1、BSI BS*947: PART*2 72 = Lb24667 0325083 20T = BRITISH STANDARD Screwing taps Part 2. Specification for Unified ground thread taps: manufacturing tolerances UDC 621.993-181 : 621.882.082 BS 949 : Part 2 : 1992 Committees responsible for this British Standard Board and comes into effect on Amd. No. 15
2、 December 1992 The preparation of this British Standard was entrusted by the Machine, Engineers and Hand Tools Standards Policy Committee (MTE/-) to Technical Committee MTE/4, upon which the following bodies were represented: Date Text affected British Electrical Systems Association (BEAMA Ltd.) Fed
3、eration of British Engineers Tool Manufacturers 0 BSI 1992 First edition April 1979 Second edition December 1992 The following BSI references relate tothe work on this standard: Committee reference MTE4 Draft for comment 90/79112 DC ISBN O 680 21016 2 BSI BS*q: PART*2 92 m Lh4hh 0325083 O82 m BS 949
4、 : Part 2 : 1992 Contents Committees responsible Foreword page Inside front cover 3 Specification 1 Scope 4 2 References 4 3 Right-hand and left-hand threads 4 4 Tolerance classes of taps 4 6 Marking 11 6 Dimensions and manufacuturing tolerances of the threaded portion 6 Annexes A B C (informative)
5、Bases of calculation of the tolerances on the threaded (informative) Example of calculation of the dimensions of the threaded portion of a tap (normative) %ips for BSW, BSF and BA threads (obsolescent) portion of taps for Unified threads 12 17 18 ibles 1 Formulae for limits of tolerance for ground t
6、hread taps for Unified threads 2 Dimensions and manufacturing tolerances for the threaded portion of UNC taps 3 Dimensions and manufacturing tolerances for the threaded portion of UNF taps 4 Tolerances on cumulative pitch for ground thread taps for Unified threads A.l Values of elements based on pit
7、ch in basic formulae for taps for Unified threads A.2 Values of elements based on nominal diameter in basic formulae for taps for Unified threads A.3 Values of elements used in calculating the minor diameter from a measured value of the pitch diameter of a tap for Unified threads A.4 %lerances on th
8、read angle of taps for Unified threads B.l Calculation of the dimensions of a ground thread i - 11 UNC tap, class 2 C. 1 Dimensions and manufacturing tolerances for the threaded portion of BSW taps C.2 Dimensions and manufacturing tolerances for the threaded portion of BSF taps C.3 Dimensions and ma
9、nufacturing tolerances for the threaded portion of BA taps, class 2 C.4 Formulae for limits of tolerance for taps for BSW, BSF and BA threads C.6 Values of elements based on pitch in basic formulae for BSW and BSF threads 5 7 9 11 14 15 16 16 17 19 21 23 24 26 - 1 C.6 c.7 C.8 page Values of elements
10、 based on nominal diameter in basic formulae for BSW and BSF threads 26 Values of elements used in calculating the minor diameter from a measured value of the pitch diameter of a tap for a BSW or BSF thread 27 Values of elements used in calculating the minor diameter from a measured value of the pit
