BS ISO 48:2007 pdf free.Rubber, vulcanized orthermoplastic — Determination ofhardness (hardnessbetween 10 IRHD and100 IRHD).
BS ISO 48 standard hardness hardness, reported to the nearest whole number in international rubber hardness degrees, obtained using theprocedures described in methods N, H, L and M on test pieces of the standard thickness and not less than theminimum lateral dimensions specified.
apparent hardness hardness, reported to the nearest whole number in international rubber hardness degrees, obtained using theprocedures described in methods N, H,L and M on test pieces of non-standard dimensions, as well ashardness values obtained using methods CN, CH, CL and CM.
NOTE Values obtained by methods CN, CH, CL and CM are always given as apparent hardnesses since tests arecommonly made on the complete article where the thickness of the rubber may vary and, in many cases, the lateraldimensions may not provide the minimum distance between the indentor and the edge necessary to eliminate edgeeffects. Thus the readings obtained do not in general coincide with readings obtained on standard test pieces as defined inmethods N, H, L and M or on a flat parallel-faced slab of the same thickness as the article.Moreover, the readings maydepend appreciably on the method of support of the article and whether or not a presser foot is used.It should, therefore,be recognized that results obtained on curved surfaces are arbitrary values applicable only to test pieces or articles of oneparticular shape and of particular dimensions, and supported in one particular way, and in extreme cases such values maydiffer from the standard hardness by as much as 10 IRHD.Furthermore, surfaces that have been buffed or otherwiseprepared to remove cloth markings,etc., may give slightly different hardness values from those with a smooth, mouldedfinish.
The hardness test consists in measuring the difference between the depths of indentation of a ball into therubber under a small contact force and a large (indenting) force. From this difference, multiplied when usingthe microtest by the scale factor 6, the hardness in international rubber hardness degrees (IRHD) is obtainedfrom Tables 3 to 5 or from graphs based on these tables or from a scale, reading directly in internationalrubber hardness degrees, calculated from the tables and fitted to the indentation-measuring instrument. Thesetables and curves are derived from the empirical relationship between indentation depth and hardness givenin Annex A.BS ISO 48 pdf download.