WORLDWIDE ENGINEERING General Specification GMWw3362 Pav ey Nal oh) M Point for External Metric Thread, Coarse Pitch Fasteners 1 Introduction Note: Nothing in this standard supercedes applicable laws and regulations Note: In the event of conflict between the English and domestic language, the English language shall take precedence. 1.1 Purpose. This standard specifies the characteristics of M Points for external metric threaded fasteners with coarse pitch; M4, M5, M6, M8, M10, M12, M14, M16, M18 and MZO. 4.4.1 Designation, Type A: Bolts, sorews, studs and double end studs with a standard end point, see Figure 1 and Table 1. Type B: Bolts, screws and double end studs with an external hex driver end point, see Figure 2 and Table 2. Type C: Bolts, screws and double end studs with an external six-lobe driver end point, see Figure 3 and Table 3. Note: When not expiicitly specified, the default shall be Type A. 1.2 Applicability. This specification applies to the design of an anti-cross threading feature for extemally threaded fasteners. Note: Only the latest approved standards are applicable unless otherwise spe 1.3 Remarks. Not applicable. 6. 2 References Note: Only the latest approved standards are applicable unless otherwise specified, 2.1 External Standards/Specifications. None 2.2 GM Standards/Specifications. GMw3059 2.3 Additional References. None 3 Requirements 3.1 Dimensions. All dimensions in this standard are given in millimeters (mm) unless otherwise stated. 3.1.1 Length. For fasteners of Nominal Thread Length (Lnom) < §0 mm, the tolerance, T, shall be + 0.15 mm, For fasteners of Nominal Thread Length (Lnom) > 50 mm, the tolerance, T, shall be + 0.25 mm. The nominal length is calculated from the required full thread length or the maximum overall length required of the fastener {or the joint. The nominal length is the distance parallel to the fastener axis from the bearing surface or datum surface (example: end of the shoulder on a shoulder bolt) to the lead thread where the thread profile approximates 0.20x the thread pitch in height (measured from the thread root). 3.1.2 M Point Thread. The M Point thread length, U, is a reference dimension used for calculation purposes. The profile ofall lead threads shall not exceed maximum material condition boundaries of the standard thread. At least one (1) complete turn (360 degrees) of the first two (2) threads shall be smoothly and uniformly curved for its entire profile with no localized scallops, fissures, underfil, flats or other discontinuities permitted at the Crest of the thread. A thread specific GO screw ring gauge shall pass freely over first four (4) threads ater coating. © Gopyrght 2019 General Motors Gampary All Fights Reserved April 2019 Page 1 of 5GM WORLDWIDE ENGINEERING STANDARDS GMW3362 3.1.3 Dog Point. The dog point length, Zs, is a minimum length for the dog point cylinder. The length of the dog point cylinder shall be measured from the point on the lead thread where the lead thread approximates 0.20x the thread pitch in height (measured from the thread root) to the point on the oylinder where the end radius is tangent. The diameter of the dog point cylinder, D,, shall be larger than D; minimum when measured at the tangent point. Dog point cylinder diameter D; shall be held for entire dog point length Zs with no taper allowed. 3.1.4 Radius Point. The radius point length, Zs, is a minimum length for the point beyond the dog point. The radius of this point, R, is a reference dimension only, and its shape may not be a true radius. The end of the point shall be reasonably square with the thread axis, and the edge may be irregular. The tip diameter, Dy, is a maximum for the radius point. 3.1.5 Point Length. The overall point length, Zs, is a maximum length. It represents the sum of the dog point length and the radius point length. 3.1.6 Minimum Full Thread Length. The minimum full thread length, Lf, is measured from the bearing surface or datum surface to a point where the last full thread is equal to the major diameter minimum tolerance limit. The minimum full thread can be derived by calculation or specified depencing on the fastener requirements, 3.1.7 Maximum Overall Length. The maximum overall (built-in) length, Mmax, is the sum of the maximum nominal length (maximum) and the maximum overall point length (Zs maximum). It is the maximum distance ‘rom the bearing surface to the end of the fastener, (Mmax). Figure 1: Dimension Illustration for Type A t roma euros)! y Lo! 5 FOR 80) Mmax Note: AEF = Relerencs, Table 1: Dimensions for Type A Thread ma | ms | Mo | me | mio | Miz) mia | mie | mie | M20 D, maximum] 3.170 | 4.030] 4.800] 6.540 | 8.230] 9.950] 11.720] 13.720] 15.172 |17.172 minimum | 3.993 | 3.954| 4.724] 6.447 | 8.143) 9.880| 11.604] 13.609 45.957, 17.057 reterence| 12 | 15 | 18 | 23 | 28] 33 | 41 | 47) 52) 60 reterence| 15 | 18 | 23 | 28 | 34 | 40| 45 | 45 | 56] 56 Z___minimum | 120 | 130 150] 210 | 260] 315 | 368 | 410] 440] 465 Z__maximum| 240 | 250| 285] 3.90 | 465| 565 | 643 | 7.10] 850] 8.80 Zs___minimum | 050 | aso | 075] 4.00 | 125] 150] 1.75| 200] 290] 321 Dy __maximum| 270 | 240 | 400] 550 | 680| 820| 960 | 10.90 | 1220 | 1330 R U {© Copyright 2019 Genera Motors Company lights Reserved April 2019 Page 2 of 