11、ch diameter of a tap for a BA thread 27 BSI BSX949: PARTX2 92 W 1624667 0325084 TL9 W BS 949 : Part 2 : 1992 Figures 1 Relationship of tap classes to nut tolerances 6 A.l Minimum values of tap major diameter d 12 A.2 ?ap minor diameter dl 13 List of references Inside back cover BSI BS*949: PARTIK2 9
12、2 m 31624669 0325085 955 m BS 949 : Part 2 : 1992 Foreword This Part of BS 949 has been prepared under the direction of the Machine, Engineers and Hand Tbols Standards Policy Committee, and supersedes BS 949 : Part 2 : 1979 which is withdrawn. In 1989 the European Committee for Standardization (CEN)
13、 endorsed IS0 2857 : 1973 and IS0 5967 : 1981, published by the International Organization for Standardization (ISO), as EN 22857 : 1989 and EN 25967 : 1989 respectively. Both were given the status of national standards without modification, with the publication of BS 949 : Part 4 : 1990 (identical
14、with EN 22857) and Part 5 : 1990 (identical with EN 25967) which fulfils the United Kingdom obligations as a member of CEN in this respect. BS 949 : Part 2 : 1979 has been revised to withdraw any requirements conflicting with EN 22857 and EN 25967. The thread manufacturing tolerances shown in this P
15、art of BS 949 remain unchanged from those shown in the 1979 edition. Unified threads continue to be specified in the body of the standard whilst requirements for obsolescent Whitworth (BSW and BSF) and BA (British Association) threads are given in annex C. When the revisions are complete BS 949 will
16、 consist of the foilowing Parts. Part 1 Part 2 Part3 Part4 Part5 Specification of general dimemions Specificatwn for Unified ground thread taps: manufacturing tolerances Specification for pipe thread tups Specification for metric ground thread taps - manufacturing tohames (identical with EN 22857) N
17、omenclature and terminology (identical with EN 25967) Compliance with a British Standard does not of itself confer immunity from legal obligations. BSI BS+949: PART+2 92 1624bb9 032508b 891 BS 949 : Part 2 : 1992 Specificat ion 1 Scope This Part of BS 949 specifies dimensions and tolerances for scre
18、wing taps for the following threads: a) Unified (IS0 inch) general-purpose screw threads, coarse thread series (UNC), from no. 1 to no. 12 and from in to 4 in diameter in accordance with BS 1580 : Parts 1 b) Unified (IS0 inch) generai-purpos screw threads, fine thread series (UNF), from no. O to no.
19、 12 and from i in to 1; in diameter also in accordance with BS 1580 : Parts 1 c) in annex C, British Standard Whitworth (BSW) threads from i in to 4 in diameter and British Standard Fine (BSF) threads from in to 3 in diameter in accordance with BS 84 : 1956; d) also in annex C, British Association (
20、BA) threads from no. 14 to no. O in accordance with BS 93 : 1951. NOTE 1. Annex A provides information from which may be calculated the dimensions and tolerances of taps for all Unified threads, including the extra fine thread series (UNEF) and the constant-pitch series (UN). NOTE 2. Annex B gives a
