ISO 286-2:2010 pdf free download.Geometrical product specifications (GPS) — ISO code system for tolerances on linear sizes — Part 2: Tables of standard tolerance classes and limit deviations for holes and shafts.
This part of ISO 286 is a geometrical product specification(GPS)standard and is to be regarded as a general GPS standard (see ISO/TR 14638 ).It influences chain links 1 and 2 of the chain of standards on size in the general GPS matrix.
For more detailed information on the relationship of this part of ISO 286 to the GPS matrix model, see Annex B.
The need for limits and fits for machined workpieces was brought about mainly by the requirement for interchangeability between mass-produced parts and the inherent inaccuracy of manufacturing methods coupled with the fact that”exactness “of size was found to be unnecessary for most workpiece features. In order that the fit function could be satisfied, it was found sufficient to manufacture a given workpiece so that its size lay within two permissible limits, i.e. a tolerance, this being the variation in size acceptable in manufacture while ensuring the functional fit requirements of the product.
Similarly, where a specific fit condition is required between mating features of two different workpieces, it is necessary to ascribe an allowance, either positive or negative, to the nominal size to achieve the required clearance or interference. ISO 286 gives the internationally accepted code system for tolerances on linea sizes. It provides a system of tolerances and deviations suitable for two types of feature: cylinder and”two parallel opposite surfaces. The main intention of this code system is the fulfilment of the function fit.
The terms “hole, “shaft and”diameter are used to designate the types of feature of cylinders(e.g. for tolerancing of the diameter of a hole or shaft ). For simplicity, they are also used for two parallel opposite surfaces(e.g. for the tolerancing of the thickness of a key or the width of a slot).
The pre-condition for the application of the ISO code system for tolerances on linear sizes for the features forming a fit is that the nominal sizes of the hole and the shaft are identical.
The previous edition of ISO 286-2(published in 1988) had the envelope criterion as the default association criterion for the size of a feature; however, ISO 14405-1 changes this default association criterion to the two- point size criterion. This means that form is no longer controlled by the default specification of size.
In many cases, the diameter tolerances specified in this part of ISO 286 are not sufficient for effective control of the intended function of the fit. The envelope criterion specified in ISO 14405-1 may be required. In addition, the use of geometrical form tolerances and surface texture requirements may improve the control of the intended function.
A general graphical representation of the relationship between the respective tolerance classes and thei deviations is given in Annex A.
ISO 286-2:2010 gives values of the limit deviations for commonly used tolerance classes for holes and shafts calculated from the tables given in ISO 286‑1. ISO 286-2 covers values for the upper limit deviations eU, hole (for holes) and eU, shaft (for shafts) and the lower limit deviations eL, hole (for holes) and eL, shaft (for shafts).