An apparatus for a gate valve between chambers includes a valve housing defining a flow path. A male valve portion is rotatable on a fixed axis in the housing. The male valve portion including a first male mating surface positioned at a first angle less than perpendicular to the axis. A female valve portion is fixed in the valve housing for receiving the male portion. The female valve portion including a first female mating surface positioned at a second angle matching the first angle. An o-ring seals the male valve portion to the female valve portion when the male valve portion is rotated into the female valve portion. A polished surface contacts the o-ring when the male valve portion is rotated. When the male valve portion is rotated into the female valve portion the o-ring is compressed thereby sealing the gate valve and closing the flow path.