21、n example of a calculation of the dimensions of the threaded portion of a tap. 2 References 2.1 Normative references This Part of BS 949 incorporates, by reference, provisions from specific editions of other publications. These normative references are cited at the appropriate points in the text and
22、 the publications are listed on the inside back cover, Subsequent amendments to, or revisions of, any of these publications apply to this Part of BS 949 only when incorporated in it by updating or revision. 2.2 Informative reference This Part of BS 949 refers to another publication that provides inf
23、ormation. The edition of this publication current at the time of issue of this standard is given on the inside back cover, but reference should be made to the latest edition. 3 Right-hand and left-hand threads Unless left-hand threads are specified in the order (see 6.2.3), any reference to taps con
24、forming to this Part of BS 949 shall be assumed to be to taps for right-hand threads. 4 lblerance classes of taps 4.1 Selection of tap tolerance class Bps intended mainly for the production of Unified nuts of class 3B shall be designated class 1. laps intended mainly for the production of Unified nu
25、ts of class 2B shall be designated class 2. Bps intended mainly for the production of Unified nuts of class 1B shall be designated class 3. NOTE. The relationship between the class of tap and the class of nut to be produced is only of a general nature, as the accuracy of tapping varies with a number
26、 of factors such as the material being tapped, the condition of the machine tool, the tapping attachment, the tapping speed and the lubricant used. Users are therefore recommended to select in each case, from previous experience or from special purpose tests, the most suitable class of tap for the m
27、anufacture of any required class of component thread. 4.2 Differences between the classes NOTE 1. Xps of the different classes vary in the limits of size of the tap major diameter and pitch diameter. The tap major diameter and pitch diameter shall conform to the formulae given in table 1. NOTE 2. Th
28、e relationship between the different classes of tap and their relationship with the nut pitch diameter are illustrated in figure 1. 4 ES1 BSX949: PARTS2 92 W 1624669 0325087 728 BS 949 : part 2 : 1992 B 8 3 rl U 8 Cu + e m Cu - for class 2 and class 3 taps, 0.011 mm. 5.4.2 Merances on thread lengths
29、 other than 25 mm shall be as specified in table 4. )Each flank angle of the Unified thread form is 30, i.e. the included angle is 60 (see BS 1580 : Parts 1 - 7 li - 6 1; - 6 1; - 5 2 - 4.5 2; - 4.5 2: - 4 2: - 4 3-4 3; - 4 3; - 4 33 - 4 4-4 L1 2 12 Approximat1 pitch P O. 3969 0.4536 0.5292 0.6350 O
30、. 6350 O. 7938 O. 7938 1.0583 1.0583 1.2700 1.4111 1.5875 1.8143 1.9538 2.1167 2.3091 2.5400 2.8222 3.1750 3.6286 3.6286 4.2333 4.2333 5.0800 5.6444 5.6444 6.3500 6.3500 6.3500 6.3500 6.3500 6.3500 6.3500 I hic Rajar beter 1.854 2.184 2.515 2.845 3.175 3.505 4.166 4.826 5.486 6.350 7.938 9.525 11.11
