Experimental investigations were carried out using a custom-designed testing stand to develop axial force–torque diagrams for threaded fasteners. The research focused on evaluating how different assembly parameters affect the relationship between the applied tightening torque and the resulting axial force. The studied parameters included screw size, strength class, the use or omission of a bearing element under the screw head, and the rotational speed of the tightening tool. The obtained results allow for comparative and variance analyses, enabling the identification of key relationships between assembly parameters and both the mechanical strength and critical strength of threaded connections.