Machinery's Handbook, 31st Edition
1768
British Fasteners % R
10 1 minimum tensile strength stressat permanent set limit 0.2 = the numerical values of stress and strength being obtained from the accompanying table. Strength Grade Designations of Steel Bolts and Screws Strength Grade Designation 4.6 4.8 5.6 5.8 6.6 6.8 8.8 10.9 12.9 14.9 Tensile Strength ( R m ), Min. 40 40 50 50 60 60 80 100 120 140 Yield Stress ( R e ), Min. 243230403648………… Stress at Permanent Set Limit ( R 0.2 ), Min. … … … … … … 64 90108126 All stress and strength values are in kgf/mm 2 units. 80 64 1 100 # # Strength Grade Designation System for Steel Nuts: The strength grade designation sys tem for steel nuts is a number which is one-tenth of the specified proof load stress in kgf/ mm 2 . The proof load stress corresponds to the minimum tensile strength of the highest grade of bolt or screw with which the nut can be used. Strength Grade Designations of Steel Nuts Strength Grade Designation 4 5 6 8 12 14 Proof Load Stress (kgf/mm 2 ) 40 50 60 80 120 140 Recommended Bolt and Nut Combinations Grade of Bolt 4.6 4.8 5.6 5.8 6.6 6.8 8.8 10.9 12.9 14.9 Recommended Grade of Nut 445566812 12 14 Note: Nuts of a higher strength grade may be substituted for nuts of a lower strength grade. Marking: The marking and identification requirements of this Standard are only manda tory for steel bolts, screws and nuts of 6 mm diameter and larger; manufactured to strength grade designations 8.8 (for bolts or screws) and 8 (for nuts) or higher. Bolts and screws are identified as ISO metric by either of the symbols “ISO M” or “M”, embossed or indented on top of the head. Nuts may be indented or embossed by alternative methods depending on their method of manufacture. Designation: Bolts 10 mm diameter, 50 mm long manufactured from steel of strength grade 8.8, would be designated: “Bolts M10 × 50 to BS 3692.—8.8.” Brass screws 8 mm diameter, 20 mm long would be designated: “Brass screws M8 × 20 to BS 3692.” Nuts 12 mm diameter, manufactured from steel of strength grade 6, cadmium plated could be designated: “Nuts M12 to BS 3692.—6, plated to BS 3382: Part 1.” Miscellaneous Information: The Standard also gives mechanical properties of steel bolts, screws and nuts [i.e., tensile strengths; hardnesses (Brinell, Rockwell, Vickers); stresses (yield, proof load); etc.], material and manufacture of steel bolts, screws and nuts; and information on inspection and testing. Appendices to the Standard give information on gaging; chemical composition; testing of mechanical properties; examples of marking of bolts, screws and nuts; and a table of preferred standard sizes of bolts and screws, to name some.
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