Abstract: A bar stock feed tube assembly is disclosed of the type in which bar feed stock is supported and guided by, and rotates within, the assembly during machining. The feed tube assembly is comprised of an anechoic feed tube, a surrounding reinforcing jacket, and an intermediate, acoustically-decoupling layer of energy-absorbing material. Retaining caps are provided at the ends of the assembly to protect the end of the anechoic feed tube and its jacket, to act as a stop against axial movement of the assembly, and to retain the feed tube within the reinforcing jacket. By utilizing retaining caps having feed stock-receiving orifices of smaller diameters than the feed tube, the assembly may be adapted for use with a wide range of bar stock sizes.