Find the most up-to-date version of BS at Engineering BRITISH STANDARD OBSOLESCENT AUGUST BS Incorporating Amendment Nos. 1, 2 and 3 Specification for Licensed. Standard. Line Drawing. Product Description. DIN HEXAGON FULL NUT. 70 . BS HEXAGON FULL NUT BSW. BS

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DATE, Uncontrolled Copy, c BSI The Government departments and scientific and industrial 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: BSI Licensed Copy: BS 18, Methods for tensile testing of metals.

BSMethods for notched bar tests — Part 1: The Izod impact test on metals. BSMethods of Brinell hardness test — Part 1: BSTable of approximate comparison of hardness scales. BSScrew gauge limits and tolerances — Part 1: Gauges for screw threads of Unified form. BSPlain limit gauges: BSSpecification for wrought steels for mechanical and allied engineering purposes — Part 1: General inspection and testing procedures and specific requirement for carbon, carbon manganese, alloy and stainless steels.

BSSplit cotter pins. BSUnified screw threads — Parts 1 and 2: BSSpecification for steel wire for cold forged fasteners and similar components — Part 1: Carbon and low alloy steel. When BS was first issued inits publication marked an important stage in the development of the Unified screw thread system established in accordance with the agreement reached by the United Kingdom with the United States and Canada at the Ottawa Conference of and ratified by the Declaration of Accord signed by representatives of those three countries in November, It was recognized at that time that effective adoption of the system depended very largely on the provision of commonly used types and sizes of fasteners, the general features of which would be unified as well as the threads.

As a first step, two standards for hexagon bolts, screws and nuts were published: BS was restricted at that time to sizes up to and including 1 inch but the many requests received for an extension of the standard have long indicated that this range was inadequate for the needs of industry and this edition accordingly provides for sizes up to and including 2 inches. It should be mentioned that this extension of the Unified range is also in accordance with agreement reached with the U. In revising the standard, the opportunity has been taken to deal more fully with material and manufacture.

In addition to specifying materials for cold forged bolts, screws and nuts and offering guidance in the selection of materials for those produced by other methods, the standard now includes full details of the tests to be employed for determining the mechanical properties of the fasteners. Reference is also made to the control of decarburization and rolling laps. It is recognized that a transition period will necessarily ensue during which stocks of both grades will be held by manufacturers and either may be offered when bolts in this tensile range are ordered.

Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations.

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. The dimensional requirements of this standard apply both to ferrous and non-ferrous bolts, screws and nuts. Mechanical properties are given only in respect of steel bolts, screws and nuts, and the finishes in which they are normally supplied are described in Clause 3.

NOTE It is considered that the range of nominal sizes included in this standard is adequate for most of the applications for which this series is likely to be employed, but for the convenience of users requiring larger sizes, the formulae from which the proportions for bolt heads and nuts are derived stanrard given in Appendix Standarrd. In order to provide for the standare methods of manufacture by which bolts, screws and nuts to this standard may be produced, a choice of materials is given.

Bolts, screws and nuts can also be produced by machining from hexagon bars. Bolts and screws produced by cold stnadard shall, except in the case of bolts and screws bright finished to Grade A see Table 4, Appendix A be heat-treated after forging.

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Bolts, screws and nuts produced by hot forging or by turning from bars, and cold formed nuts shall be heat-treated standqrd this etandard necessary to give the requisite mechanical properties specified in Clauses 4 and 6 and Appendix A.

Cold forged bolts and screws. The choice of material used to gs1768 bolts and screws by cold forging shall normally be at the discretion of the manufacturer. The finished products shall comply with the requirements for physical properties as set out in Clause 4 and in Table 4 of Appendix A.

If, however, the purchaser wishes to specify the composition of the material to be used, this shall be the subject of agreement with the manufacturer. Cold forged nuts and hot forged bolts, screws and nuts.

BS 1768:1963

The material to be used for cold forged nuts or hot forged bolts, screws and bs7168 depends to a large extent on the size of the product. Unless otherwise stipulated by the purchaser, the choice of material shall therefore be left to the manufacturer provided that the finished products satisfy the requirements for mechanical properties set out in Clauses 4 and 6 and in Table 4 and Table 6 of Appendix A, but recommendations on suitable materials are given for guidance in Table 8 and Table 10 of Appendix B.

Bolts, screws and nuts machined from bars.

Table 9 and Table 10 of Appendix B give a selection of steels from BS which are among those suitable for particular grades of bolts, screws and nuts.

Unless otherwise stipulated by the purchaser, the choice of material shall be left to the manufacturer provided that the finished products satisfy the requirements for mechanical properties set out in Clauses 4 and 6 and in Table 4 and Table 6 of Appendix A. As normally manufactured from wire of ordinary quality, a proportion of threads produced on forged bolts and screws by rolling may have some surface decarburization principally at crests of threads.

For highly stressed bolt applications, the definition and degree of such decarburization shall be negotiated between manufacturer and user. For bolts of strength Grade T and greater, the depth of decarburization, measured from the crest, shall not exceed 33 per cent of the height of the threads.

