1、BRITISH STANDARD BS 3409-1: 1961 Incorporating Amendment Nos. 1, 2 and 3 Specification for The tapping of holes to receive wire thread inserts (UNC and UNFthreads) Part 1: Diameters 1 / 4in and overBS3409-1:1961 This British Standard, having been approved by the MechanicalEngineering IndustryStandar
2、ds Committeeand endorsed by theChairman ofthe EngineeringDivisional Council, was published under the authorityof the General Councilon 16August1961 BSI 05-2000 The following BSI references relate to the work on this standard: Committee reference MEE/148 Draft for comment A (MEE) 8221 ISBN 0 580 3525
3、2 8 Co-operating organizations The Mechanical Engineering Industry Standards Committee, under whose supervision this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: The Government departments and scient
4、ific and industrial organization marked with an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the preparation of this standard: Admiralty* High Commission of India Air Ministry Institute of Marine Engineers Associated Offices Techn
5、ical Committee Institute of Petroleum Association of Consulting Engineers Institution of Civil Engineers (Incorporated) Institution of Gas Engineers British Chemical Plant Manufacturers Institution of Heating and Ventilating Association Engineers British Compressed Air Society Institution of Mechani
6、cal Engineers British Electrical and Allied Manufacturers Institution of Mechanical Engineers Association* (Automobile Division) British Engineers Association Institution of Production Engineers British Gear Manufacturers Association Locomotive and Allied Manufacturers British Internal Combustion En
7、gine Association of Great Britain Manufacturers Association Machine Tool Trades Association British Iron and Steel Federation Ministry of Labour (Factory Inspectorate) British Railways, The British Transport Ministry of Power Commission Ministry of Transport Crown Agents for Oversea Governments and
8、Ministry of Works Administrations National Coal Board D.S.I.RNational Engineering Laboratory National Physical Laboratory (D.S.I.R) Electricity Council, The Generating Board and Radio Industry Council the Area Boards in England and Wales War Office* Engineering Equipment Users Association Gas Counci
9、l British Plastics Federation Ministry of Aviation Gauge and Tool Makers Association Screw Thread Tool Manufacturers Association Institute of the Motor Industry (Incorporated) Society of British Aircraft Constructors London Transport Executive, The British Society of Motor Manufacturers and Traders
10、Ltd Transport Commission Individual manufacturers Amendments issued since publication Amd. No. Date of issue Comments 5732 January 1966 5998 January 1967 1180 May 1973 Indicated by a sideline in the marginBS3409-1:1961 BSI 05-2000 i Contents Page Co-operating organizations Inside front cover Forewor
11、d ii 1 Scope 1 Section 1. Tapped holes 2 Form of thread and limits of size 3 3 Identification 3 Section 2. Screwing taps 4 General dimensions 5 5 Marking 5 6 Form of thread 8 7 Limits of size for cutting diameter 8 Section 3. Gauging system 8 General 10 9 Design and general dimensions 10 10 Toleranc
12、es and limits of size 10 Figure 1 Basic form of Unified insert assembly 2 Table 1 Limits and tolerances suitable for tapped holes for inserts for UNC threads, Class2B 3 Table 2 Limits and tolerances suitable for tapped holes for inserts for UNF threads, Class 2B 4 Table 3 Limits and tolerances suita
13、ble for tapped holes for inserts for UNC threads, Class 1B 4 Table 4 Limits and tolerances suitable for tapped holes for inserts for UNF threads, Class 1B 5 Table 5 General dimensions of UNC taps for insert tapped holes 6 Table 6 General dimensions of UNF taps for insert tapped holes 7 Table 7 Toler
