Disclosure to Promote the Right To Information

Transcription

1 इ टरन ट म नक Disclosure to Promote the Right To Information Whereas the Parliament of India has set out to provide a practical regime of right to information for citizens to secure access to information under the control of public authorities, in order to promote transparency and accountability in the working of every public authority, and whereas the attached publication of the Bureau of Indian Standards is of particular interest to the public, particularly disadvantaged communities and those engaged in the pursuit of education and knowledge, the attached public safety standard is made available to promote the timely dissemination of this information in an accurate manner to the public. ज न1 क अ+धक र, ज 1 क अ+धक र Mazdoor Kisan Shakti Sangathan The Right to Information, The Right to Live पर 1 क छ ड न' 5 तरफ Jawaharlal Nehru Step Out From the Old to the New IS 78-4 (1999): ISO Metric Trapezoidal Screw Threads, Part 4: Tolerances [PGD 2: Engineering Standards]! न $ एक न' भ रत क +नम-ण Satyanarayan Gangaram Pitroda Invent a New India Using Knowledge! न एक ऐस खज न > ज कभ चर य नहB ज सकत ह ह Bhartṛhari Nītiśatakam Knowledge is such a treasure which cannot be stolen

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4 IS78(Part4):1999 ISO293:1993 Indian Standard IS METRIC TRAPEZOIDAL SCREW THREADS PART 4 TOLERANCES ( Second Revision ) ICS b BIS 1999 BUREAU Of INDIAN STANDARDS MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG NEW DELttl May 1999 ~GrOUpS

5 Engineering Standards Sectional Committee, LM 1 NATIONAL FOREWORD This Indian Standard (Part 4) (Second Revision) which is identical with IS 2993 : 1993 IS metric trapezoidal screw threads - Tolerances, issued by the International Organization for Standardization (ISO) was adopted by the Bureau of Indian Standards on the recommendation of the Engineering Standards Sectional Committee and approval of the Light Mechanical Engineering Division Council. This standard was originally issued in 1973 and subsequently revised in The first revision was harmonized with IS Standard by adopting IS 293 : This second revision has been taken up to align it with the latest version of IS 293, which has been technically revised in The text of IS Standard has been approved as suitable for publication as Indian Standard without deviations. In the adopted standard certain conventions are not identical to those used in Indian Standards; attention is especially drawn to the following: a) Wherever the words International Standard appear referring to this standard, they should be read as Indian Standard. b) Comma (,) has been used as a decimal marker while in Indian Standards, the current practice is to use a full point (.) as the decimal marker. In this adopted standard, reference appears to certain International Standards for which Indian Standards also exist. The corresponding Indian Standards which are to be substituted in their place are listed below along with their degree of equivalence for the editions indicated: lnterna tional Standard IS 965-l ) Corresponding Indian Standard IS - (Part 1): - IS general purpose metric screw threads - Tolerances: Part 1 Principle and basic data (under preparation) Degree of Equivalence Identical ~ IS 291 : 1993 IS 78 (Part 1) : 1999 IS metric trapezoidal screw threads: Part 1 Basic profile and maximum material profile (second revision) IS 2962 : 1977 IS 78 (Part 2) : 1988 IS metric trapezoidal screw threads: Part 2 Pitch diameter combination (first revision) do do IS 548 : 1983 IS 1587 : 1983 Terminology for screw Technically threads Equivalent This standard (Part 4) covers the tolerances for IS metric trapezoidal screw threads. The other parts covering various aspects of the IS metric trapezoidal screw threads are given as under: IS No. IS 78 (Part 1) : 1999 Tit/e IS metric trapezoidal screw threads: Part 1 Basic profile and maximum material profile (second revision) ( Con timed on third cover) ) To be published (Revision of IS 965-l : 198).

