1、CEN EN*k227b8-2 93 m 3404589 004b963 537 m EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 22768-2 April 1993 UDC 621.713.14 : 744.4 Descriptors: Machine components, geometrical tolerances, machinhg tolerances, dimensional deviations, specifications English version General tolerances - Part 2 :
2、 Geometrical tolerances for features without individual tolerance indications (IS0 2768-2 : 1989) lblrances gnrales - Partie 2 : lblrances gomtriques pour lments non affects de tolrances individuelles lbleranzeintragung Allgemeintoleranzen - Teil 2 : Toleranzen fr Form und Lage ohne einzelne (IS0 27
3、68-2 : 1989) (IS0 2768-2 : 1989) This European Standard was approved by CEN on 1993-04-15. CEN members are bound to comply with the CENKENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date li
4、sts and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the resp
5、onsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norwa
6、y, Portugal, Spain, Sweden, Switzerland and United Kingdom. CEN European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels O 1993 Copyright reserved to CEN members Ref. No. EN 22768-2 : 1993 E CEN EN*2
7、2768-2 93 m 3404589 0046964 473 m Page 2 EN 22768-2 : 1993 Foreword In 1991, the International Standard IS0 2768-2 : 1989 Geneml tolemnces - Frt 2 : Geomet.mcal tolerances for features wht individual tolerance indications was submitted to the CEN Primary Questionnaire Procedure. Following the positi
8、ve result of the CEN/CS proposal, IS0 2768-2 : 1989 was submitted to the formal vote. The result of the Formal Vote was positive. This European Standard shaii be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by October 1993, and
9、conflicting national standards shall be withdrawn at the latest by October 1993. In accordance with the CENKENELEC Internal Regulations, the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxemb
10、ourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, United Kingdom. NOTE. The European references to international publications are given in annex ZA (normative). CEN ENx227bB-2 93 3404589 004bb5 30T W page 3 EN 22768-2 : 1993 Introduction All features on component parts always have a s
11、ize and a geometrical shape. For the deviation of sire and for the deviations of the geometrical characteristics (form, orientation and location) the function of the part requires limitations which, when exceeded, impair this function. The tolerancing on the drawing should be complete to ensure that
12、 the elements of size and geometry of all features are controlled, .e. nothing shall be implied or left to judge- ment in the workshop or in the inspection department. The use of general tolerances for size and geometry simplifies the task of ensuring that this prerequisite is met. CEN EN*227b8-2 73
13、 = 3404587 004b7bb 24b Page 4 EN 22768-2 : 1993 General tolerances - Part 2: Geometrical tolerances for features without individua tolerance indications 1 Scope This part of IS0 2768 is intended to simplify drawing indica- tions and specifies general geometrical tolerances to control those features
14、on the drawing which have no respective in- dividual indication. It specifies general geometrical tolerances in three tolerance classes. This part of IS0 2768 mainly applies to features which are pro- duced by removal of material. Its application to features manufactured by other processes is possib
15、le; however, special examination is required to ascertain whether the customary workshop accuracy lies within the general geometrical toler- ances specified in this part of IS0 2768. 2 General When selecting the tolerance class, the respective customary workshop accuracy has to be taken into conside
16、ration. If smaller geometrical tolerances are required or larger geometrical tolerances are permissible and more economical for any individual feature, such tolerances should be indicated directly in accordance with IS0 1101 (see clause A.2). General geometrical tolerances in accordance with this pa
17、rt of IS0 2768 apply when drawings or associated specifications refer to this part of IS0 2768 in accordance with clause 6. They apply to features which do not have respective individual geometrical tolerance indications. General geometrical tolerances apply to all geometrical toler- ance characteri
18、stics, excluding cylindricity, profile of any line, profile of any surface, angularity, coaxiality, positional toler- ances and total run-out. In any event, general geometrical tolerances in accordance with this part of IS0 2768 should be used when the fundamental tolerancing principle in accordance
