Surface Finish Imperfections Form Error Form error encompasses the long wavelength deviations of a surface from the corresponding nominal surface. Form errors result from large scale problems in the manufacturing process such as errors in machine tool ways, guides, or spindles, insecure clamping, inaccurate alignment of a workpiece, or uneven wear in machining equipment. Form error is on the dividing line in size scale between geometric errors and finish errors. Texture Surface texture is the combination of fairly short wavelength deviations of a si4rface from the nominal surface. Texture includes roughness, waviness, and lay, that is, all of the deviations that are shorter in wavelength than form error deviations.
Surface texture includes roughness and waviness.
Roughness generally results from a particular production process or material condition. Waviness errors are intermediate in wavelength between roughness and form error. Note that the distinction between waviness and form error is not always made in practice, and it is not always clear how to make it. New standards are emerging that define this distinction more rigorously as developed in later sections. Lay Lay refers to the predominant direction of the surface texture.