1、BRITISH STANDARD BS 768:1958 Specification for Slotted grub screwsBS768:1958 This British Standard, having been approved by the MechanicalEngineering IndustryStandards Committee and endorsed by the Chairman ofthe Engineering Divisional Council, was published under theauthority of the General Council
2、 on 28 November1958 BSI 03-2000 First published January 1938 First revision November 1958 The following BSI references relate to the work on this standard: Committee reference MEE/60 Draft for comment CX (MEE) 9099 ISBN 0 580358186 Co-operating organizations The Mechanical Engineering Industry Stand
3、ards Committee, under whose supervision this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: Admiralty* High Commission of India* Air Ministry Institute of Marine Engineers Associated Officers Technical
4、 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 Mechanical
5、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 Engi
6、ne Association of Great Britain* Manufacturers Association* Machine Tool Trades Association* British Iron and Steel Federation* Ministry of Labour and National Service British Railways, The British Transport (Factory Inspectorate) Commission* Ministry of Power Crown Agents for Oversea Governments an
7、d Ministry of Supply* Administrations* Ministry of Transport and Civil Aviation D.S.I.R. Mechanical Engineering Research Ministry of Works Laboratory National Coal Board Electricity Council, the Generating Board and National Physical Laboratory (D.S.I.R.)* the Area Boards in England and Wales Radio
8、Industry Council* Engineering Equipment Users Association War Office Gas Council The organizations 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: Agricultural Engineers Association In
9、stitute of Iron and Steel Wire Manufacturers Bright Bolt and Nut Manufacturers Institution of Naval Architects Association Post Office Bright Steel Bar Association Radio Communication and Electronic British Constructional Steelwork Association Engineering Association British Cycle and Motor Cycle In
10、dustries Rolled Thread Screw Association Association Ltd. Screw Manufacturers Association Cold Headed Heat Treated Bolt Association Society of Motor Manufacturers and Council of British Manufacturers of Petroleum Traders Ltd. Equipment Washer Manufacturers Association Electronic Engineering Associat
11、ion Amendments issued since publication Amd. No. Date of issue Comments 1878 January 1976 Indicated by a side line in the marginBS768:1958 BSI 03-2000 i Contents Page Co-operating organizations Inside front cover Foreword ii 1 Scope 1 2 Material 1 3 Terminology 1 4 Dimensions 1 5 Slots 1 6 Length of
12、 screw 1 7 Slotted end 2 8 Types of point 2 9 Screw threads 3 Appendix A Standard lengths of steel and brass grub screws 5 Appendix B Dimensions of grub screws with non-preferred B.S.W. threads 6 Appendix C 7 Figure 1 Alternative types of slotted end 2 Figure 2 Alternative types of point 3 Figure 3
13、Steel grub screws with cup points 7 Table 1 Grub screws with UNC or UNF threads 4 Table 2 Grub screws with B.A. threads 4 Table 3 Grub screws with B.S.W. or B.S.F. threads 4 Table 4 Standard lengths of steel and brass grub screws with unified threads 5 Table 5 Standard lengths of steel and brass gru
14、b screws with B.A. threads 5 Table 6 Standard lengths of steel and brass grub screws with Whitworth threads 6 Table 7 6BS768:1958 ii BSI 03-2000 Foreword This standard makes reference to the following British Standards: BS 84, Parallel screw threads of Whitworth form. BS 93, B.A. screw threads. BS 1
15、580, Unified screw threads. This British Standard has been prepared under the authority of the Mechanical Engineering Industry Standards Committee and forms one of a series for screwed fasteners. When first issued in1938, the standard referred only to dimensions, and related to screws with B.S.W., B
16、.S.F., B.A. and B.S.P.F. (formerly B.S.P.) threads. In revising it to include screws with UNC and UNF threads, the opportunity has also been taken to add provisions for a number of general requirements in accordance with recent British Standards for screwed fasteners. Screws with B.S.P.F. threads ha
17、ve been omitted as there does not appear to be sufficient demand to warrant their inclusion, and hexagon socket set screws are not included as they are now covered by BS2470, “Hexagon socket screws and wrench keys.” In view of the fact that this standard now provides for grub screws with Unified thr
18、eads, every effort has been made to ensure that the dimensions and standard types of points do not conflict with those specified in the American Standard ASA.B18.6.2 1) , although more types of points are included in the latter; there are, however, certain differences in terminology and these are ex
