Machined parts must be straight, have parallel and square edges, and surfaces of good quality. Improperly machined components may result in cupped panels and joint failure. Improperly maintained or adjusted machinery may result in components with non-parallel edges. Non-parallel edges result in uneven glue spread and pressure. If the piece is machined properly, the width of the component should measure the same in the middle and at each end.
Any deviation is compounded as faulty components are assembled.
A severe form of non-parallel edges is snipe. Snipe occurs when more wood is removed from one edge of a piece due to a deviation as the saw blade enters the piece, or the piece does not meet a cutter head on a level plane. Figure 1 illustrates snipe and how it affects panel quality. It is also important that the edges are machined square. When edges are not square, a gap occurs along one edge of the glue line.