Cellular plastics and rubbers - Determination of linear dimensions
This standard is identical to the international standard ISO 1923-1981 Cellular plastics and rubbers - Determination of linear dimensions.
1 Subject content and applicable scope
This standard specifies the characteristics and the choice of the measuring equipment and procedure for determination of the linear dimensions of sheets, blocks or test specimens of cellular material (flexible and rigid).
This standard is applicable to the determination of linear dimensions of cellular plastics and rubbers.
2 Definitions
linear dimension: the shortest distance between two specific points, between two parallel lines or between two parallel planes, defined by corners, edges or surfaces of the cellular specimen
3 Measuring equipment
3.1 Dial gauge with a measuring surface of about 10cm2. The gauging pressure shall be 100±10Pa, and the reading accuracy shall be 0.05mm, as shown in Annex A.
3.2 Micrometer, having a measuring surface with a minimum diameter of 5mm, but in any case not less than 5 times the average diameter of the cells, permitting reading with an accuracy of 0.05mm.
Use of a micrometer is restricted to rigid cellular materials.
3.3 Sliding caliper, with a vernier permitting reading to an accuracy of 0.1mm.
3.4 Metal rule or metal tape, permitting reading to an accuracy of 0.5mm.
4 Procedure
The choice of measuring equipment shall be in accordance with the accuracy corresponding to the dimensions to be measured (see Table 1).
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Table 1 mm
Range of dimensions Required accuracy Instrument recommended Median of readings rounded off to the nearest millimetre
For normal use If the shape of the specimen permits
<10 0.05 Dial gauge or micrometer — 0.1
10~100 0.1 Sliding caliper Micrometer or dial gauge 0.2
>100 0.5 Metal rule or metal tape Sliding caliper 1
4.1.1 When an instrument accuracy of 0.05mm is required, a dial gauge or micrometer shall be used.
An accuracy of 0.05mm shall not normally be required for dimensions of more than 10mm.
4.1.2 When an instrument accuracy of 0.1mm is required, a sliding caliper shall be used.
This accuracy of 0.1mm shall not normally be required for dimensions of more than 100mm.
In this case, a dial gauge or micrometer may also be used, but then the instrument accuracy need not be better than that of a sliding caliper.
4.1.3 When an instrument accuracy of 0.5mm is required, a metal rule or metal tape shall be used.
In this case, a sliding caliper may also be used, but then the instrument accuracy need not be better than that of a metal rule or metal tape.
4.2 Number and location of the measurements
The number of the measuring locations depends on the size and the shape of the specimen, but shall be at least five. The locations shall be as widely separated as possible, in order to give a good average.
The median of three readings at each position shall be taken and the average of the five or more median values calculated.
4.3 Measurement with dial gauge
The measurement shall normally be made on a base plate. The base plate must be larger than the largest dimension of the specimen that is supported by the base plate. The specimen shall rest flat upon the base plate during the measurements.
The readings of the dial gauge shall be rounded off to the nearest 0.1mm.
4.4 Measurement with micrometer
For the measurement, the plane surfaces of the micrometer shall be continuously brought together until they just touch the cellular material, without causing any distortion or damage of the surface of the specimen. The specimen shall be moved slightly back and forward. Simultaneously the plane surfaces of the micrometer shall be slowly brought together until a slight resistance to the movement is felt.
The area of the measuring surface may be increased by measuring over metal sheet or plate.
The readings of the micrometer shall be rounded off to the nearest 0.1mm.
4.5 Measurement with sliding caliper
The readings of the sliding caliper shall be rounded off to the nearest 0.2mm.
The caliper shall be progressively preset to smaller measurements and presented to the specimen until the setting is reached when the caliper measuring faces just touch the surfaces of the specimen without any compression or damage to the latter.
4.6 Measurement with metal rule or metal tape
The cellular material shall not be distorted or damaged by the application of the metal rule or metal tape.
The metal rule or metal tape measurements shall be rounded off to the nearest 1mm.
1 Subject content and applicable scope
2 Definitions
3 Measuring equipment
4 Procedure
5 Test report
Annex A Dial gauge (Informative)