19、 with IS0 8015 is used and indicated on the drawing (see clause B.1). 3 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this part of ISO2768. At the time of publication, the editions indicated were valid. All standards a
20、r3 subject to revision, and parties to agreements based on this part of IS0 26 are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and IS0 maintain registem of currently valid International Standards. IS0 1101 : 1983, Te
21、chnical drawings - Geometrical toleranc- ing - Tolerancing of form, orientation, location and run-out - Generalities, definitions, symbols, indications on drawings. IS0 2768-1 : 1989, General tolerances - Pert 1 : Tolerances for linear and angular dimnsions without individual tolerance indi- cations
22、. IS0 5459 : 1981, Technical drawings - Geometrical toleranc- ing - Datums and datumsystems for geometrical tolerances. IS0 8015 : 1985, Technical drawings - Fundamental toleranc- ing principle. 4 Definitions For the purposes of this part of IS0 2768, the definitions for geometrical tolerances given
23、 in IS0 1101 and IS0 5459 apply. 5 General geometrical tolerances (see also clause B. 1) 5.1 Tolerances for single features 5.1.1 Straightness and flatness The general tolerances on straightness and flatness are given in table 1. When a tolerance is selected from table 1, it shall be based, in the c
24、ase of straightness, on the length of the cor- responding line and, in the case of Ratness, on the longer lateral length of the surface, or the diameter of the circular sur- face. CEN ENlit22768-2 93 3404589 O046967 182 Page 6 EN 22768-2 : 1993 Table 1 - General tolerances on straightness and flatne
25、ss Values in millimetres Straightness and flatness tolerances for ranges of nominal lengths Toler- ance over over over over over class up to 10 30 loo 300 1000 10 up to up to up to up to up to 30 loo 300 1000 3000 H 0.02 0.05 0.1 0.2 0,3 0.4 K 0.05 0,l 0.2 0,4 O, 6 0,8 L 0,l 02 0.4 03 1.2 1.6 5.1.2
26、Circularity The general tolerance on circularity is equal to the numerical value of the diameter tolerance, but in no case shall it be greater than the respective tolerance value for circular radial run-out given in table 4 (see examples in clause 6.2). 5.1.3 Cylindricity General tolerances on cylin
27、dricity are not specified. NOTES 1 The cylindricity deviation comprises three components : circularity deviation, straightness deviation and parallelism deviation of opposite generator lines. Each of these components is controlled by its in- dMdually indicated or its general tolerance. 2 If, for fun
28、ctional reasons, the cylindricity deviation has to be smaller than the combined effect (see clause B.3) of the general tolerances on circularity, straightness and parallelism, an individual cylindricity toler- ance in accordance with IS0 1101 should be indicated for the feature concerned. Sometimes,
29、 e.g. in the case of a fit, the indication of the envelope requirement E is appropriate. O 5.2 Tolerances for related features 5.2.1 General The tolerances specified in 5.2.2 to 5.2.6 apply to all features which are in relation to one another and which have no respec- tive individual indication. 5.2
30、.2 Parallelism The general tolerance on parallelism is equal to the numerical value of the size tolerance or the flatnesdstraightness toler- ance, whichever is the greater. The longer of the two features shall be taken as the datum; if the features are of equal nominal length, either may be taken as
31、 the datum (see clause 8.4). 5.2.3 Perpendicularity The general tolerances on perpendicularity are given in table 2. The longer of the two sides forming the right angle shall be taken as the datum; if the sides are of equal nominal length, either may be taken as the datum. Table 2 - General toleranc
32、es on perpendicularity Values in millimetres Perpendicularity tolerances for ranges of nominal lengths of the shorter sida Toler- class 5.2.4 Symmetry The general tolerances on symmetry are given in table 3. The longer of the two features shall be taken as the datum; if the features are of equal nom
33、inal length, either may be taken as the datum. NOTE - The general tolerances on symmetry apply where - - at least one of the two features has a median plane, or the axes of the two features are perpendicular to each other. See examples in clause B.5. Table 3 - General tolerances on symmetry Values i
34、n millimetres Toler- nominal lengths IKI I 03 I 1 I 5.2.5 Coaxiality General tolerances on coaxiality are not specified. NOTE - The deviation in coaxiality may, in an extreme case, be as great as the tolerance value for circular radial run-out given in table 4, since the deviation in radial run-out
