AS B294-1970 pdf download.Plain setting rings for internal measuring equipment (inch series).
1 SCOPE. This standard relates to plain setting rings primarily intended for use in setting internal diameter measuring equipment.
The standard covers inch rings in the range from 0.08 in to 6 in, and provides for three grades of accuracy, viz, AA, A and B.
It specifies material for the rings, their hardness, surface texture and recommended overall dimensions (outside diameter and thickness).
2 MATERIAL REQUIREMENTS.
2.1 General. Setting rings shall preferably be made of good quality steel suitably hardened and stabilized and free from inclusions.
The measuring surface of a steel setting ring shall have a hardness value of not less than 780 I-IV or 62 HRC (after stabilizing).
Other materials may be used oniy if the setting rings produced have properties of hardness and stability at least equal to those specified for steel setting rings. Hardness shall be tested on the portion of the end face adjacent to the bore and shall be carried out in accordance with AS B84* or AS B106t.
2.2 Stabilizing. It is the responsibility of the manufacturer to ensure that setting rings are adequately stabilized by a method appropriate to their material.
NOTE: There are a number of suitable stabilizing processes, depending on type of steel. size and shape of product and required degree of stability: two suitable alternative stabilizing processes are as follows:
(a) Stabilizing by Low Temperature Tempering. The hardened setting rings, before final grinding, are heated to, and maintained at, a temperature of 150°C for a period of from 5 to 10 hours and allowed to cool slowly in the furnace.
(b) Stabilizing by Alternate Freezing and Low Temperature lempering. After hardcning and before the final grinding, the setting rings should be submitted to at least two cycles of freezing (down to a suitable temperature in the range between —50°C to —l 20°C) and tempering at +150°C.
The last operation should be tempering with slow cooling to the surrounding atmospheric temperature.
3 GENERAL FEATURES OF DESIGN.
3.1 Recommended Dimensions. The recom mended outside diameters and lengths (see Fig. 1) for setting rings are given in Table 1.AS B294-1970 pdf download.