A reamer bolt is widely used when clamping a joint subjected to large shear forces. It has been postulated in some conventional joint design procedure that the applied shear force is transmitted only through the normal force exerted on the cylindrical body of reamer bolt. However, it is also supported, to some extent, by the friction force on contact surfaces involved. Accordingly, in order to establish a design procedure that takes account of the joint safety and efficiency, it is primarily important to evaluate the ratios of the shear forces supported by the reamer surface and the friction force. They are quantitatively evaluated by defining shear force transfer ratio (SFTR). It is predicted that SFTR is largely affected by the fit and the surface condition of the interface between reamer bolt and bolt hole. In this study, the amounts of SFTR are evaluated using three-dimensional FEM as contact problems. Numerical results show that SFTR by the friction force is significant, which implies that the conventional design procedure for bolted joints tightened by reamer bolts needs to be modified. The validity of the numerical analysis proposed here is demonstrated by experimentation, in which measured are the bending stresses in reamer bolts under shear loads. It was found that the numerical results favorably agreed with the experimental ones.