From Surfaces and their Measurements

10.1 General statement

One of the biggest problems of form is concerned with one of its boundaries i.e. waviness. Waviness is difficult to deal with from a purely geometric standpoint. It is not a measure of a metal-air boundary as is roughness. Neither is it a deviation from a perfect Euclidean shape as are the measurements of the deviations from straightness, flatness and roundness (Figures 10.1 and 10.2). At least, in these latter cases, there is some defined perfection. (The definition can be written down formally.) This makes the measurement problem easier. On the other hand, the wide range of different engineering shapes that have to be contended with is considerable. Some general classification will be discussed in what follows.


Figure 10.1: Relationship between roughness, waviness, and form

Figure 10.2: Quality regimes for surface geometry

To be consistent with what has already been said, deviations from, or concerned with, a linear variable will be considered in this chapter. Form can be considered to extend into straightness and then flatness. Geometric shapes concerned with curves such as circles, epi-trochoids etc. are examined later in Section 11.

Errors of form suffer from the opposite of roughness. In roughness, the short wavelengths are known to be subject to instrumental constraints such as stylus dimension. It is the long-wavelength boundary of waviness that is difficult to define. This is the short wavelength boundary of form. In form errors, the long wavelengths are determined by the ideal shape specified e.g. a circle and it is...

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Products & Services
Form Gages and Form Gaging Systems
Form gages and form gaging systems are used to inspect parameters such as roundness, angularity, squareness, straightness, flatness, runout, taper and concentricity. 
Surface Metrology Equipment
Surface metrology equipment is used to measure the surface finish and/or geometry of engineering components. Surface texture and topology characteristics include surface roughness, contour, form, waviness, and defects.
Surface Profilometers
Surface profilometers are contact or non-contact instruments used to measures surface profiles, roughness, waviness and other finish parameters.
Styli and Probes
Styli and probes are slender, rod-shaped stems and contact tips or points used to probe surfaces in conjunction with profilometers, SPMs, CMMs, gages and dimensional scanners.
Color Meters and Appearance Instruments
Color meters and appearance instruments are used to measure the properties of paints and coatings including color, gloss, haze and transparency.

Topics of Interest

11.1 General (See ISO 6318 1985 for terminology, 14291 for properties) So far, deviations from ideal shapes, which are linear or substantially so, can be related to a straight generator. There are,...

18.10 Separation from roughness and waviness The separation of roughness and waviness from geometrical deviations (form, orientation, location, run-out) is not yet completely internationally...

8.3 Surface Properties of Ceramics The surface properties of interest, surface roughness and camber, are highly dependent on the particle size and method of processing. Surface roughness is a measure...

Mass finishing typically smoothes external surfaces and cleans them at the same time it removes burrs. Because they combine part improvement attributes mass finishing processes are exceptionally...

Every part's surface is made up of texture and roughness which varies due to manufacturing techniques and the part structure itself. To understand a component's surface and to control the...