Abstract: In a fixed head burner (13), which may be used in the manufacture of optical fibers and preforms for optical fibers, a machined quartz nozzle (10) is provided for insertion into a threaded aperture (14) of the fixed burner head (13), the quartz nozzle (10) being sized to provide sufficient space between the quartz nozzle (10) and the burner head (12) to allow for relative differences in thermal expansion and contraction to prevent stress fracture of the quartz nozzle (10). A seating surfaces (85) is machined on the quartz nozzle (10) for contact with a machined surface (90) of the burner head (12), and the quartz nozzle is held in place by a spring (18) placed behind the quartz nozzle (10), the spring (18) being held in place by a threaded end cap (24). The secure retention of the quartz nozzle (10) within an aperture (14) in the burner head (12) is further aided by the pneumatic pressure of gases applied to a rear surface (20) of the quartz nozzle (10).