In the aerospace world, solid threaded inserts (Keenserts, Rosans, etc.) are always used when female threads are required in light alloys like aluminum or magnesium. The larger diameter of the insert’s OD thread gives a greater thread root shear area in the softer substrate material, and thus helps equalize the axial strengths of the hole and bolt.

Helicoils are not normally used in aerospace because the difference between its OD and ID are not large enough to improve the root shear capability much.