35、comprises the deviation in coaxial- ity and the deviation in circularity. 5.2.6 Circular run-out The general tolerances on circular run-out (radial, axial and any surface of revolution) are given in table 4. CEN EN*227b8-2 93 m 3404589 004b9b8 019 m Tolerance class H K Page 6 EN 22768-2 : 1993 Circu
36、lar run-out tolerances o. 1 0.2 For general tolerances on circular run-out, the bearing surfaces shall be taken as the datum if they are designated as such. Otherwise, for circular radial run-out, the longer of the two features shall be taken as the datum ; if the features are of equal nominal lengt
37、h, either may be taken as the datum. I L I 03 I 6 Indications on drawings 6.1 If general tolerances in accordance with this part of IS0 2768 shall apply in conjunction with the general tolerances in accordance with IS0 2768-1, the following information shall be indicated in or near the title block:
38、. ai “IS0 2768“; b) the tolerance class in accordance with IS0 2768-1; c) the tolerance class in accordance with this part of IS0 2768. EXAMPLE IS0 2766-mk In this case the general tolerances for angular dimensions in ac- cordance with IS0 2768-1 do not apply to right angles (90), which are implied
39、but not indicated, because this part of IS0 2768 specifies general tolerances on perpendicularity. 6.2 If the general dimensional tolerances (tolerance class m) shall not apply, the respective letter shall be omitted from the designation to be indicated on the drawing : EXAMPLE IS0 27-K 6.3 In cases
40、 where the envelope requirement also applies to all single features of sue), the designation “E“ shall be added to the general designation specified in 6.1 : EXAMPLE IS0 278-mK-E NOTE - The envelope requirement cannot apply to features with individually indicated straightness tolerances which are gr
41、eater than their size tolerances, e.g. stock material. 7 Rejection Unless otherwise stated, workpieces exceeding the general geometrical tolerance shall not lead to automatic rejection pro- vided that the ability of the wkpiece to function is not im paired (see clause A.4). 1) For the purposes of th
42、is part of IS0 2768, a single feature of size comprises a cylindrical surface or two parallel plane surfaces. CEN EN+22768-2 93 3404589 0046969 T55 Page 7 EN 2276-2 : 1993 Annex A (informative) Concepts behind general tolerancing of geometrical characteristics A.l General tolerances should be indica
43、ted on the drawing by reference to this part of IS02768 in accordance with clause 6. The values of general tolerances correspond to grades of customary workshop accuracy, the appropriate tolerance class being selected and indicated on the drawing. A.2 Above a certain tolerance value, which correspon
44、ds to the customary workshop accuracy, there is usually no gain in manufacturing economy by enlarging the tolerance. In any event, workshop machinery and the usual workmanship nor- mally do not manufacture features with greater deviations. For example, a feature of 25 mm f 0,l mm diameter by 80 mm l
45、ong manufactured in a workshop with a customary accuracy equal to or finer than IS0 2768-mH contains the geometrical deviations well within 0,l mm for circularity, 0,l mm for straightness of surface elements, and 0,l mm for circular radial run-out (the values given have been taken from this part of
46、IS0 2768). Specifying tolerances would be of no benefit in this particular workshop. However, if, for functional reasons, a feature requires a smaller tolerance value than the “general tolerances“, then that feature should have the smaller tolerance indicated individually adja- cent to the particula
47、r feature. This type of tolerance falls out- side the scope of general tolerances. In cases where the function of a feature allows a geometrical tolerance equal to or larger than the general tolerance values, this should not be individually indicated, but should be stated on the drawing as described
48、 in clause 6. This type of tolerance allows full use of the concept of general geometrical roierancing . There will be “exceptions to the rule“ where the function allows a larger tolerance than the general tolerances, and the larger tolerance will provide a gain in manufacturing economy. In these sp
49、ecial cases, the larger geometrical tolerance should be indicated individually adjacent to the particular feature, e.g. the circularity tolerance of a large and thin ring. A.3 Using general geometrical tolerances leads to the following advantages : a) drawings are easier to read and thus communication is made more effective to the user of the drawing ; b) the design draughtsman saves time by avoiding detailed tolerance calculations as it is sufficient only to know that the function allows a tolerance greater than or equal to the general tolerance ; c) the drawi
