A waveguide interface for millimeter wave and sub-millimeter wave applications adapted to couple and uncouple abutting waveguide sections wherein said waveguide interface acts as both a mating surface and a precision alignment mechanism. The waveguide interface comprises a first member having a first waveguide defined therein, a second member having a second waveguide similar in cross-section to said first waveguide defined therein, a means for mating said first member and said second member comprising a centrally located precision mating surface through which propagates electromagnetic energy and additionally comprising at least one pair of diametrically opposed rotational alignment pins and holes located a specified distance from said centrally located precision-mating surface, and wherein said pins and holes are in mating relation of looser fitment than said centrally located precision mating surface.