Why does the strength of a scarf joint depend on the accuracy of the beveled surfaces?

The strength of a scarf joint is significantly influenced by the accuracy of the beveled surfaces because proper fitting of these surfaces directly affects the effective glue area. When the surfaces are accurately beveled, a larger area of wood is bonded together by adhesive, leading to a stronger connection between the two pieces. If the surfaces are poorly shaped or uneven, it results in a smaller area for glue adhesion, which compromises the joint's strength and stability. A well-fitted scarf joint distributes stress more evenly and reinforces the structural integrity of the assembly. This is critical in applications where the joint must withstand tension and shear forces.