A compact interaction chamber is used to cause high shear, impact forces, and cavitation to reduce particle size and mix fluids while reducing waste and holdup volume. A first housing made of stainless steel holds an inlet mixing chamber element and an outlet mixing chamber element in a female bore using thermal expansion. The inlet and outlet mixing chamber elements are manufactured so that the diameter of the cooled female bore is slightly smaller than the diameter of the mixing chamber elements. The first housing is heated, expanding the diameter of the female bore enough to allow the inlet and outlet mixing chamber elements to be inserted. After the mixing chamber elements are inserted and aligned within the female bore, the first housing is allowed to cool. Once cooled, the female bore contracts and applies sufficient hoop stress to securely hold the mixing chamber elements during high shear force mixing.