ASME B18.3-2012 pdf – Socket Cap, Shoulder, Set Screws, and Hex Keys (Inch Series)
ASME B18.3-2012 pdf – Socket Cap, Shoulder, Set Screws, and Hex Keys (Inch Series).
(12) Edge oil-lead. The edge between the bearing surface and the side of the head may be broken (rounded or chamfered), but the radius or chamfer measured along the bearing surface shall not exceed the values listed for K.
(13) Bearing Surface. The plane of the bearing surface shall be perpendicular to the axis of the shank, within a maximum deviation of 1 deg, obtained by holding the screw on the body or major thread diameter within I diameter of the bearing surface of the head, but beyond the maximum length of the fillet, FL, and inspecting on an optical comparator, or comparable inspection equipment, rotating the axis of the shank 360 deg.
(14) Body. The term body refers to the unthreaded cylindrical portion of the shank for those screws not threaded to the head.
(15) See Table 18 for hexagon socket dimensions and Mandatory Appendix I for gaging of hexagon sockets.
(a) The runout of the head with the axis of the shank shall be within 2% of the maximum basic screw diameter dimension, D, or 0.006 in., whichever is greater.
Runout for (a) above is defined as the full indicator movement (ElM) obtained by holding the screw on the body or major screw thread diameter within 1 diameter of the bearing surface of the head, but beyond the maximum length of the fillet, F1, rotating 360 deg and indicating on the outside diameter of the head.
(b) The runout of the socket with the axis of the shank of the screw shall be within 3% of the maximum screw diameter, 0, or 0.005 in., whichever is greater for nominal sizes through 1/2 in. diameter and 6% for nominal sizes above 1/2 in. diameter.
Runout for (b) above is defined as the full indicator movement (FIM) obtained by holding the screw on the body or major screw thread diameter within I diameter of the bearing surface of the head, but beyond the maximum length of the fillet, FL, rotating 360 deg, indicating on each of six hexagon flats.
(c) The conformance of screws to shank straightness or camber limitations set forth as De in Table 6, shall be checked by the use of the procedures and typical gage illustrated in ASME B18.2.9.
(17) Threads. Threads shall be Unified external threads with radius root: Class 3A UNRC and UNRF Series for screw sizes 0 (0.060 in.) through 1 in.; Class 2A UNRC and UNRE Series for sizes over 1 in. to 11/2 in., inclusive; and Class 2A UNR Series for sizes larger than 11/2 in.
For plated or unplated screws, acceptability shall be based upon System 22, ASME B1.3.
Class 3A does not provide a plating allowance.
(a) Steel, Alloy. Cap screws shall be fabricated from an alloy steel and shall conform in all respects to ASTM A574.
(b) Steel, Corrosion-Resistant. Cap screws shall be fabricated from a corrosion-resistant steel and shaLl conform to ASTM F837.
(19) Surface Roughness. For alloy steel screws of sizes up to and incuding % in., and nominal lengths equal to or less than 8 times the basic screw diameter, the surface roughness of the screws shall not exceed 63 i.in. (arithmetical average) on the fillet and head bearing surfaces, nor exceed 32 lJ.in. (arithmetical average) on the threads.
For larger sizes, longer lengths, and corrosion-resistant steel screws, the surface roughness of the screws shall not exceed 125 jj.in. (arithmetical average) on the body [see Note (8)], fillet [see Note (14)], and head bearing surfaces.
Normally, it shall be sufficient to ascertain that these surfaces on screws have the equivalent of a smooth machined finish by visual comparison with known surface standards. However, where it is practical and deemed necessary to measure these surfaces with commercially available equipment, roughness measurements shall be taken axially on the body and fillet surfaces, and circumferentially on the bearing surface. (See ASME B46.1, Surface Texture.)
(20) Drawings. On socket screw drawings, when the distance from the bearing surface of the head to the threading is dimensioned, regardless of type of thread representation (see ASME Y14.6 for description of schematic and simplified thread representation), the dimension should be noted to indicate whether body length or grip length is required.
(21) Designation. To promote uniformity and understanding in communications relating to products conforming to this Standard, it is recommended that Hexagon Socket Head Cap Screws be designated in accordance with the following data, preferably in the sequence shown:
(a) product name
(b) designation of the standard
(c) nominal size (number, fractional or decimal equivalent)
(d) thread pitch
(e) nominal length (fractional or decimal equivalent)
(g) protective finish, if required
Hexagon Socket Head Cap Screws, ASME B18.3, 6-32 x 3/4, Alloy Steel
For the recommended B18 part identifying numbering system (PIN), see ASME B18.24.