Guide To General Tolerance – ISO 2768 1&2 Standard

There are a large number of spare metal or plastic parts will be designed and manufactured every day. If there is no tolerance standard to manage the dimensional of products, the designers and mechanics will be crazy, because it will add a lot of difficult work. In order to simplify the design and production of Machinists, the international tolerance organization has developed and issued this international tolerance standard, which can be used for machining, cutting, and other parts.

In this article, we will introduce ISO 2768 in detail. At the same time, we have prepared the latest revision PDF of ISO 2768 for download.

What is ISO 2768?

ISO 2768 is an International Standard that created by the International Organization for Standardization (ISO), it is intended to simplify drawing specifications for mechanical tolerances. Its creation and implementation make design and production more convenient, and make cooperation between different companies easier and closer.

International Standard ISO 2768:1989 was prepared by Technical Committee ISO/TC 3, Limits, and fits, it comes in two parts, namely ISO 2768-1 and ISO 2768-2.

• Part 1 – General Tolerances for linear and angular dimensions.
• Part 2 – Geometrical tolerances for features.

ISO 2768 mainly applies to parts manufactured by machining or material removal. For part sizes without marked tolerance ranges, this standard should be followed. Please note that all tolerance limits are given in mm.

Part 1: General Tolerances ISO 2768-1

ISO 2768-1 is intended to simplify drawing indications and specifies general tolerances in 4 tolerance classes (f – fine, m – medium, c – coarse, v – very coarse). It applies for the linear dimensions and angular dimensions such as external sizes, internal sizes, step sizes, diameters, radii, distances, external radii, and chamfer heights for broken edges.

If general tolerances in accordance with ISO 2768 shall apply, ISO 2768 followed by the tolerance class (Ex: ISO 2768-m) shall be indicated in or near the title block.

The following is the tolerance table corresponding to the 4 class precision levels, you can choose the most suitable one according to machining capabilities and your design requirements.

Table 1 – Linear Dimensions

For nominal sizes below 0.5 mm, the deviations shall be indicated adjacent to the relevant nominal size(s).

Table 2 – External Radii and Chamfer Heights

For nominal sizes below 0.5 mm, the deviations shall be indicated adjacent to the relevant nominal size(s).

Table 3 – Angular Dimensions

Table 3 – Angular Dimensions

Part 2. General Tolerances ISO 2768-2

ISO 2768-2 is for simplifying drawing and fixes general tolerances in 3 tolerance classes (H, K, and L), this part including General Geometrical Tolerances range of flatness & straightness, cylindricity, and circularity. You can check the tolerance chart below:

Table 4 – General Tolerances on Straightness and Flatness

Таблица 5 – Общие допуски перпендикулярности

Таблица 6 – Общие допуски симметричности

Таблица 7 – Общие допуски радиального биения

Часто задаваемые вопросы

Последняя редакция ISO 2768 в формате PDF

• ISO 2768 1&2 (PDF, EN, 107 КБ)

Резюме

Подводя итог, можно сказать, что допуски — очень важная и неотъемлемая часть проектирования изделий. Стандарт ISO 2768 определяет значения общих допусков, что значительно упрощает проектирование и производство. Благодаря этому стандарту мы можем более эффективно взаимодействовать, экономить время и затраты.

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