ISO 2768m is a standard that specifies general tolerances for linear and angular dimensions without individual tolerance indications. It is intended to simplify drawing indications and design of machining parts. It applies to four tolerance classes: f (fine), m (medium), c (coarse), and v (very coarse).
ISO 2768m is part of ISO 2768, which consists of two parts: ISO 2768-1 (Tolerances for linear and angular dimensions) and ISO 2768-2 (Geometrical tolerances for features). The m class is specified in ISO 2768-1, while the other classes are specified in ISO 2768-2.
ISO 2768m provides permissible deviations for linear dimensions such as external sizes, internal sizes, step sizes, diameters, radii, distances, external radii, and chamfer heights for broken edges. It also provides permissible deviations for angular dimensions, including right angles and angles of uniform polygons.
To download the PDF of ISO 2768m, you can visit the official website of ISO or some other websites that provide the PDF file. Here are some examples:
ISO 2768 1 & 2 - ISO General Tolerances Chart (PDF) - DEK
General Tolerances for Linear and Angular Dimensions - ISO 2768 Tolerance Chart & PDF CNCLATHING
General Tolerances to DIN ISO 2768 - DAU Components
Before downloading the PDF, make sure you have a compatible software to open and view it. You can also check the latest version and revision date of the standard to ensure its accuracy and validity.
ISO 2768m is useful for simplifying the drawing and design process of machining parts. It reduces the need for individual tolerance indications and allows for a uniform application of tolerances. It also helps to avoid unnecessary precision and cost, as well as to ensure the interchangeability and functionality of parts.
However, ISO 2768m is not applicable for all dimensions and features. It does not cover dimensions that are covered by other standards on general tolerances, auxiliary dimensions indicated in brackets, or theoretically exact dimensions indicated in rectangular frames. It also does not apply to materials other than metal, unless otherwise specified.
Therefore, when using ISO 2768m, it is important to consider the production capacity of the manufacturer and the requirements of the parts to be made. The tolerance class should be chosen according to the customary workshop accuracy and the design needs. Smaller or larger tolerances should be indicated adjacent to the relevant nominal dimensions.
To illustrate how ISO 2768m works, let's take an example of a part with a linear dimension of 50 mm and an angular dimension of 90Â. If we want to apply the m class tolerance to this part, we can refer to the tables in ISO 2768-1 and find the permissible deviations for these dimensions. According to the tables, the linear dimension has a deviation of Â0.2 mm and the angular dimension has a deviation of Â1Â. This means that the actual size of the part can vary from 49.8 mm to 50.2 mm and the actual angle can vary from 89Â to 91Â.
If we want to apply a different tolerance class, such as c or v, we can refer to the tables in ISO 2768-2 and find the permissible deviations for these classes. According to the tables, the linear dimension has a deviation of Â0.5 mm for c class and Â1.0 mm for v class, while the angular dimension has a deviation of Â1Â30' for c class and Â3Â for v class. This means that the actual size of the part can vary from 49.5 mm to 50.5 mm for c class and from 49 mm to 51 mm for v class, and the actual angle can vary from 88Â30' to 91Â30' for c class and from 87Â to 93Â for v class.
As you can see, different tolerance classes have different effects on the accuracy and quality of the part. Therefore, it is important to choose the appropriate tolerance class according to the design specifications and manufacturing capabilities. 29c81ba772