The aim of the present investigation is to establish a testing method suited for determination of in-hole dynamic force-penetration data for non-uniform standard percussive drill rod-bit configurations. The method is based on a version of the method of two-point strain measurement, which permits non-uniform rods, i.e. rods with variable characteristic impedance. This version allows normal force and particle velocity to be evaluated at an arbitrary cross-section of a homogenous non-uniform elastic rod from strain measurements performed at two different cross-sections of the same rod. The main problem of this investigation is to assess whether the influence of threads can be considered insignificant. As a part of the study force-penetration relationships have been determined for the penetration of a standard Sandvik Rock Tools button bit into Swedish Bohus granite.