Breviary Technical Ceramics






10.3.1 Tolerances and Function

Tolerances meeting the DIN 40 680 standard are based on application-dependent requirements and the conditions relative to different ceramic manufacturing procedures and materials when hard machining is not used.

To achieve higher dimensional, shape or position tolerances it is necessary to carry out some type of machining (e.g. grinding, lapping, polishing etc.) of the "as fired" component after firing. The tolerances that can be achieved in this way are specified in DIN ISO 2768 (general tolerances for workpieces produced with machining) and in DIN ISO 1101 (shape and position tolerances).
These are the standards usually applied in machine construction and related branches of industry.

For economic reasons it is always necessary to ensure that only those surfaces of ceramic components, typically functioning surfaces, are specified with close tolerances, and that general tolerances in accordance with DIN 40 680 apply to all other surfaces.

The dimensional tolerances described in DIN ISO 2768 are classified into fine, medium and coarse (g) categories, depending on the dimensions of the component. Tolerance classes for selected shape and position tolerances are also quoted ("H" for fine, "K" for medium and "L" for coarse). Requirements that exceeded these specifications, or different requirements for shape and position tolerances, are dealt with by DIN ISO 1101.

A corresponding specification of dimensional, shape or positional tolerances would, for instance, be

DIN ISO 2768-m-K or, for example, DIN ISO 2768-g-L

For further details see DIN ISO 2768 and DIN ISO 1101.

The manufacturers of technical ceramic components have specialised in particular materials and manufacturing processes. This permits them to manufacture economically, since the different material groups require entirely separate production lines and, in some cases, special equipment. Manufacturers who concentrate on components for machine construction are regularly confronted with close tolerances, for which reason they are usually equipped with machines suitable for hard machining.


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