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Large Hex Head Tapping Screws
Tapping Screws
- Where specifying nominal size in decimals, zeros preceding decimal and in the fourth decimal place shall be omitted.
- Applicable to screw types as indicated by code symbols.
Type AB thread forming.
Types B and BP thread forming and Types BF and BT thread cutting.
Type C thread forming, Appendix; and Types D, F, G, and T thread cutting. - A slight rounding of all edges and corners of the hex surfaces of indented hex heads shall be permissible, provided the diameter of the bearing circle is equal to no less than 90% of the specified minimum width across flats dimension.
- Unless otherwise specified by purchaser, regular hex heads shall be furnished, and both regular and large head styles may be of indented head, trimmed head, or fully upset head construction, at the option of manufacturer.
- Dimensions across flats and across corners of the head shall be measured at the point of maximum metal. Taper of sides of hex (angle between one side and the axis) shall not exceed 2° or 0.004", whichever is greater, the specified width across flats being the large dimension.
- The rounding due to lack of fill on all six corners of the head shall be reasonably uniform and the width across corners of the head shall be such that when a sharp ring having an inside diameter equal to the specified minimum width across corners is placed on the top and bottom of the head, the head shall protrude by an amount equal to, or greater than, the F value tabulated. See Appendix II for across corners gaging of hex heads.
- Large hex head is intended for screw and washer assemblies - SEMS, as specified in ASME B18.1 and other applications requiring large bearing.