5GM WORLDWIDE ENGINEERING STANDARDS GMW3362 3.2 Lnom Tolerance Limit Calculation Examples For Type A 3.2.1 It the design starts with a required minimum full thread (LA). Required full thread 47.1 mm for a M8 diameter fastener. Using equations and dimensions from Figure 1 and Table 1 Lf+T+U = Lnom, 47.1 + 0.15 + 2.8 = 50.05 = Lnom It was assumed the Tolerance (T) for Lnom is + 0.18, however, Lnom calculation using 0.15 > 50 Since Lnom is > 50, the tolerance is + 0.25 Recalculate as follows: U+T+U=Lnom, 47.1 +0.25 + 2.8 = 60.16 = Lnom Lnom + T = 50.15 + 0.25 = 50.04, Lnom - T = $0.15 - 0.25 = 49.90 Mmax = Lnom + T + Zs, 50.15 + 0.25 + 9.90 = 54.30 3.2.2 Requited maximum fastener overall length (Mmax). ‘The maximum overall MB fastener lenath for blind hole application is 50 mm. Using equations and dimensions from Figure 1 and Table 1 Mmax - T - Zs = Lnom, 60 - 0.15 - 3.90 = 45.95 (Lom) Tolerance for Lnom 50 is + 0.15, then, Loom + T = 45.95 + 0.15 = 48.10, Lnom - T = 45.95 - 0.15 = 45.80 Lt =Lnom - T- U, 45.95 - 0.15-2.8 = 43.00 Figure 2: Dimension Illustration for Type B Table 2: Dimensions for Type B er [seni ee os Pe reference ‘50 © Copyright 2019 General Motors Campary All Fights Reserved April 2019 Page 3 of 5GM WORLDWIDE ENGINEERING STANDARDS GMW3362 Figure 3: Dimension Illustration for Type C + rm Table 3: Dimensions for Type C Thread [ms MG Ms mio | mz | mia | m6 Driver Size -_|_F4 ES E7 EB Et E12 Ei4 u reference | 2.16 2.50 335 | 4.45 4.05 5.30 5.64 4 Validation 4.4 Inspection and Rejection. Samples of components or materials released to a GM general specification shall be tested for conformity with the requirements of this general specification and approved via Production Part Approval Process (PPAP) approval under Supplier Quality ‘Approval requires the supplier to provide evidence that: GM's requirements have been understood. The part supplied meets those requirements. The process (including sub-suppliers) is capable of producing conforming parts/product. The production control plan and quality management system will prevent non-conforming parts/product from reaching GM or compromising the safety and reliability of finished vehicles. ‘A new approval must be received for any changes, €.g., properties, manufacturing process, location of manufacture, etc. If not otherwise agreed, all testing and documentation normally required for initial release must be completed. Itis the responsibilty 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 approval. 5 Provisions for Shipping Not applicable. GO Screw Ring Gauge: A GO screw ring gauge checks the virtual size of the external thread (gauging the virtual pitch diameter); i.e., it checks the maximum material limit of the pitch diameter, taking into account deviations of form and pitch diameter (virtual pitch diamoter) of the workpiace. In addition, this gauge checks whether the length of the straight flank is adequate: ie. that the rounding at the root of the profile of the workpiece © Gopyrght 2019 General Motors Gampary All Fights Reserved April 2019 Page 4 of 5GM WORLDWIDE ENGINEERING STANDARDS GMW3362 thread does not encroach too far upon the flank of the thread. The major diameter of the external thread is not checked by this gauge. 6.2 Acronyms, Abbreviations, and Symbols. IMDS —_ international Material Data System Lnom Nominal Length mm Millimeter(s) Mmax Maximum Overall Length PPAP Production Part Approval Process REF Reference SSLT —_ Subsystem Leadership Team 7 Additional Paragraphs 7.1. All materials supplied to this standard must comply with GMW3059, Restricted and Reportable Substances, including the requirement to submit a full material composition disclosure to GM via the International Material Data System (IMDS). 7.2 Legal Regulations. Ali materials must satisty applicable laws, rules, regulations and recommendations valid in the country of usage. 8 Coding System This standard shall be referenced in other documents, drawings, etc., as follows GMws362 Example: GMW3362 Type A IF no type is referenced, the default is Type A 9 Release and Revisions This standard was originated in October 1999. It was first approved in February 2000. It was first published in June 2000. Issue | Publication Date Description (Organization) 1 JUN 2000 _| Initial publication. a JUN 2001 _| Editorial Revision. (GMNA) 3 MAY 2005 _| Reformatted, 3.1 added, Table 1. (Fasteners Group) 4 MAY 2008 _| Revise minimum Dx dimensions in Table 1. (Global Fastening SSLT) 5 MAR 2013 _| Five year refresh of standard. No technical changes - updated to 2013 template. (Global Fastening Engineering) 6 JUL2015 | Added provisions for points with an external driver end point. (Global Fastening Engineering) MAY 2017 _| Provision added for double end studs. (Global Fastening Engineering) 8 ‘APR 2019 | Added M4, Mi8 and M20 dimensions to Table 1. Removed remark related to calculation method in 1.3. Harmonize dimensional symbols in Section 3 and Figure 1. Revise 3.1.1 to clarify nominal thread length. Revised 3.1.6 to clarify the measurement of minimum full thread length (Lf). Revised 3.2 calculation ‘example match 3.1.1. Removed Initial Source Approval text in 4.4. (Global Fastening Engineering) {© Copyright 2019 General Motors Company All Rights Reserved April 2019 Page 5 of 5