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Dimensional measurements

Diameter of plain setting rings and plugs

Internal diameter measurement of plain setting rings

We provide a UKAS accredited service for measuring the diameter of grade AA plain setting rings up to 250 mm in diameter to comply with the requirements specified in British Standard Specification 4064:1966 Plain setting rings for use with internal diameter measuring machines (Metric Units) or 4065:1966 (Inch Units). Certificates of calibration give the diameter at mid-bore, roundness at three specified positions and the variation of diameter along the bore.

Measurements of the diameter are made at three positions equi-spaced along the central half length of the bore in a single identified axial plane parallel with the supporting surface of the ring. The maximum variation of the three measured diameters is stated, together with the measured diameter at mid-bore. Diametral measurements and the assessment of the geometrical quality of the ring are confined to the central half-length of the bore.

Roundness measurements in accordance with British Standard Specification 3730:1983 Assessment of departure from roundness are made at three positions. The maximum departure from roundness and the measured departure from roundness at mid-bore, using the minimum zone criterion, are stated.

External diameter measurement of plain setting plugs

We provide a UKAS accredited service for measuring the diameter of plain setting plugs, pins, rollers and thread measuring cylinders in the range 0.1 mm to 150 mm diameter. 

The diameters of setting plugs are measured by comparison with calibrated gauge blocks of similar size. A plug is compared with a gauge block in a machine having flat, parallel measuring faces whose separation is determined either interferometrically or by using a capacitance gauging system. The measured size of the plug is corrected to zero measuring force. The diameter is measured midway along the length of the plug in a single identified plane and this result is stated together with the maximum variation in diameter obtained from diametral measurements made along and around the gauging surface. The departure from roundness (MZC) at the mid-axial position is measured and stated.

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