Abstract: An industrial stud welding machine is provided with a chuck which defines a work piece receiving orifice of infinitely variable diameter. The stud welding chuck is thereby able to accommodate studs of different diameters, and is also adjustable to compensate for wear resulting from extended use. The stud welding chuck employs a barrel having an annular wall in which longitudinal slots are defined. The barrel is tapered and threaded externally. A collet encircles the barrel and is treadably engaged therewith. Advancement of the collet in one longitudinal direction squeezes the edges of the barrel walls together to reduce the work piece receiving orifice diameter. Advancement of the collet in the opposite direction along the barrel allows the work piece receiving orifice to open to a larger diameter.