Machinery's Handbook, 31st Edition
1766 British Fasteners After several years of use of BS 2693:Part 1:1956 (obsolescent), it was recognized that it would not meet the requirements of all stud users. The thread tolerances specified could result in clearance of interference fits because locking depended on the run-out threads. Thus, some users felt that true interference fits were essential for their needs. As a result, the British Standards Committee has incorporated the Class 5 interference fit threads specified in American Standard ASA B1.12 into the BS 2693:Part 2:1964, “Recommendations for High Grade Studs.” British Standard ISO Metric Precision Hexagon Bolts, Screws and Nuts.— This Brit ish Standard BS 3692:1967 (obsolescent) gives the general dimensions and tolerances of precision hexagon bolts, screws and nuts with ISO metric threads in diameters from 1.6 to 68 mm. It is based on the following ISO recommendations and draft recommendations: R 272, R 288, DR 911, DR 947, DR 950, DR 952 and DR 987. Mechanical properties are given only with respect to carbon or alloy steel bolts, screws and nuts, which are not to be used for special applications such as those requiring weldability, corrosion resistance or ability to withstand temperatures above 300 ° C or below − 50 ° C. The dimensional require ments of this standard also apply to nonferrous and stainless steel bolts, screws and nuts. Finish: Finishes may be dull black which results from the heat-treating operation or may be bright finish, the result of bright drawing. Other finishes are possible by mutual agreement between purchaser and producer. It is recommended that reference be made to BS 3382 “Electroplated Coatings on Threaded Components” in this respect. General Dimensions: The bolts, screws and nuts conform to the general dimensions given in Table 3, Table 4, Table 5 and Table 6. Nominal Lengths of Bolts and Screws: The nominal length of a bolt or screw is the distance from the underside of the head to the extreme end of the shank including any chamfer or radius. Standard nominal lengths and tolerances thereon are given in Table 7. Table 7. British Standard ISO Metric Bolt and Screw Nominal Lengths BS 3692:1967 (obsolescent) Nominal Length a l Tolerance Nominal Length a l Tolerance Nominal Length a l Tolerance Nominal Length a l Tolerance 5 ± 0.24 30 ± 0.42 90 ± 0.70 200 ± 0.925 6 ± 0.24 (32) ± 0.50 (95) ± 0.70 220 ± 0.925 (7) ± 0.29 35 ± 0.50 100 ± 0.70 240 ± 0.925 8 ± 0.29 (38) ± 0.50 (105) ± 0.70 260 ± 1.05 (9) ± 0.29 40 ± 0.50 110 ± 0.70 280 ± 1.05 10 ± 0.29 45 ± 0.50 (115) ± 0.70 300 ± 1.05 (11) ± 0.35 50 ± 0.50 120 ± 0.70 325 ± 1.15 12 ± 0.35 55 ± 0.60 (125) ± 0.80 350 ± 1.15 14 ± 0.35 60 ± 0.60 130 ± 0.80 375 ± 1.15 16 ± 0.35 65 ± 0.60 140 ± 0.80 400 ± 1.15 (18) ± 0.35 70 ± 0.60 150 ± 0.80 425 ± 1.25 20 ± 0.42 75 ± 0.60 160 ± 0.80 450 ± 1.25 (22) ± 0.42 80 ± 0.60 170 ± 0.80 475 ± 1.25 25 ± 0.42 85 ± 0.70 180 ± 0.80 500 ± 1.25 (28) ± 0.42 … … 190 ± 0.925 … … a Nominal lengths shown in parentheses are non-preferred. All dimensions are in millimeters. Bolt and Screw Ends: The ends of bolts and screws may be finished with either a 45-degree chamfer to a depth slightly exceeding the depth of thread or a radius approximately equal
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