6 IS 78 ( Part 4 ) : 1999 Indian Standard IS METRIC TRAPEZOIDAL SCREW THREADS PART 4 TOLERANCES ( Second Revision ) 1 Scope This international Standard specifies a tolerance system for metric trapezoidal screw threads in accordance with IS 292. The tolerances refer to the basic profile IS 291. The tolerance system does not apply to trapezoidal screw threads with special requirements on axial displacement, for example lead screws. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and IS maintain registers of currently valid International Standards. 4 Symbols (See figures 1 to 4) 4 DI 4 d 4 dz P ph N L N T T Dl =~2 r, Tff3 basic major diameter of nut thread, in millimetres basic minor diameter basic pitch diameter of nut thread, in millimetres of nut thread, in millimetres basic major diameter of bolt thread, in millimetres basic minor diameter of bolt thread, in millimetres basic pitch diameter pitch, in millimetres lead, in millimetres of bolt thread, in millimetres designation for thread engagement group Normal designation for thread engagement group Long thread engagement, tolerance, in micrometres in millimetres tolerances for D,, 4, d, 4, Cr, (for D, no tolerances are specified), in micrometres IS 965-l :I 98, IS general purpose metric screw threads - Tolerances - Part 1: Principles and basic data. IS 291 :1993, IS metric trapezoidal screw threads - Basic profile and maximum material profiles. IS 292: 1977, IS metric trapezoidal screw threads - General plan. Td2 ei, EI es, ES lower deviations (EI for nut threads is equal to zero), in micrometres upper deviations, in micrometres IS 548:1983, Cylindrical screw threads - Vocabulary. 3 Definitions For the purposes of this International Standard, the definitions given in IS 548 apply. 5 Structure of the tolerance system The system is based on the tolerance system for IS general-purpose metric screw threads of IS 965-1, completed with tolerance positions c and e, and with values for pitches above 6 mm. The recommended tolerance classes are, however, not the same as those for IS metric screw threads in IS 965-l. 1

7 IS 78 ( Part 4 ) : Tolerance grades 7 Tolerance positions The following tolerance grades are established:. :_h [Pitchline Tolerance grades Minor diameter of nut threads D, : 4 Major diameter of bolt threads d : 4 Pitch diameter of nut threads D2 : 7 a 9 Pitch diameter of bolt threads 4 : (6) 7 a 9 Minor diameter of bolt threads d3 : 7 a 9 es ei Figure 1 - Tolerance positions with respect to zero line (basic size) Tolerance grade 6 for the pitch diameter (4) of the bolt thread has been included only as a means to establish the pitch diameter tolerances of grades 7, 8 and 9. See The tolerance grade for the minor diameter (4) of the bolt thread is always the same as for the pitch diameter (di). However, the values for Td3 and Td2 are not the same for a same grade because Td3 = 1,25T,, + lesl. The following tolerance positions are standardized for the pitch diameter. a) For nut threads: H with zero fundamental deviation (see figure 2 and table 1). b) For both threads: c and e with negative fundamental deviation (see figure 3 and table I). The tolerance position for the minor diameter D, and the major diameter DA of the nut threads is always H, i.e. with zero fundamental deviation. The tolerance position for the major diameter d and minor diameter da of the bolt threads is in all cases h, i.e. with zero fundamental deviation, and it is independent of the tolerance position of the pitch diameter. P Figure 2 - Nut threads with tolerance position H for the pitch diameter 2

8 IS 78( Part 4): 1999 Figure 3 - Bolt threads with tolerance positions c and e for the pitch diameter Table 1 - Fundamental deviations for the oitch diameter of nut threads and bolt thread; Fundamental deviation 8 Lengths of thread engagement The length of thread engagement is classified into the groups N or L, in accordance with table2. Pitch P Nut thread D, f Bokthread 9 Crest and root diameter tolerances mm H El m i C es e es Minor diameter tolerances of nut thread (TD,) For the minor diameter tolerance of the nut thread, To,, there is only one tolerance grade, 4 (see table3). 7 a Major diameter tolerances of bolt thread WJ For the major diameter tolerance of the bolt thread, T,, there is only one tolerance grade, 4 (see table4) Minor diameter tolerances of bolt thread IT,) : For the minor diameter tolerance of the bolt thread, -4-2 T&, there are three tolerance grades, 7, 8, and 9, in accordance with table : Pitch diameter tolerances For the pitch diameter tolerances there are three tolerance grades, 7, 8 and 9 for nut threads, in accordance with table6, and four tolerance grades, 6, 7, 8 and 9 for bolt threads, in accordance with table7. 3

9 IS 78( Part 4):1999 Table 2 - Basic major diameter d over up to and incl Lengths of thread engagement Dimensions in mllihmetres Groups of lengths of thread engagement, I Pitch N L P over up to and incl. over I 19 G&-l--k I 75 I 236 I I 9 I 265 I I 112 I I 132 I I I

