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Finish/flatness concepts
The surfaces produced by machining and other methods of manufacturing are generally irregular and complex. Of practical importance are the geometric irregularities generated by the machining method. These are defined by the height, width, direction and other random characteristics not of geometric nature.
The general term applied to define these terms is surface texture, the repetive or random deviation from the nominal surface (Figure 3) which forms the pattern of the surface. It includes roughness, waviness, and lay.
- Roughness consists of fine irregularities in the surface texture produced by the machining process. (figure 4)
- Waviness is the widely spaced component of surface texture. It is of wider spacing than roughness. (Figure 4) It results from cutting tool deflection and run out.
- Lay is the direction of the predominate surface pattern and is determined by the machining process used in producing the surface. (Figure 4)
Measuring Flatness
Our diamond laps produce flatness to within one light band (11.6 millionths of an inch) on an 1.5" diameter disc and surface finishes to within one micro inch. Which is easily read by using an optical flat. The flatness of our lapping plate is transferred to your work piece, so little lapping experience is required to use our lapping plate, providing you with automatic repeatability and control.
In surface texture and flatness millionths of an inch are quoted. These extremely small distances introduce possible problems which must be considered in finishing operations. Flatness is commonly measured by the use of optical flats. Fringe bands appear from interference in the monochromatic light rays used. Curvature of bands show the degree of flatness. The smount by which the bands curve and/or their spacing constitute the scale used in measuring flatness. One full band is equal to 11.6 millionths of an inch.
