A resonant apparatus such as a resonant waveguide module in an RF particle accelerator includes an unbrazed joint that provides a reliable vacuum seal and RF contact between resonators with precisely controlled internal geometry. The joint can be disassembled and reassembled without degradation. Hard, stainless steel end faces include knife edges pressed into a copper central component, such as a gasket. The knife edges extend the waveguide interiors without gaps or interruptions. The central component serves as a coupling iris or other functional component of the resonant apparatus, thereby allowing the central component to have substantial dimensions that inhibit mechanical distortions thereof. The waveguides and knife edges can be copper plated. Embodiments include embedded passages and/or recesses used for cooling, radiation shielding, magnetic focusing coils, and/or electron optics element formed by permanent magnets.