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
13、, M8, M10, M12, M14 and M16. 3.5 Tolerances. Tolerances as specified in Table 1 for NP point. All non-specified tolerances follow Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,
14、-,-GM WORLDWIDE ENGINEERING STANDARDS GMW16457 Copyright 2011 General Motors Company All Rights Reserved June 2011 Page 2 of 3 that of the Requirements/Standards associated with the fastener design. 3.6 Surface Discontinuities. Follow requirements of the standards associated with the fastener design
15、. 3.7 Proof Load Requirements. Not applicable. 3.8 Acceptability. As specified in Table 1 for NP point. All non-specified tolerances follow that of the Requirements/Standards associated with the fastener design and tolerancing.Figure 1: Dimensional Illustration Table 1: Dimensions Note 1 Thread M5 M
16、6 M8 M10 M12 M14 M16 Z2 maximum 6 7 9 11 13 15 17 Z4 maximum minimum 3.9 3.4 4.5 4 6 5.5 7.6 7.1 9 8.5 10.5 10 12.6 12.1 dx After thread rolling maximum minimum 4.12 3.97 4.90 4.77 6.62 6.49 8.36 8.21 10.09 9.91 11.82 11.67 13.82 13.67 dy maximum 3 4 5.5 7 8.5 10 11.5 r minimum 0.3 0.5 1 1.5 2 2.5 3
17、 U(ref) reference 2.6 3 3.5 3.9 4.5 5 4.9 Note 1: All dimensions are in millimeters (mm) 4 Rules and Regulations 4.1 Legal Regulations. All materials must satisfy applicable laws, rules, regulations and recommendations valid in the country of usage. 4.2 Language. In the event of conflict between the
18、 English and domestic language, the English language shall take precedence. 4.3 Inspection and Rejection. Samples of components or materials released to a GM general Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking
19、permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW16457 Copyright 2011 General Motors Company All Rights Reserved June 2011 Page 3 of 3 specification shall be tested for conformity with the requirements of this general specification and approved by the responsible Engineer
20、ing department prior to commencement of delivery of bulk supplies. A new approval must be received for any changes, e.g., properties, manufacturing process, location of manufacture, etc. If not otherwise agreed, all testing and documentation normally required for initial release must be completed. I
21、t is the responsibility of the supplier to inform the customer in a timely manner, without solicitation, and to include documentation of all modifications of materials and/or processes and to apply for a new release. If not otherwise agreed, all release tests shall be repeated and documented by the
22、supplier prior to commencement of delivery of non-conforming bulk supplies. In individual cases, a shorter test can be agreed to between the responsible Engineering department and the supplier. 4.4 Initial Source Approval. Not applicable. 4.5 All materials supplied to this standard must comply with
23、the requirements of GMW3059, Restricted and Reportable Substances for Parts. 5 Approved Sources Not applicable. 6 Notes 6.1 Glossary. Not applicable. 6.2 Acronyms, Abbreviations, and Symbols. NP Non-propriety 7 Coding System This standard shall be referenced in other documents, drawings, etc., as fo
24、llows: GMW16457 8 Release and Revisions This standard was originated in November 2010. It was first approved in May 2011. It was first published in June 2011. Issue Publication Date Description (Organization) 1 JUN 2011 Initial publication. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