14、ances on general dimensions of taps for insert tapped holes 8 Table 8 Limits of size for UNC taps for insert tapped holes 9 Table 9 Limits of size for UNF taps for insert tapped holes 9 Table 10 Tolerances for GO gauges for UNC insert tapped holes 10 Table 11 Tolerances for GO gauges for UNF insert
15、tapped holes 11 Table 12 Tolerances for NOT GO gauges for UNC insert tapped holes 11 Table 13 Tolerances for NOT GO gauges for UNF insert tapped holes 11 Table 14 Tolerances for GO and NOT GO plain plug gauges for minor diameters 12 Table 15 Limits of size for GO gauges for UNC insert tapped holes (
16、all classes) 12 Table 16 Limits of size for NOT GO gauges for insert tapped holes suitable for Class 2B UNC threads 13 Table 17 Limits of size for NOT GO gauges for insert tapped holes suitable for Class 1B UNC threads 13 Table 18 Limits of size for GO gauges for UNF insert tapped holes (All classes
17、) 14 Table 19 Limits of size for NOT GO gauges for insert tapped holes suitable for Class 2B UNF threads 14 Table 20 Limits of size for NOT GO gauges for insert tapped holes suitable for Class 1B UNF threads 15BS3409-1:1961 ii BSI 05-2000 Foreword This standard makes reference to the following Briti
18、sh Standards: BS 919, Screw gauge limits and tolerances Part 1: Gauges for screw threads of Unified form. BS 949, Screwing taps. BS 1044, Recommended designs for plug, ring and gap gauges. BS 1580, Unified screw threads. This British Standard has been prepared under the authority of the Mechanical E
19、ngineering Industry Standards Committee in response to requests received from a manufacturer of wire thread inserts and from the Admiralty. The use of wire thread inserts by many branches of industry has grown rapidly in recent years. Their main purpose is to provide a wear resisting fastening in li
20、ght alloys and similar materials. Their application varies widely: for example, inserts may be called upon to meet design requirements or they may be used for purposes of salvage and repair. It is not considered practicable at the present time to standardize the inserts themselves as their free form
21、 depends on the method of manufacture and several different methods are in use. It may be stated, however, that any of these methods is capable of producing inserts which will provide a standard internal thread if used in a hole tapped to the appropriate limits of size. The object of this standard,
22、therefore, is to give limits of size for tapped holes which, when assembled with an insert, will give the required nominal size and class of tolerance of the internal thread. To assist in achieving this object, limits of size are also recommended for appropriate screwing taps and gauges. It is recog
23、nized that a transition period will necessarily ensue during which existing taps and gauges will continue to be used. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a
24、 British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to15 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This w
25、ill be indicated in the amendment table on the inside front cover.BS 3409-1:1961 BSI 05-2000 1 1 Scope This British Standard comprises three sections: Section 1, which specifies limits of size for tapped holes to accommodate wire thread inserts to provide thread sizes from 1 / 4in to1 1 / 2in UNC in
