigated. In this context, the influence of manufacturing processes on microstructure and the resulting fracture behavior during mechanical loading are in focus for the determination of failure mechanisms. Two batches were investigated, whereas specimens were manufactured without and with pre-heating the friction drilling tool before manufacturing. The mechanical properties were determined in tensile and fatigue tests in tensile loading range. The mechanical results were correlated with the profile qualities in form of computed tomography analyses and hardness mappings. Light and electron microscopic investigations of fractured surfaces were performed to analyze the fracture behavior in cyclic tests. Process-related and stress-related work hardening effects were determined at the edge area of the threads. Differences in fracture behavior under quasi-static and cyclic loads were determined. Turns of internal threads connected to the threaded rod were sheared off in tensile tests without visible cracks on the exterior surface of the flat profile specimens, whereas cyclically tested specimens provided fractured surfaces for fractographic failure analyses. Crack initiation at thread root and two stages of crack propagation until complete failure due to overload fracture were investigated. Pre-heating of the friction drilling tool during manufacturing of the threads had no influence on quasi-static and fatigue properties, respectively.