Complete freedom from any decarburization is achieved by shank grinding after heat treatment and before thread rolling; if this is required, it shall be the subject of negotiation between manufacturer and user. When threads are produced by rolling, small laps are commonly present at the crests and are generally of a stxndard which is not detrimental to the performance of the bolt.

A lap formed at the crest of the thread perpendicular to the axis of the bolt shall standdard be considered a cause for rejection if the depth of the lap does not exceed 33 per cent of the depth ns1768 the thread. Bolts of Grades T, V and X shall be free from laps in the thread flank below the effective diameter. Laps in the flanks above the effective diameter shall not have a depth greater than 33 per cent of the thread atandard. The bolts, screws and nuts shall be cleanly finished, sound and free from defects.

Steel precision bolts, screws and nuts are normally supplied with the following finishes: The surfaces of these bolts and screws are customarily dull black from heat treatment, although the manufacturer may machine some of the surfaces of the larger size bolts and screws after heat treatment. B1768 term is used to describe bolts and screws which are machined on all surfaces or which have a finish on the hexagons produced by bright drawing and regarded as a machined finish.

These may be bright on all surfaces or dull black where heat treated. If steel bolts, screws or nuts are required bright all over, the purchaser should state this in his enquiry and order. If the purchaser requires bolts, screws or nuts of steel or other material to be coated, he should state the type of coating required in his enquiry and order.

Tensile strength and proof stress. The tensile strength and the proof stress shall be determined by stajdard methods of test described in Clause 5. They shall be tested in accordance with the standard procedure as given in BS Area; BS 18 now specifies a gauge length of 5. Area, but values appropriate to this length are not yet available for the higher grades of steel. The former gauge length and its associated values have therefore been retained in this standard for the time being and a suitable amendment will be issued when the necessary information can be supplied.

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Minimum Izod impact value. Where an Izod test is not practicable, a nicked fracture test may be substituted. A hardness test on bolts and screws is not part of the requirements of this standard, but Brinell hardness values are given for guidance in Table 4 of Appendix A. The tensile test on a bolt or screw shall be carried out as follows: An ordinary nut or its equivalent in the form of an adaptor shall be screwed on to the bolt or screw so as to be clear of the run-out of the thread towards the head and also clear of any imperfect threads at the point, the load shall then be applied to the head and to the nut or adaptor.

The proof stress for bolts shall be determined as follows: The proof stress for bolts or screws shall be determined with a straight full size threaded bolt or screw. The bolt or screw shall be placed in a suitable testing machine with the threaded end of the bolt or screw in a threaded grip or in a nut.

The grips of the testing machine shall be self-aligning to avoid side thrust see Figure 16 in Appendix C. The bolt or screw shall be subjected to the proof stress for bolts and screws specified in Column 3 of Table 4 in Appendix A by applying the appropriate load as given in Table 5, Appendix A and maintaining for ten seconds and then releasing.

BS 1768-1963 Unified hexagon head screws, washer faced

Measurement of the specimens subjected to the proof stresses for bolts or screws shall be performed in the following manner: The overall length of the bolt or screw shall be measured at its true centre line with an instrument capable of measuring changes in length of 0. After the bolt or screw has been stressed in accordance with the provisions of i of this clause, its length shall again be measured. NOTE The preferred method of carrying out this test is to measure the sgandard between conical centres on the centre line of the bolt or screw which has been set up on the mating centres of the anvils of the measuring fixture; the head or shank of the bolt or screw atandard be marked so that it can be placed in the same position for all measurements.

Nuts shall be graded as follows: Nuts suitable for use with bolts, Grades A, B and P. The nuts shall be capable of withstanding a proof load, based on the minimum tensile strength of Grade P Bolts, as laid down in Table 4, Column 2. Nuts suitable for use with Bolts Grade S. These nuts shall be capable of withstanding a proof load, based on the minimum tensile strength of Grade S Bolts, as laid down in Table 4, Column 2.

BS Unified hexagon head screws, washer faced

Nuts suitable for use with Bolts Grade T. These nuts shall be capable of withstanding a proof load, based on the minimum tensile strength of Grade T Bolts, as laid down in Table 4, Column 2. Nuts suitable for use with Bolts Grades V and X. These nuts shall be capable of withstanding a proof load, based on the minimum tensile strength of Grade X Bolts, as laid down in Table 4, Column 2.

Nuts 1 in diameter and under. These nuts shall meet the requirements for proof load specified in Table 6. They shall be tested in accordance with the method described in Clause 7. Nuts over 1 in diameter. As equipment of sufficient capacity may not be readily available for nuts in this range, they shall meet the requirements for hardness specified in sub-clause c below. Nuts of diameters over 1 in shall be subjected to a hardness test and their hardness shall not be less than that specified below: For nuts up to and including 1 in diameter, a hardness test is not part of the requirements of this standard but for general guidance Brinell hardness values are given below: Birnell Hardness Licensed Copy: The test shall be made on the end faces of the nuts.