Breviary Technical Ceramics



 Hard Machined Ceramic

For parts made of technical ceramics for machine construction applications, the tolerances mentioned above for functional surfaces are often inadequate for the user's needs. For this reason, tolerances for ceramic parts in accordance with

DIN ISO 2768-m-K

are quoted. These can be achieved through hard machining.

Drawing specifications

Dimensional tolerances that do not correspond to the general tolerances according to this standard are to be listed according to DIN 40 680-1 and -2 as tolerances or as ISO tolerance zones, directly stating the appropriate nominal dimension.

General tolerances with symmetrical dimensions with accuracy grades "medium" and "coarse" according to tables 29 and 30 are not added directly to the nominal dimensions. Instead, the following entries are made in the title block:

DIN 40 680-A-m or
DIN 40 680-A-g.

If several ceramic parts are shown on a single drawing, and if those parts are produced using different processes and therefore possess general tolerances with different grades of precision as specified by DIN 40 680-1, then the coarsest precision grade is entered into the title block. The tolerances with the finer precision grade are then added to the corresponding nominal dimension.
It can happen that for reasons of function, or for reasons concerned with production techniques, either only positive or only negative tolerance dimensions can be shown, but that the tolerance range is nevertheless intended to correspond to one of the particular precision grades in the general tolerances according to tables 29/30. In such cases, the figure for the associated general tolerance is doubled where the relevant nominal dimension is stated, and simply given an arithmetic sign. These tolerances, however, are not considered general tolerances, and are thus added to the corresponding nominal dimension rather than being entered into the title block.
Since the general tolerances for the "fine" accuracy grade are not fixed, either the tolerance agreed between the user and the manufacturer or the ISO tolerances are always added after the nominal dimension.
For further details, see DIN 40 680-1.

Table 29: Manufacturing procedures for dimensional tolerances in accordance
with DIN 40 680-1 for the "coarse" and " fine" precision grades

Table 30: General tolerances for products without finishing after firing

<< back   home   next >>