TS(abridged from Torque-Shear) bolts are originaly developed for the purpose of quality assurance in clamping force by means of fracture mechanism due to the stress concentration around the V-type notch at the bolt tip. In the control of tightening a bolt, torque factor as well as geometries of the notch (diameter, angle and roundness) are of prime importance to assure the quality of the joint performance in a structure. Some theoretical aspects of fastening torque and clamping force in a TS bolt are examined with focus on the friction coefficients. A simple relationship between face friction coefficient and thread friction one is derived, and numerical calculations and plots based on the experimental data are presented, which may be used as a complementary guide in a situation to cope with torque factor degradation. It is found that the interaction between friction torque on the thread and the tensile force defveloped in a bolt leads to an elliptic stress space. The upper limit of thread friction coefficient ${mu}_s$ and the lower limit of face friction coefficient ${mu}_w$ are derived and plotted against the axial force ratio.