While Part 1 covers how long or wide a part is, Part 2 covers its shape and relationship between features. It uses three tolerance classes:
One common mistake is assuming ISO 2768 applies to every single feature. It is important to remember that:Specific Trumps General: If a specific tolerance is written next to a dimension, that value overrides ISO 2768.Not for Plastics: ISO 2768 was originally designed for metal removal (machining) and sheet metal parts. For plastic injection molding, standards like ISO 20457 are often more appropriate.Check Your Material: Different materials react differently to heat and stress. Ensure the chosen tolerance class is achievable for the material you are using. Conclusion
Understanding ISO 2768: The Definitive Guide to General Tolerances for Linear and Angular Dimensions iso 2768 general tolerances pdf exclusive
Tolerance Values for Linear DimensionsThe allowable deviation depends on the size of the dimension. For example, in the Medium (m) class:For dimensions 0.5 to 3 mm, the tolerance is ±0.1 mm.For dimensions 30 to 120 mm, the tolerance is ±0.3 mm.For dimensions 400 to 1000 mm, the tolerance is ±0.8 mm.
In this example:"m" refers to the medium class for linear dimensions (Part 1)."k" refers to the medium class for geometrical tolerances (Part 2). Common Misconceptions and Best Practices While Part 1 covers how long or wide
Tolerance Values for External Radii and Chamfer HeightsThese are typically tighter to ensure fit and finish:For 0.5 to 3 mm, the tolerance is ±0.2 mm.Over 6 mm, the tolerance is ±0.5 mm. ISO 2768-2: Geometrical Tolerances
H (Highest precision)K (Medium precision)L (Lower precision) For plastic injection molding, standards like ISO 20457
Most general mechanical engineering applications utilize the "m" (medium) class.