A surgical assembly for kinematically coupling two surgical components is provided. The surgical assembly includes a first surgical component having a receiver, which defines a cavity and has a plurality of constraint surfaces accessible in the cavity. The surgical assembly further includes second surgical component having a key, which has a triplicity of kinematic elements to repeatably position the key in the receiver. The surgical assembly further includes a preloading mechanism having a load member arranged to secure the key in the receiver such that the kinematic elements contact the receiver at the plurality of constraint surfaces such that the key is kinematically constrained to the receiver by being constrained by six points of contact with the receiver.