GMW GMW16457-2011 Non-Propriety (NP) Point for External Metric Thread Coarse Pitch Fasteners Issue 1 English《外部米制螺纹大螺距紧固件的不适当(NP)点 第1次出版(英文版本)》.pdf
《GMW GMW16457-2011 Non-Propriety (NP) Point for External Metric Thread Coarse Pitch Fasteners Issue 1 English《外部米制螺纹大螺距紧固件的不适当(NP)点 第1次出版(英文版本)》.pdf》由会员分享,可在线阅读,更多相关《GMW GMW16457-2011 Non-Propriety (NP) Point for External Metric Thread Coarse Pitch Fasteners Issue 1 English《外部米制螺纹大螺距紧固件的不适当(NP)点 第1次出版(英文版本)》.pdf(3页珍藏版)》请在麦多课文档分享上搜索。
1、 WORLDWIDE ENGINEERING STANDARDS General Specification GMW16457 Non-Propriety (NP) Point for External Metric Thread, Coarse Pitch Fasteners Copyright 2011 General Motors Company All Rights Reserved June 2011 Originating Department: North American Engineering Standards Page 1 of 3 1 Introduction This
2、 point is offered as an alternative to the M point (GMW3362), which is the GM Fastening Engineering approved strategy to prevent cross threading occurrences of externally threaded fasteners. The use of the non-propriety (NP) point style should be limited and must be approved by Fastening Engineering
3、. 1.1 Scope. This standard specifies the characteristics of NP points for external metric threaded fasteners with coarse pitch M5, M6, M8, M10, M12, M14 and M16. 1.2 Designation. Not applicable. 2 References Note: Only the latest approved standards are applicable unless otherwise specified. 2.1 Exte
4、rnal Standards/Specifications. None 2.2 GM Standards/Specifications. GMW3059 GMW16551 GMW3362 3 Requirements 3.1 Dimensions. All dimensions in this standard are given in millimeters (mm) unless otherwise stated. 3.1.1 Nominal Length. The nominal length of the fastener is lnom. For lnom up to, and in
5、cluding 50 mm, the tolerance shall be 0.15. For lnom over 50 mm, the tolerance shall be 0.25. The nominal length, lnom, is the distance, parallel to the fastener axis, from the bearing surface to the lead thread where the thread profile first exceeds 0.2 times the thread pitch in height (measured fr
6、om the thread root). 3.1.2 NP Point Transition Thread Length. The NP point transition threads length, U(ref) is calculated from lnom at an angle of approximately 20 degrees to a point where partial thread ends. 3.1.3 NP Point. The NP point length, Z4, is a minimum/maximum length for the NP point cyl
7、inder. The length of the NP point cylinder shall be measured from the point where the length, lnom, transitions to a point on the cylinder where the end radius is tangent. The diameter of the NP point cylinder, dx, after thread rolling and coating, shall fall within the dimensions as specified in Ta
8、ble 1, for entire NP point length, Z4. The profile of all truncated lead threads shall not exceed maximum condition boundaries of the standard thread. A thread specific “GO” gage shall pass freely over threads after coating (GMW16551). 3.1.4 Point Radius. The radius of this point r, is a minimum dim
9、ension only, and its shape may not be a true radius after threading. The end of the point shall be reasonably perpendicular with the thread axis, and the edge may be irregular. 3.1.5 Point Tip. The tip diameter, dy, is a maximum for the point tip. 3.1.6 Point Length. The overall point length, Z2, is
10、 a maximum length. It represents the sum of the NP point length, Z4 and the NP point thread transition length, U(ref). 3.1.7 Minimum Full Thread Length. The minimum full thread length, leff, is measured from the bearing surface to the last full thread. 3.1.8 Maximum Overall Length. In this standard
11、l1 is a maximum dimension to be used when developing the overall length of the fastener design. The maximum overall (built in) length is the sum of the maximum nominal length (lnom maximum) (3.1.1) and the maximum NP point length (Z4 maximum) (3.1.3). It is the maximum distance from the bearing surf
12、ace to the end of the fastener. 3.2 Material/Mechanical Properties. Per Requirements/Standards associated with the fastener design. 3.3 Surface Treatment. Per Requirements/Standards associated with the fastener design. 3.4 Thread. For external metric coarse thread pitch fasteners in diameters M5, M6
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