31、2 12.700 14.288 15.875 19.050 22.225 25.400 28.575 31.750 34.925 38.100 44.450 50.800 57.150 63.500 69.850 76.200 82.550 88.900 95.250 101.600 i Basic pitch liameter 1.598 1.890 2.172 2.433 2.763 2.990 3.650 4.138 4.798 5.524 7.021 8.494 9.934 11.430 12.913 14.376 17.399 20.391 23.338 26.218 29.393
32、32.174 35.349 41.151 47.135 53.485 59.375 65.725 72.075 78.425 84.775 91.125 97.475 :lass 1 mor diameter m. Leviation s t 0.031 t 0.033 +0.036 t 0.042 t 0.042 t O. 047 t 0.047 t 0.053 + 0.052 + O. 058 + 0.060 + 0.066 + 0.071 + 0.074 + 0.077 + 0.079 +0.081 + 0.087 + O. 092 +0.101 +o. 100 +o. 109 +o.
33、108 +0.117 +O. 125 +O. 124 +O. 133 +O. 132 +O. 132 +O. 131 +O. 131 +O. 130 +O. 130 m. 1.885 2.217 2.551 2.887 3.217 3.552 4.213 5.879 5.538 6.408 7.998 9.591 11.183 12.774 14.365 15.956 19.131 22.312 25.492 28.676 31.850 35.034 38.208 44.567 50.925 57.274 63.633 69.982 76.332 82.681 89.031 95.380 10
34、1.730 itch diameter 1; 1; 1; 1: 2 2; 2: 2“ 3 3: 3; 3“ 4 9 16 1 BSI BSS949: PARTS2 92 W 1b24bb9 0325091 159 W Bs949:Part2:1992 IBble 3. Dimensions and manufacturing tolerances for the threaded portion of UNF taps i 1 11 WS 2 1 Designation NO. O - 80 NO. 1 - 72 NO. 2 - 64 NO. 3 - 56 NO. 4 - 48 NO. 5 -
35、 44 NO. 6 - 40 NO. 8 - 36 NO. 10 - 32 NO. 12 - 28 f - 28 - 24 - 24 - 12 1; - 12 2 Approximatt pitch P 0.3175 0.3528 0.3969 0.4536 0.5292 0.5773 0.6350 O. 7056 O. 7938 0.9071 0.9071 1.0583 1 .O583 1.2700 1.2700 1.4111 1.4111 1.5875 1.8143 2.1167 2.1167 2.1167 2.1167 2.1167 # hic najor iiameter 1.524
36、1.854 2.184 2.515 2.845 3.175 3.505 4.166 4.826 5.486 6.350 7.938 9.525 11.112 12.700 14.288 15.875 19.050 22.225 25.400 28.575 31.750 34.925 38.100 4 Basic pitch diameter 1.318 1.626 1.928 2.220 2.502 2.799 3.094 3.708 4.310 4.897 5.761 7.249 8.837 10.287 11.874 13.371 14.958 18.019 21.046 24.026 2
37、7.201 30.376 33.551 36.726 i 16 17 18 19 I lo hs I Major diameter m. leviation 4 + 0.028 + 0.031 +0.031 + 0.033 + 0.036 + 0.039 + 0.041 + 0.044 + 0.047 + 0.049 + 0.049 +0.051 +0.051 + O. 056 +0.056 + 0.059 +0.058 +0.063 +0.069 +0.074 +0.074 + 0.073 +0.073 +0.072 Min. 1.552 1.885 2.215 2.548 2.881 3.
38、214 3.546 4.210 4.873 5.535 6.399 7.989 9.576 11.168 12.756 14.347 15.933 19.113 22.294 25.474 28.649 31.823 34.998 38.172 teh diameter Bwer leviation cm t 0.006 t0.007 t0.006 t0.007 +0.008 +0.009 + 0.009 +0.010 +0.011 +0.011 +0.011 +0.011 + 0.011 + 0.012 + 0.012 + 0.013 + 0.012 + 0.013 +0.015 + 0.0
39、16 +0.016 +0.015 +0.015 +0.014 fi. 1.324 1.633 1.934 2.227 2.540 2.808 3.103 3.718 4.321 4.908 5.772 7.260 8.848 10.299 11.886 13.384 14.970 18.032 21.061 24.042 27.217 30.391 33.566 36.740 Upper deviation 4 +0.016 + 0.017 + 0.017 + 0.019 + 0.020 + 0.021 +0.023 +0.024 +0.025 +0.027 +0.027 + 0.029 +
40、0.029 +0.032 + 0.032 + 0.033 + 0.034 + 0.035 + 0.039 +0.042 + 0.042 +0.043 +0.043 +0.044 Max. 1.334 1.643 1.945 2.239 2.522 2.820 3.117 3.732 4.335 4.924 5.788 7.278 8.866 10.319 11.906 13.404 14.992 18.056 21.085 24.068 27.243 30.419 33.594 36.770 kqjor iameter m. leviation rS t 0.033 t O. 036 +0.0
