3.10 SUMMARY

Rigid integral mechanical attachments or rigid interlocks are those types that remain rigid throughout the engagement, locking, and retention in service stages of assembly. By remaining rigid, they have to be designed such that the geometric profile of one part (called the "mating part" when it is the one being added) will cause interference with the profile of another part (called the "base part," as it is normally held fixed while the mating part is added), with externally-applied and internally-generated loads carried by bearing of one against the other. Loads in the parts can be tension, compression, or shear from tension, compression, bending, or torsion.

Rigid interlocks can be classified based on the way the overall joint or actual attachment features creating the joint are intended to operate or, alternatively, by the method by which the actual attachment features are created. Within the former scheme of classification, there are: (1) completely rigid joints; (2) integral locking features; (3) embedded rigid fasteners; (4) integral rigid attachment features; and (5) rigid couplings and connectors. There is also a special sub-class known as "rigid locators" that are used in integral elastic snap-fit assembly together with the elastic locking feature(s). Within the latter classification scheme, there are rigid interlocking features that are designed (and fabricated) in the joint elements or parts, permanently added to the joint elements, temporarily added to the joint elements, or detachable or easily removable features of joint elements.

Rigid interlocks can be found that are suitable...