Abstract: An expandable tap hole plug includes a plug comprising a cylindrical member having a circular nose and an outwardly extending flexible sidewall forming a variable obtuse angle with respect to the nose. The plug is adatepd to be oriented within a tap hole of a metallurgical vessel with the nose directed towards the interior of the vessel. An expander, in the form of a truncated cone, has a base and spokes extending outwardly from the base forming a variable obtuse angle with respect to the base. The expander is inverted relative to the plug and is attached to the plug with the spokes of the expander engaging the sidewall of the plug. The angle between the side section and base of the expander is varied so as to vary the angle of the sidewall of the plug relative to the nose thereof to block the tap hole.