26、clusive and from 1 / 4in to1in UNF inclusive; Section 2, which recommends screwing taps intended to produce holes to the limits of size specified in Section1; Section 3, which gives a recommended gauging system for checking the tapped holes.BS 3409-1:1961 2 BSI 05-2000 Figure 1 Basic form of Unified
27、 insert assemblyBS 3409-1:1961 BSI 05-2000 3 Section 1. Tapped holes 2 Form of thread and limits of size Holes shall be threaded to provide Class2B or Class1B limits in accordance with BS1580 1)when assembled with the wire thread inserts and shall be of Unified form as illustrated inFigure 1. Holes
28、to provide Class2B limits for 1 / 4in to1 1 / 2in UNC threads inclusive shall be tapped to the limits specified inTable 1. Holes to provide Class2B limits for 1 / 4in to1 in UNF threads inclusive shall be tapped to the limits specified inTable 2. Holes to provide Class1B limits for 1 / 4in to1 1 / 2
29、in UNC threads inclusive shall be tapped to the limits specified inTable 3. Holes to provide Class1B limits for 1 / 4in to1 in UNF threads inclusive shall be tapped to the limits specified inTable 4. NOTEThe limits given inTable 1 toTable 4 are designed to permit the production, under normal conditi
30、ons, of holes to suit the classes of threads stated. Under ideal conditions it may be possible to achieve a closer class of fit on the final installation than those indicated in the tables. 3 Identification In order to distinguish requirements for holes intended to receive inserts from those intende
31、d to receive threaded components it is recommended that the former be clearly identified on drawings and specifications. This may be done by specifying the actual major, effective and minor diameters of the hole and their limits or by the addition of the words “wire insert” and number of this Britis
32、h Standard to the designation of the thread. e.g. 1 / 4 20UNC2B, Wire insert, BS3409. Table 1 Limits and tolerances suitable for tapped holes for inserts for UNC threads,Class2B a 1) BS1580, “Unified screw threads.” 1 2 3 4 5 6 7 8 Designation Major diameter Effective diameter Minor diameter Min. Ma
33、x. Tol. Min. Max. Tol. Min. in in in in in in in 1 / 4 5 / 16 3 / 8 7 / 16 1 / 2 9 / 16 5 / 8 3 / 4 7 / 81 1 1 / 81 1 / 41 3 / 81 1 / 220 UNC 18 UNC 16 UNC 14 UNC 13 UNC 12 UNC 11 UNC 10 UNC 9 UNC 8 UNC 7 UNC 7 UNC 6 UNC 6 UNC 0.3150 0.3847 0.4562 0.5303 0.5999 0.6708 0.7431 0.8799 1.0193 1.1624 1.3
34、106 1.4356 1.5914 1.7164 0.2851 0.3515 0.4189 0.4875 0.5537 0.6208 0.6885 0.8196 0.9522 1.0868 1.2239 1.3490 1.4900 1.6151 0.0026 0.0029 0.0033 0.0036 0.0038 0.0041 0.0044 0.0047 0.0051 0.0056 0.0061 0.0062 0.0068 0.0069 0.2825 0.3486 0.4156 0.4839 0.5499 0.6167 0.6841 0.8149 0.9471 1.0812 1.2178 1.
35、3428 1.4832 1.6082 0.2703 0.3341 0.3985 0.4636 0.5275 0.5918 0.6565 0.7838 0.9124 1.0421 1.1709 1.2959 1.4311 1.5561 0.0095 0.0096 0.0100 0.0106 0.0109 0.0113 0.0118 0.0122 0.0133 0.0150 0.0150 0.0150 0.0200 0.0200 0.2608 0.3245 0.3885 0.4530 0.5166 0.5805 0.6447 0.7716 0.8991 1.0271 1.1559 1.2809 1
36、.4111 1.5361 a See note to Clause2.BS 3409-1:1961 4 BSI 05-2000 Table 2 Limits and tolerances suitable for tapped holes for inserts for UNF threads, Class 2B a Table 3 Limits and tolerances suitable for tapped holes for inserts for UNC threads, Class 1B a 1 2 3 4 5 6 7 8 Designation Major diameter E
37、ffective diameter Minor diameter Min. Max. Tol. Min. Max. Tol. Min. in in in in in in in 1 / 4 28 UNF 5 / 16 24 UNF 3 / 8 24 UNF 7 / 16 20 UNF 1 / 2 20 UNF 9 / 16 18 UNF 5 / 8 18 UNF 3 / 4 16 UNF 7 / 8 14 UNF 112 UNF 0.2964 0.3666 0.4291 0.5025 0.5650 0.6347 0.6972 0.8312 0.9678 1.1083 0.2754 0.3421
