What do International Standards say about flatness? In its early drafts, ISO 12781-2 proposed the use of a 0.8 mm cutoff wavelength to remove short wavelengths (i.e. roughness) from flatness. This 0.8 mm value was chosen since it is the most common surface roughness cutoff wavelength.
For parts under 36” in both width and length, flatness should not exceed ¼”. For parts whose length is between 36” and 72”, the flatness variation should not exceed 75% of the flatness of a 10' sheet for that given width.
ISO flatness and how it is calculated
The ISO 1101 standard defines, that the distance between two parallel planes must be as small as possible while including all measurement points.
Flatness is a GD&T form tolerance that is conceptually simple. According to the ASME Y14. 5 standard, it “specifies a tolerance zone defined by two parallel planes within which the surface must lie.” Figure 1 illustrates this concept very well.
The deviations in flatness are often measured in values of waves (λ), which are multiples of the wavelength of the testing source. One fringe corresponds to ½ of a wave. 1λ flatness is considered typical grade, λ/4 flatness is considered to be precision grade, and λ/20 is considered high precision grade.
In theory, perfect flatness can be defined as a surface that has no deviation from a perfect plane.
MZ Flatness Definition
Flatness can also be analysed by a minimum zone calculation, defined as two parallel planes that totally enclose the data and are kept to a minimum separation. The flatness error can be defined as the separation of the two planes.
A flat surface has no high points or low points, and is completely even. Flatness is typically measured using a surface plate, which is a large, flat piece of granite or cast iron. A surface plate is used as a reference surface, against which the flatness of a part can be measured.
The ASME Y14. 5 Dimensioning and Tolerancing Standard is considered as the authoritative guideline for the design language of geometric dimensioning and tolerancing (GD&T) and is essential in ensuring that drawing information and symbols are being interpreted and communicated properly.
ASME B31Q specifies the requirements for identifying covered tasks that impact the safety or integrity of pipelines, for qualifying individuals to perform those tasks, and for managing the qualifications of pipeline personnel.
Floor flatness and levelness reporting
The specification should provide the equivalent minimum local values, which are normally 60% of these values, or 15.0 and 12.0, respectively.
Using a Dial Gauge
Set the dial gauge so that its measuring part comes into contact with the measurement surface. Move the target so that the measurement surface is evenly measured, and read the dial gauge values. The largest deviation value is the flatness.
ACI PRC-117.1R-14 defines floor flatness (Ff) as “deviation of a surface from a plane” and floor levelness (Fl) as “deviation of a line or surface from a horizontal line or surface.” Flat floors make it easier to maintain tolerances in manufactured products such as airplane wings.
The flatness tolerance zone is two parallel planes 0.1 mm apart. The size can never be greater than 31 or less than 29. Note below that when the part is created at size 31, the form must be perfect per rule #1. Therefore the tolerance zone has its top plane at 31 and its bottom plane at 30.9.
I-Units is an exacting quantitative flatness measurement. It is a dimensionless number that incorporates both the height (H) and peak to peak length (L, or P in the diagram below) of a repeating wave. For example: a sheet with a 1/16” high wave which repeats every 12” would have an I-Unit value of 6.7.
NSF/ANSI 14 establishes minimum physical, performance, health effects, quality assurance, marking and recordkeeping requirements for thermoplastic and thermoset plastic piping system components, including but not limited to pipes, fittings, valves, joining materials, gaskets and appurtenances.
Y14. 46 is intended to support engineers engaged in Additive Manufacturing – including mechanical design, drafting, and quality assurance & control personnel – especially those involved in extended, global supply chains. ASME helps the global engineering community develop solutions to real world challenges.
The ASME A17. 1 code addresses features of required two-way emergency communication devices, including controls and visual indicators. The ABA Standards apply requirements for operable parts and tactile characters and symbols.
The flatness tolerance zone is the area between two parallel planes, into which the surface in question would need to fit in order to qualify as “flat.” The flatness tolerance would be the allowable distance between those parallel planes.
Floor Flatness is measured by tracking the difference in elevation between two points 1 foot apart and comparing them with every other 1-foot elevation change across a measured distance or “run.” Floor Levelness on the other hand compares the change in elevation over a distance of 10 feet, by determining the net change ...
a The degree of flatness is defined as η = (D0 − D)/D0, where D and D0 are the diameters of the native and the deformed tubes, respectively. A quarter of the SWCNT surface was divided into the flattened and edged regions by the flattened, middle, and edged lines.
To measure flatness, the part being measured is placed on the surface plate and a dial indicator is used to measure the distance between the part and the surface plate at various points. The readings are taken at different locations across the surface of the part to ensure that it is uniformly flat.
The Maple Flooring Manufacturers Association (MFMA) requires the general contractor to provide a concrete slab troweled smooth and flat to a tolerance of 1/8" in a 10' radius, subject to the approval of the MFMA Sport Floor Contractor.
Surface flatness is a type of surface accuracy specification that measures the deviation of a flat surface such as that of a mirror, window, prism, or plano-lens.