Machinery's Handbook, 31st Edition
1826 Socket Screws British Standard Hexagon Socket Screws—Metric Series.— The first five parts of Brit - ish Standard BS 4168: 1981 provide specifications for hexagon socket head cap screws and hexagon socket set screws. Hexagon Socket Head Cap Screws: The dimensional data in Table 1 are based upon BS 4168: Part 1: 1981. These screws are available in stainless steel and alloy steel, the latter having class 12.9 properties as specified in BS 6104:Part 1. When ordering these screws, the designation “Hexagon socket head cap screw BS 4168 M5 × 20-12.9” would mean, as an example, a cap screw having a thread size of d = M5, nominal length l = 20 mm, and property class 12.9. Alloy steel cap screws are furnished with a black oxide finish (thermal or chemical); stainless steel cap screws with a plain finish. Combinations of thread size, nominal length, and length of thread are shown in Table 2; the screw threads in these com binations are in the ISO metric coarse pitch series specified in BS 3643 with tolerances in the 5g6g class. (See Metric Screw Threads in Index.) Hexagon Socket Set Screws: Part 2 of BS 4168:1981 specifies requirements for hexagon socket set screws with flat point having ISO metric threads, and diameters from 1.6 mm up to and including 24 mm. The dimensions of these set screws along with those of cone- point, dog-point, and cup-point set screws in accord, respectively, with Parts 3, 4, and 5 of the Standard are given in Table 3 and the accompanying illustration. All of these set screws are available in either steel processed to mechanical properties class 45H BS 6104:Part 3; or stainless steel processed to mechanical properties described in BS 6105. Steel set screws are furnished with black oxide (thermal or chemical) finish; stainless steel set screws are furnished plain. The tolerances applied to the threads of these set screws are for ISO product grade A, based on ISO 4759 ∕ 1-1978 “Tolerances for fasteners.—Part 1: Bolts, screws, and nuts with thread diameters greater than or equal to 1.6 mm and less than or equal to 150 mm and product grades A, B, and C.” Hexagon socket set screws are designated by the type, the thread size, nominal length, and property class. As an example, for a flat-point set screw of thread size d = M6, nominal length l = 12 mm, and property class 45H: Hexagon socket set screw flat point BS 4168 M6 × 12-45H British Standard Hexagon Socket Countersunk and Button Head Screws.—Metric Series: British Standard BS 4168:1967 provides a metric series of hexagon socket countersunk and button head screws. The dimensions of these screws are given in Table 4 . The revision of this Standard will constitute Parts 6 and 8 of BS 4168. British Standards for Mechanical Properties of Fasteners: BS 6104: Part 1:1981 spec ifies mechanical properties for bolts, screws, and studs with nominal diameters up to and including 39 mm of any triangular ISO thread and made of carbon or alloy steel. It does not apply to set screws and similar threaded fasteners. Part 2 of this Standard specifies the mechanical properties of set screws and similar fasteners, not under tensile stress, in the range from M1.6 up to and including M39 and made of carbon or alloy steel. BS 6105:1981 provides specifications for bolts, screws, studs, and nuts made from aus tenitic, ferritic, and martensitic grades of corrosion-resistant steels. This Standard applies only to fastener components after completion of manufacture with nominal diameters from M1.6 up to and including M39. These Standards are not described further here. Copies may be obtained from the British Standards Institution, 389 Chiswick High Road, London, W4 4AL, www.bsigroup.com, and also from the American National Standards Institute, 25 West 43rd Street, New York, NY 10036, www.ansi.org.
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