38、 0.4047 0.4731 0.5357 0.6020 0.6646 0.7945 0.9257 1.0589 0.0022 0.0026 0.0027 0.0031 0.0032 0.0034 0.0035 0.0039 0.0043 0.0047 0.2732 0.3395 0.4020 0.4700 0.5325 0.5986 0.6611 0.7906 0.9214 1.0542 0.2647 0.3289 0.3909 0.4561 0.5182 0.5824 0.6447 0.7716 0.8993 1.0280 0.0070 0.0074 0.0069 0.0078 0.007
39、4 0.0079 0.0077 0.0081 0.0088 0.0100 0.2577 0.3215 0.3840 0.4483 0.5108 0.5745 0.6370 0.7635 0.8905 1.0180 a See note to Clause2. 1 2 3 4 5 6 7 8 Designation Major diameter Effective diameter Minor diameter Min. Max. Tol. Min. Max. Tol. Min. in in in in in in in 1 / 4 5 / 16 3 / 8 7 / 16 1 / 2 9 / 1
40、6 5 / 8 3 / 4 7 / 8 1 1 1 / 8 1 1 / 4 1 3 / 8 1 1 / 2 20 UNC 18 UNC 16 UNC 14 UNC 13 UNC 12 UNC 11 UNC 10 UNC 9 UNC 8 UNC 7 UNC 7 UNC 6 UNC 6 UNC 0.3150 0.3847 0.4562 0.5303 0.5999 0.6708 0.7431 0.8799 1.0193 1.1624 1.3106 1.4356 1.5914 1.7164 0.2863 0.3529 0.4203 0.4890 0.5554 0.6225 0.6903 0.8216
41、0.9543 1.0890 1.2262 1.3514 1.4926 1.6177 0.0038 0.0043 0.0047 0.0051 0.0055 0.0058 0.0062 0.0067 0.0072 0.0078 0.0084 0.0086 0.0094 0.0095 0.2825 0.3486 0.4156 0.4839 0.5499 0.6167 0.6841 0.8149 0.9471 1.0812 1.2178 1.3428 1.4832 1.6082 0.2703 0.3341 0.3985 0.4636 0.5275 0.5918 0.6565 0.7838 0.9124
42、 1.0421 1.1709 1.2959 1.4311 1.5561 0.0095 0.0096 0.0100 0.0106 0.0109 0.0113 0.0118 0.0122 0.0133 0.0150 0.0150 0.0150 0.0200 0.0200 0.2608 0.3245 0.3885 0.4530 0.5166 0.5805 0.6447 0.7716 0.8991 1.0271 1.1559 1.2809 1.4111 1.5361 a See note to Clause2.BS 3409-1:1961 BSI 05-2000 5 Table 4 Limits an
43、d tolerances suitable for tapped holes for inserts for UNF threads, Class 1B a Section 2. Screwing taps 4 General dimensions Recommended dimensions of screwing taps for UNC holes are in accordance withTable 5 and those of screwing taps for UNF holes are in accordance withTable 6. NOTEThese dimension
44、s are in accordance with those specified for standard screwing taps in BS949, “Screwing taps,” but are tabulated here for convenience because the general dimensions of taps are associated with the major diameters of the threads which differ, in the case of the taps covered by the present standard, f
45、rom the nominal major diameters. The tolerances on general dimensions are in accordance withTable 7. 5 Marking Taps for holes intended to receive inserts shall be marked with the designation appropriate to the thread and, in addition, with the words “Wire insert” and the number of this British Stand
46、ard, e.g. 3 / 4 10UNC 2BWire insert. BS3409 1 2 3 4 5 6 7 8 Designation Major diameter Effective diameter Minor diameter Min. Max. Tol. Min. Max. Tol. Min. in in in in in in in 1 / 4 28 UNF 5 / 16 24 UNF 3 / 8 24 UNF 7 / 16 20 UNF 1 / 2 20 UNF 9 / 16 18 UNF 5 / 8 18 UNF 3 / 4 16 UNF 7 / 8 14 UNF 1 1
47、2 UNF 0.2964 0.3666 0.4291 0.5025 0.5650 0.6347 0.6972 0.8312 0.9678 1.1083 0.2765 0.3433 0.4059 0.4744 0.5371 0.6035 0.6661 0.7961 0.9274 1.0608 0.0033 0.0038 0.0039 0.0044 0.0046 0.0049 0.0050 0.0055 0.0060 0.0066 0.2732 0.3395 0.4020 0.4700 0.5325 0.5986 0.6611 0.7906 0.9214 1.0542 0.2647 0.3289
48、0.3909 0.4561 0.5182 0.5824 0.6447 0.7716 0.8993 1.0280 0.0070 0.0074 0.0069 0.0078 0.0074 0.0079 0.0077 0.0081 0.0088 0.0100 0.2577 0.3215 0.3840 0.4483 0.5108 0.5745 0.6370 0.7635 0.8905 1.0180 a See note to Clause2.BS 3409-1:1961 6 BSI 05-2000 Table 5 General dimensions of UNC taps for insert tap
49、ped holes 1 2 3 4 5 6 7 8 9 10 11 Diameter No. of threads per inch No. of flutes Overall length L Length of thread l Diameter of shank d 1 Square Recess Nominal Minimum major Size Length Diameter Length a l 2 d 2 l 1 in mm mm mm mm mm mm mm mm 1 / 4 5 / 16 3 / 8 8.070 9.840 11.664 20 18 16 Left to manufacturers discretion 72 80 85 22 24 25 9.00 10.00 8.00 7.10 8.00 6.30 10 11 9 7.1 7.5 14 15 7 / 16 1 / 2 9 / 16 13.546 15.321 17.122 14
