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ONORM EN 237:2005
Liquid petroleum products - Petrol - Determination of low lead concentrations by atomic absorption spectrometry (Austrian Standard)
Applies to reamers, screwing taps, etc. It comprise two series of dimensions. The complete range of diameters is divided into a certain number of diameter steps. In the metric tables, the values of the across flats of the squares and the preferred diameters are scaled in accordance with the R20 series of preferred numbers. In the inch tables, these values are exact conversions of the corresponding metric values.
Austrian Standards Institute [on]