10 IS 78( Part 4): 1999 Table 3 - Minor diameter tolerances of nut thre k U-i,,) Pitch P Tolerance Grade 4 mm Table 4 - Major diameter tolerances of bolt threads (T,) Pitch P Tolerance grade 4 mm w , Basic major diameter d Table 5 - Minor diameter tolerances of bolt thread (T,) Pitch Tolerance position Tolerance position C e p I of the pitch diameter tolerance of the pitch diameter tolerance I over up to I Tolerance grades I Tolerance grades I I * I g I I * I g mm mm mm pm lm km pm pm pm , I I I 1 I I I I I I I I I 5

11 IS 78 ( Part 4 ) : 1999 Basic major diameter Pitch Tolerance position Tolerance position C e d P of the pitch diameter tolerance of the pitch diameter tolerance over up to Tolerance grades Tolerance grades mm mm mm pm pm pm pm 1i-n pm ii

12 IS 78 ( Part 4 ) : 1999 IS 293 :1993 Table 6 - Pitch diameter tolerances of nut thread (Z & Basic major diameter Pitch Tolerance grades d P over up to and incl mm mm mm pm pm pm I, ,2 : z z , : :

13 IS 78 ( Part 4 ) : 1999 Table._I._ 7 - m Pitch diamntnr..-.e.. _....a._. tnlnranmr._.,i.. nf hnl+ thrrmrl IT ~\ _. Y....mm,I \A&, Basic major diameter Pitch Tolerance grades d P over up to and incl. 6 7 a 9 mm mm mm w-n Pm vm pm : : :

14 IS 78(Patt4):1999 Figure 4 - Lead and pitch of multiple-start thread 11 Recommended tolerance classes 12 Multiple-start threads In order to reduce the number of gauges and tools, the tolerances should preferably be chosen from tables 8 and 9. The following general rules can be formulated for the choice of tolerance quality. a) Medium: for general use. b) Coarse: for cases when manufacturing difficulties can arise. If the actual length of thread engagement group N is recommended. is unknown, The tolerances for multiple-start threads (see figure 4) are the same as for single-start threads, with the exception of the pitch diameter tolerances which are enlarged. The tolerance values for TD2 and Td2, specified in tables 6 and 7, shall, for multiple-start threads, be multiplied by a factor according to table 1. Table 1 - Factors for multiple-start threads Number of starts and larger Factor Table 8 - Recommended tolerance classas for nut threads Tolerance quality I Tolerances for the pitch 1 diameter _ Medium 7H 8H Coarse 8H 9H N/ 13 Formulae 13.1 Fundamental deviations The fundamental deviations for nut and bolt threads have been calculated according to the following formulae. for EI, = es, = - ( IP) for P up to and including 2 es,=-5+94,12fiforp=3top=44 Table 9 - Recommended tolerance classes for bolt threads I Tolerances for the pitch I Tolerance quality I+?+ Medium 7e 8e Coarse 8c 9c es, = - (5 + 1 lf) for Pup to and including 3 es, = - 47,49$ for P = 4 to P = Length of thread engagement For the calculation of the limits of the normal length of thread engagements IN in table 2, the following rule has been applied. For each pitch within a certain diameter range, d has been set equal to the smallest diameter (within the range) which appears in table 2.

15 IS 78 ( Part 4 ) : 1999 IN min. I 2,24Pd ** IN max. = 6,7Pd 13.3 Crest diameter tolerances Tolerances for minor diameter of nut thread (T,,) The T,, tolerances for grade 4 are calculated according to the following formula: T,, =,63 (23OP ) Tolerances for major diameter of bolt thread (Td) The Td tolerances for grade 4 are calculated according to the following formula: T,=O, x Tolerances for minor diameter of bolt thread (T,) The T& tolerances are obtained from the Ta values according to the following formula: Td3 = 1,25T, + le.sl 13.4 Pitch diameter tolerances Tolerances for pitch diameter of nut thread (TD2) The TD2 tolerances are obtained from the tolerances for grade 6, Td2 (61, (see table71 according to table 11. I Table 11 - fi I Tolerances for pitch diameter of nut thread (To21 Tolerance grades ,7T, ( Ta (6) 2.65~~ (6) Tolerances for pitch diameter of bolt thread (Td2) The Td2 tolerances are calculated according to the following formulae (d equal to the geometrical mean value of the diameter range limits): Ta (6) = 9Por4 x do* T, (7) = 1,257 (6) Ta (6) = 1,6T,, (6) Tn (9) = 2% (6) 13.5 Ruies of rounding The values for pitch and crest diameter tolerances and for fundamental deviations have been calculated for the formulae above and then rounded off to the nearest value in the R4 series of preferred numbers. The calculated values for the minor diameter tolerances Td3 have not been rounded. 14 Designation A complete designation for a screw thread shall comprise a designation for the thread system and size, and a designation for the thread tolerance. The thread designation shall be as given in IS 292. The tolerance designation consists of a symbol for the pitch diameter tolerance only. There is no need to designate the crest diameter tolerance since - the tolerance position is always the same; - only one tolerance grade is established for the minor diameter of nut threads,) and for the major diameter of bolt threads (di. Each tolerance designation shall comprise: - a figure indicating the grade ot the pitch diameter tolerance; - a letter indicating the position of the pitch diameter tolerance, capital for nuts, small for halts. EXAMPLES For nut threads: Tr 4 x 7-7H For bolt threads: Tr 4 x 7-78 For two-start, left-hand bolt threads: Tr 4 x 14 (P7) LH - 7e A fit between threaded parts is indicated by the nut thread tolerance designation followed by the bolt thread tolerance designation separated by a stroke. EXAMPLES Tr 4 x 7-7H/7e Tr 4 x 14 (P7) - 7H/7e 1

