ASME B18.2.6M-2012 pdf download
ASME B18.2.6M-2012 pdf download.Metric Fasteners for Use in Structural Applications.
The diameter of chamfer circle on double chamfered nuts and the diameter of washer face shall be within the limits of the maximum width across flats and 95% of the minimum width across flats.
The tops of washer faced nuts shall be flat, and the diameter of the chamfer circle shall be equal to the maximum width across flats with a minus tolerance of 15%. The length of chamfer at hex corners shall be 5% to 15% of the basic thread diameter. The surface of chamfer may be slightly convex or rounded.
Bearing surfaces shall be flat and, unless otherwise specified, shall be perpendicular to the axis of the threaded hole within the total runout (FIM) tabulated for the respective nut size, type, and strength level.
3.1.4 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 faces.
3.1.5 Position of Hexagon to Tapped Hole. At maximum material condition, the nut body shall be located at true position with respect to the thread pitch diameter within a tolerance zone having a diameter equivalent to 4% of the maximum width across the flats.
3.1.6 Countersink. The tapped hole shall be countersunk on the bearing face or faces. The maximum countersink diameter shall be 1.08 times the thread basic (nominal) major diameter. No part of the threaded portion shall project beyond the bearing surface.
3.1.7 Threads. Threads shall be Class 6H in accordance with ASME Bi.13M except when overtapping is required according to para. 3.1.7.2.
3.1.7.1 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.
3.1.7.2 Overtapping. When nuts are zinc coated, either hot dip or mechanical, they shall be overtapped in accordance with the requirements in ASTM A563M.
3.2 Nut Materials
Chemical and mechanical properties of heavy hex nuts shall conform to ASTM A563M property classes.
3.3 Nut Finish
Unless otherwise specified, nuts shall be supplied with a plain (as-processed) finish, unpiated or uncoated. If a finish is required, it shall conform with the applicable finish standard listed in ASTM A563M. The finish on nuts shall be the same type as that designated on and approved for the mating bolts.
4 METRIC HARDENED STEEL WASHERS: ASTM F436M
4.1 Circular and Circular Clipped Washers
4.1.1 Circular and Circular Clipped Washer Dimensions. All circular and circular clipped washers shall conform to the dimensions given in Table 4.
4.1.2 Tolerances. The washer inside diameter, outside diameter, thickness, and edge distance shall be in accordance with Table 4. The deviation from flatness shall not exceed 0.01 mm/mm of outside diameter as the maximum deviation from a straight edge placed on the cut side. The circular runout of the outside diameter with respect to the hole shall not exceed 0.75 mm FIM. Burrs shall not project above the immediately adjacent washer surface by more than 0.25 mm.
4.1.3 Thickness. There are two thicknesses of structural washers: standard and extra thick. Unless otherwise specified by the buyer on the order, the standard thickness shall be supplied.
4.1.4 Washer Finish. Unless otherwise specified, washers shall be supplied with a plain (as-processed) finish. If a finish is required, it shall conform with the applicable finish standard listed in ASTM F436M.
4.1.5 Washer MateriaLs and Mechanical Properties.
Materials and properties shall conform to the requirements specified in ASTM F436M.