41、36 + 0.039 + 0.042 +0.045 +0.048 + 0.051 + 0.054 + 0.057 +0.057 +0.060 +0.060 +0.066 +0.066 + 0.069 + 0.069 + O. 075 +0.081 + 0.087 + 0.087 + 0.087 +0.087 + 0.087 m. 1.557 1.890 2.220 2.554 2.887 3.220 3.553 4.217 4.880 5.543 6.407 7.998 9.585 11.178 12.766 14.357 15.944 19.125 22.306 25.487 28.662
42、31.837 35.012 38.187 bee 5.3. NOTE. For an explanation of the terms .is, E, and E, see BS 949 : Part 5. 9 BSI BSJ949: PART*2 92 m Lb24bb9 0325092 095 m 12 13 14 15 16 meter 17 Min. 1.557 1.890 2.220 2.554 2.887 3.220 3.553 4.217 4.880 5.543 6.407 7.998 9.585 11.178 12.766 14.357 15.944 19.125 22.306
43、 25.487 28.662 31.837 35.012 38.187 1s 19 20 21 22 Pitch diameter Lower deviation Em +0.011 +0.012 +0.012 + 0.013 + 0.014 +0.015 + 0.016 + 0.017 + 0.018 + 0.019 + 0.019 + 0.020 + 0.020 + 0.022 + 0.022 + 0.023 + 0.023 +0.025 +0.027 +0.029 +0.029 +0.029 + 0.029 +0.029 Min. 1.329 1.638 1.940 2.233 2.51
44、6 2.814 3.110 3.725 4.328 4.916 5.780 7.269 8.857 10.309 11.896 13.394 14.981 18.044 21.073 24.055 27.230 30.405 33.580 36.755 upper ieviation 5 + O. 026 + 0.028 + 0.029 + 0.031 + 0.032 + 0.034 + 0.036 +0.038 + 0.040 + 0.042 + 0.043 +0.046 +0.048 +0.051 + 0.052 + 0.054 + 0.056 + 0.060 + 0.064 +0.067
45、 +0.069 + O. 070 + 0.071 + 0.073 Max. 1.344 1.654 1.957 2.251 2.534 2.833 3.130 3.746 4.350 4.939 5.804 7.295 8.885 10.338 11.926 13.425 15.014 18.079 21.110 24.093 27.270 30.446 33.622 36.799 Linear dimensions in mametre5 Mqjor diameter Min. deviation 3s + 0.048 + 0.052 +0.053 + 0.057 + 0.060 + 0.0
46、64 +0.068 + 0.072 + 0.076 + 0.080 +0.081 +0.086 + 0.088 + 0.095 t0.096 +o. 101 +o. 102 +0.110 +0.118 + O. 125 +O. 127 +O. 128 +O. 129 +O. 131 Kin. 1.572 1.906 2.237 2.572 2.905 3.239 3.573 4.238 4.902 5.566 6.431 8.024 9.613 11.208 12.796 14.389 15.977 19.160 22.343 25.525 28.702 31.878 35.054 38.23
47、1 Pitch diameter Lower deviation Ern + 0.026 + 0.028 + 0.029 +0.031 + 0.032 +0.034 + 0.036 + 0.038 +0.040 +0.042 +0.043 +0.046 +0.048 +0.051 + 0.052 + 0.055 + 0.056 +0.060 + 0.064 +0.067 +0.069 +0.070 + 0.071 + 0.073 Min. 1.344 1.653 1.955 2.251 2.533 2.834 3.129 3.746 4.350 4.939 5.804 7.297 8.886
48、10.339 11.927 13.426 15.014 18.079 21.111 24.092 27.269 30.445 33.621 36.798 upper leviation 4 + 0.041 + 0.044 + 0.046 +0.049 + 0.050 + 0.053 + 0.056 + 0.059 +0.062 +0.065 0.067 +0.072 +0.076 + 0.080 +0.082 + 0.087 + 0.089 +0.095 t o. 101 +O. 105 +o. 109 +0.111 +0.113 +0.117 Kax. 1.359 1.669 1.972 2
49、.269 2.551 2.853 3.149 3.767 4.372 4.962 5.828 7.325 8.914 10.368 11.957 13.458 15.047 18.114 21.148 24.130 27.309 30.486 33.663 36.842 23 Tolerance on thread anael) degrees 2.2 2.1 2.0 1.9 1.7 1.7 1.6 1.5 1.4 1.3 1.3 1.2 1.2 1.1 1.1 1.1 1.1 1.0 0.9 0.9 0.9 0.9 0.9 0.9 14 VOminal size No. o No. 1 No. 2 No. 3 No. 4 No. 5 No. 6 No. 8 No. 10 No. 12 i 3 is 3 B 7 iij 1 9 m B i 1 li if 1% 1; 3 BSI BS+949: PARTr2 92 = lb24669 0325093 T2L BS949:Part2: 1992 rable 4. Tolerances on cumulative pitch for ground thread taps for Unified threads 1 12 Length of thrd Qbove
