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ISO 2768-1:1989(EN)General tolerances —
Part 1: Tolerances for linear and angular dimensions without individual tolerance indications
Technical Committee ISO/TC 3, Limits and Fits, created ISO 2768-1:1989 in 1989. The first edition, ISO 2768-1:1989, replaces and cancels ISO 2768: 1973 along with ISO 2768-2: 1989.
The following sections of ISO 2768 fall under the broad heading “General tolerances”:
— Part 1: Tolerances for linear and angular dimensions without individual tolerance indications
— Part 2: Geometrical tolerances for features without individual tolerance indications
Every feature on a component part has a size and a geometric shape. The function of the part involves constraints that, when surpassed, damage this function for deviations in size and deviations in geometrical characteristics (shape, orientation, and position).
Nothing should be suggested or left to discretion in the workshop or the inspection department; rather, the tolerance on the drawing should be complete to ensure that the elements of size and geometry of all features are regulated.
Making sure that this condition is met is made easier by using generic tolerances for size and geometry.
In order to make drawing indications simpler, ISO 2768-1:1989 establishes broad tolerances for angular and linear dimensions in four tolerance classes without providing specific tolerance indications.
It pertains to the dimensions of parts made from sheet metal or by the removal of metal from parts. These tolerances might be useful for non-metal materials as well. Parallel International Standards already exist or are being planned; for castings, see ISO 80621
Only the following dimensions, for which there is no individual tolerance indication, are covered by ISO 2768-1:1989:
a) linear dimensions, such as external sizes, internal sizes, step sizes, diameters, radii, distances, external radii, and chamfer heights for broken edges;
b) angular dimensions, such as right angles (90°), unless ISO 2768-2 is mentioned, or angles of uniform polygons; and
c) linear and angular dimensions produced by machining assembled parts.
It does not apply to the following measurements:
a) linear and angular measurements that are covered by other general tolerance standards;
b) auxiliary measurements shown in brackets; and
c) theoretically accurate measurements shown in rectangular frames.
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