19、plained in Clause3 of the present standard. In accordance with BSI policy concerning the introduction of metric standards, this imperial standard has been declared obsolescent. It will be made obsolete in due course. A British Standard does not purport to include all the necessary provisions of a co
20、ntract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 8, an inside back c
21、over and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. 1) ASA B18.6.2. “Hexagon head cap screws, slotted head cap screws, square head set screws and slotted headless
22、 set screws.”BS768:1958 BSI 03-2000 1 1 Scope This British Standard relates to ferrous and non-ferrous slotted grub screws, having UNC, UNF, B.A., B.S.W. or B.S.F. threads. General dimensions and requirements for material, finish, slots and types of point are given, and tables of standard lengths ar
23、e also included inAppendix A. 2 Material The material from which grub screws are manufactured shall have a tensile strength of not less than the following: If the purchaser requires grub screws to be case-hardened or to be manufactured from steel or brass of a higher tensile strength, or of another
24、material, he shall specify his requirements. NOTEUnless otherwise required by the purchaser, steel grub screws with cup points (seeAppendix C) will be supplied case-hardened. 3 Terminology The designations used in this standard are in accordance with those in common use in British engineering practi
25、ce. It is American practice to use the term “headless set screw,” but the descriptive term “grub screw” is so well established in British engineering that it has been retained for this standard. Radiused points (see Clause8) are shown in the American Standard as “oval” or “round” points. 4 Dimension
26、s The dimensions and tolerances for grub screws shall be as specified in Table 1Table 3 inclusive and Clauses59 inclusive. Point dimensions for grub screws with cup points are given inAppendix C. 5 Slots The slots shall be clean and reasonably free from burrs, and, on visual inspection, shall appear
27、 to pass through the centre point of the surface plane of the top of screw. The depth of slot (Dimension B, Figure 1) shall be measured from the extreme end of the screw to the point at which the slot breaks through. 6 Length of screw For the purposes of this standard the “length” shall be the dista
28、nce between the extreme ends of the screw, whatever the type of point. The permissible tolerance on length shall be as follows: NOTE 1Attention is drawn to the fact that the tolerances on length are expressed in a negative direction. NOTE 2Standard lengths are given in Table 4, Table 5 and Table 6 i
29、n Appendix A. Steel 25 tons/sq. in. Brass 20 tons/sq. in. Length Major diameter of thread Tolerance on length in. in. in. Up to and including 1 / 8 All diameters + 0 0.01 Above 1 / 8up to and including 1 / 2 Below 1 / 4 1 / 4and over + 0 0.02 + 0 1 / 32 Above 1 / 2 up to and including 1 All diameter
30、s + 0 1 / 32 Above 1 up to and including 2 All diameters + 0 1 / 16 Over 2 All diameters + 0 3 / 32 BS768:1958 2 BSI 03-2000 7 Slotted end The slotted end may, at the option of the manufacturer, be finished with either a flat chamfer with a90 included angle to a depth slightly exceeding the depth of
31、 thread, or with a radius approximately equal to the nominal diameter of the screw thread D (seeFigure 1). This option shall apply unless the purchaser in his enquiry and order specifically states that he requires screws with “flat chamfered” or “radiused” slotted ends. NOTEAttention is drawn to the
32、 fact that these alternative slotted ends are associated with the particular method of manufacture. A request by the purchaser for a specific type of slotted end limits the manufacturing processes available, and it is therefore recommended that the purchaser avoids making such a request unless circu
33、mstances fully justify it. 8 Types of point a) General. The standard types of points at the unslotted end shall be the cone point and the radiused point, as shown inFigure 2. The cup point, which is shown inAppendix C is not normally used and will be supplied only when specially ordered. The preferr
34、ed type of point for steel grub screws with B.S.W., B.S.F., UNC or UNF threads is the cone point. The preferred type of point for brass grub screws with any of the standard thread forms, and for steel grub screws with B.A. threads is the radiused point. Unless otherwise specified by the purchaser, t
