Abstract: A valve with a calibrated flow orifice insert for use in Heating, Ventilation, and Air Conditioning (“HVAC”) applications so as to provide metered flow through the valve. The insert is used as a flow control device and is inserted into a conventional threaded ball valve. The insert has a cylindrical axial bore that is sized to provide a maximum valve flow coefficient. Peripheral threads on the insert mate with interior threads on the inlet of the valve body. A pair of bores on the face of the insert permit threaded insertion into the valve. The axial orifice bore through the insert is sized using experimentally-determined formulas related to the Reynolds numbers for the orifice and for the piping upstream of the insert.