Drilling operations; parts and assemblies

A carpentry product consists of parts and assemblies. A part is made without assembly operations, for example a glued bar made to a drawing or multi-layer plywood. An assembly is a built-up item whose components are joined by fastening, gluing or other assembly. An assembly with no other assemblies inside is simple (for example a chair frame glued from legs and stretchers); one that contains other assemblies is complex (a cabinet drawer). A chair’s back, seat and leg stretchers are its parts; a cabinet’s walls, doors, lids and shelves are its main elements. The wide side of a bar is called the face and the narrow side the edge. A surface cut at a right angle to the grain is the end face, one cut at another angle is the half-end face, and the slanted cut on a sharp edge is a bevel, which makes the material more resistant to outside forces. Cutting wood fibres in an arbitrary direction weakens a part, so a chair’s back legs are designed so that few fibres are cut. It is good when the grain follows the length of the part. Wood changes shape differently in radial and tangential directions as moisture changes, so parts are laid out allowing for this.