ASME B18.2.2 pdf download Nuts for General Applications: Machine Screw Nuts, Hex, Square, Hex Flange, and Coupling Nuts (Inch Series)\
3.2 Corner Fill A rounding or lack of fill at junction of hex corners with chamfer shall be permissible, provided the width across corners is within specified limits at and beyond a distance equal to 17.5% of the basic thread diameter from the chamfered face.
3.3 Tops of Nuts and Chamfers Tops of nuts shall be flat and chamfered. Unless other- wise specified by the purchaser or in this Standard, nuts in sizes 5 ⁄ 8 in. nominal size and smaller shall be double- chamfered. Larger size nuts shall be double-chamfered or have washer-faced bearing surface and chamfered top.
3.3.1 Single-Chamfered Nuts and Washer-Faced Nuts. Diameter of the chamfer circle shall be equal to the maximum width across flats within a tolerance of −15%. The length of chamfer at hex corners shall be from 5% to 15% of the basic thread diameter. The surface of the chamfer may be slightly convex or rounded.
3.3.2 Double-Chamfered Nuts. Diameter of the chamfer circle shall be equal to the maximum width across flats with a −10% tolerance.
3.4 Countersink Unless otherwise specified in this Standard, tapped holes shall be countersunk on the bearing faces. The maximumcountersinkdiametershall be the thread basic (nominal) majordiameter plus 0.030 in. for 3 ⁄ 8 in. nominal size nuts and smaller, and 1.08 times the basic major diameter for nuts larger than 3 ⁄ 8 in. No part of the threaded portion shall project beyond the bearing surface.
3.5 Nut Thickness The nut thickness shall be the overall distance, mea- sured parallel to the axis of nut, from the top of the nut to the bearing surface and shall include the thickness of the washer face where provided.
3.6 Washer Face Diameter Unless otherwise specified, the outside diameter of washer face shall be equal to the maximum width across flats with a −10% tolerance.
3.7 Slots When specified in the respective dimensional table, slots shall be normal to nut flats. Contour of bottom of slots shall be at manufacturer’s option. Requirements for gaging slots are specified in Mandatory Appendix I.
3.8 True Position of Tapped Hole
3.8.1 Hex Nuts. The axis of tapped hole in hex nuts shall be located at true position with respect to the axis of nut body within a tolerance zone having a diameter equivalent to 4% of the maximum width across flats for 1 1 ⁄ 2 in. nominal size nuts or smaller and 6% of the maximum width across flats for nuts larger than 1 1 ⁄ 2 in., regardless of feature size.
3.8.2 SquareNuts. The axis oftapped hole insquare nuts shall be located at true position with respect to the axis of nut body within a tolerance zone having a diameter equivalent to 10% of the maximum width across flats, regardless of feature size. 3.9 Bearing Surface Perpendicularity Bearing surface shall be flat and perpendicular to the axis of the threaded hole within the specified full indica- tor measurement (FIM) limit indicated in the tables. See Nonmandatory Appendix C for measurement procedure.
3.10.1 Thread Standard. Threads shall meet the requirements of ASME B1.1.
3.10.2 Thread Class. Unless otherwise specified, threads shall be Unified Standard, Class 2B.
3.10.3 Thread Series. Thread series on nuts may be coarse (UNC), fine (UNF), or 8 thread series (8UN).
3.10.4 Thread Gaging. Unless otherwise specified by the purchaser, gaging for screw thread dimensional acceptability shall be in accordance with Gaging System 21 as specified in ASME B1.3, Screw Thread Gaging Systems for Acceptability.
188.8.131.52 Thread Gaging of Jam Nuts. Due to the three turn allowance and limited number of threads in jam nuts, NOT GO thread plug gages are not a reliable method for thread acceptance. Unless otherwise speci- fied by the purchaser, jam nut thread acceptablity shall be based on acceptance of the GO thread plug gage and nonacceptance of the NOT GO cylindrical plug gage to inspect minor diameter.
3.11 Material Unless otherwise specified by the purchaser or else- where in this Standard, chemical and mechanical prop- erties of steel nuts shall conform to Grade A of ASTM A563, Carbon and Alloy Steel Nuts or Grade 2 (square nuts only) of SAE J995. Nuts of other materials suchas corrosionresistant(stainless) steel, brass, bronze, and aluminum alloys shall have properties as agreed upon between the manufacturer and purchaser. Refer to ASTM F594 for information on corrosion resistant alloy steel requirements and ASTM F467 for information on nonferrous materials.