16 (Continued from second cover) IS No. IS 78 (Part 2) : 1988 IS 78 (Part 3) : 1988 IS 7684 : 1975 IS 7685 : 1975 IS 7726 : 1975 IS 7727 : 1975 Tit/e IS metric trapezoidal screw threads: Part 2 Pitch diameter combination ( first revision) IS metric trapezoidal screw threads: Part 3 Basic dimensions (first revision) Limits of sizes for IS metric trapezoidal nut threads (diameter range 8 to 1 mm) Limits of sizes for IS metric trapezoidal bolts threads (diameter range 8tolOOmm) Limits of sizes for IS metric trapezoidal nut threads (diameter range 15 to 3 mm) Limits of sizes for IS metric trapezoidal bolts threads (diameter range 15 to 3 mm) For the purpose of deciding whether a particular requirement of this standard is complied with, the final value, observed or calculated, expressing the result of a test or analysis, shall be rounded off in accordance with IS 2 : 196 Rules for rounding off numerical values (revised). The number of significant places retained in the rounded off value should be the same as that of the specified value in this standard.

17 Bureau of Indian Standards BIS is a statutory institution established under the Bureau of Indian Standards Act, 1986 to promote harmonious development of the activities of standardization, marking and quality certification of goods and attending to connected matters in the country. Copyright BIS has the copyright of all its publications. No part of these publications may be reproduced in any form without the prior permission in writing of BIS. This does not preclude the free use, in the course of implementing the standard, of necessary details, such as symbols and sizes, type or grade designations. Enquiries relating to copyright be addressed to the Director (Publication), BIS. Review of Indian Standards Amendments are ssued to standards as the need arises on the basis of comments. Standards are also reviewed periodically; a standard along with amendments is reaffirmed when such review indicates that no changes are needed; if the review indicates that changes are needed, it is taken up for revision. Users of Indian Standards should ascertain that they are in possession of the latest amendments or edition by refirring to the latest issue of BIS Handbook and Standards Monthly Additions This Indian Standard has been developed from Dot: No. LM Ol(O37). Amendments Issued Since Publication Amend No. Date of Issue Text Affected Headquarters: BUREAU OF INDIAN STANDARDS Manak Bhavan, 9 Bahadur Shah Afar Marg, New Delhi 112 Telephones: , , Regional Offices: Central Eastern : Manak Bhavan, 9 Bahadur Shah Zafar Marg NEW DELHI 112 : l/14 C.I.T. Scheme VII M, V.I.P. Road, Maniktola CALCUTTA 754 Northern : SCG , Sector 34-A, CHANDIGARH 1622 Southern : C.I.T. Campus, IV Cross Road, CHENNAI 6113 Weatem : Manakalaya, E9 MIDC, Marol, Andheri (East) MUMBAI493 Brauches : AHMADABAD. BANGALGRE. BHOPAL. BHUBANESHWAR. COIMBATORE. FARIDABAD. GHAZIABAD. GUWAHATI. HYDERABAD. JAIPUR. KANPUR. LUCKNOW. NAGPUR. PATNA. WNE. THIRUVANANTHAPURAM. Telegrams: Manaksanstha (Common to all offices) Telephone , { , ,337 { { ,235 19, ,832 91, _