35、hese preferred types of points shall be supplied. b) Cone points. For grub screws with a length equal to or less than the basic major diameter of the thread, the cone point shall have an included angle of120 . For grub screws with a length greater than the basic major diameter of the thread, the con
36、e point shall have an included angle of90 . c) Radiused points. Radiused points shall have a radius approximately0.75times the basic major diameter of the thread. Figure 1 Alternative types of slotted endBS768:1958 BSI 03-2000 3 9 Screw threads Grub screws shall, for their full screwed length, have
37、their screw threads in accordance with the limits and tolerances laid down in the appropriate British Standard as follows: Other classes of fit are not normally supplied. They should be ordered only in exceptional circumstances and, if required, shall be specified by the purchaser in his enquiry and
38、 order. Figure 2 Alternative types of point BS 1580 “Unified screw threads” Class 2A BS 93 “B.A. screw threads” Normal class BS 84 “Parallel screw threads of Whitworth form” Medium classBS768:1958 4 BSI 03-2000 Table 1 Grub screws with UNC or UNF threads Table 2 Grub screws with B.A. threads Table 3
39、 Grub screws with B.S.W. or B.S.F. threads NOTEDimensions for grub screws of 5 / 32in. nominal size are given in Appendix B. 1 2 3 4 5 Nominal size Basic major diameter of thread D Width of slot A (Figure 1) Depth of slot B (Figure 1) Max. Min. Nom. in. in. in. in. in. 1 / 4 5 / 16 3 / 8 0.250 0 0.3
40、12 5 0.375 0 0.056 0.063 0.077 0.045 0.051 0.064 0.063 0.078 0.094 7 / 16 1 / 2 9 / 16 0.437 5 0.500 0 0.562 5 0.085 0.096 0.107 0.072 0.081 0.091 0.109 0.125 0.141 5 / 8 3 / 4 0.625 0 0.750 0 0.119 0.147 0.102 0.129 0.156 0.188 1 2 3 4 5 6 Nominal size Basic major diameter of thread D Width of slot
41、 A (Figure 1) Depth of slot B (Figure 1) Max. Min. Nom. mm in. in. in. in. 0 1 2 6.0 5.3 4.7 0.236 2 0.208 7 0.185 0 0.048 0.044 0.040 0.040 0.036 0.032 0.063 0.059 0.055 3 4 5 4.1 3.6 3.2 0.161 4 0.141 7 0.126 0 0.036 0.032 0.029 0.029 0.025 0.023 0.051 0.047 0.043 6 7 8 2.8 2.5 2.2 0.110 2 0.098 4
42、 0.086 6 0.026 0.023 0.021 0.020 0.017 0.015 0.039 0.036 0.033 9 10 12 1.9 1.7 1.3 0.074 8 0.066 9 0.051 2 0.019 0.017 0.015 0.013 0.012 0.010 0.030 0.027 0.024 1 2 3 4 5 Nominal size Basic major diameter of thread D Width of slot A (Figure 1) Depth of slot B (Figure 1) Max. Min. Nom. in. in. in. in
43、. in. a1 / 8 3 / 16 1 / 4 0.125 0 0.187 5 0.250 0 0.029 0.040 0.056 0.023 0.032 0.045 0.043 0.055 0.063 5 / 16 3 / 8 7 / 16 0.312 5 0.375 0 0.437 5 0.063 0.077 0.085 0.051 0.064 0.072 0.078 0.094 0.109 1 / 2 9 / 16 5 / 8 0.500 0 0.562 5 0.625 0 0.096 0.107 0.119 0.081 0.091 0.102 0.125 0.141 0.156 3
44、 / 4 0.750 0 0.147 0.129 0.188 a Standard with B.S.W. threads only.BS768:1958 BSI 03-2000 5 Appendix A Standard lengths of steel and brass grub screws The sizes listed inTable 4, Table 5 and Table 6 are those which are expected to be in greatest demand, and include those preferred sizes (marked P) w
45、hich are most likely to be stocked in steel when the standard comes into general use. It is therefore recommended that purchasers should order these sizes whenever possible. Sizes marked X will not normally be stocked. Intermediate lengths not shown in these tables should be avoided. Table 4 Standar
46、d lengths of steel and brass grub screws with unified threads NOTE 1Steel grub screws with UNF threads are not expected to be normally stocked, but should be ordered to the standard lengths given above. NOTE 2Brass grub screws with UNC and UNF threads are not expected to be normally stocked except i
47、n the shorter lengths of 1 / 4 in. diameter UNC but should be ordered to the standard lengths given above. NOTE 3Unless otherwise specified by the purchaser, steel grub screws with UNC and UNF threads will be supplied with Cone points and brass grub screws with UNC and UNF threads will be supplied w
48、ith radiused points (see Clause8). Table 5 Standard lengths of steel and brass grub screws with B.A. threads NOTE 1The first choice preferred sizes marked P1 are those most likely to be obtained from stock. There may be more difficulty in obtaining from stock the second choice preferred sizes marked
49、 P2. NOTE 2B.A. grub screws are normally stocked both in steel and brass. Length in inches Diameters 1 / 4UNC 5 / 16UNC 3 / 8 UNC 7 / 16UNC 1 / 2 UNC 5 / 8 UNC 3 / 4 UNC 1 / 4 5 / 16 3 / 8 P P P P P P P 1 / 2 5 / 8 3 / 4 P P P P P P P P P P X P P P P X X 7 / 8 1 1 1 / 4 P P P P P P P P P X X X X P P X X X X X X 1 1 / 2 1 1 / 2 2 X X X X X X P X X X X X P X X X X X X X X Length in inches B.A. sizes 0 1 2 3 4 5 6 7 8 9 10 12 1 / 16 3 / 32 1 / 8 X P1 X
