1、FORD WORLDWIDE FASTENER STANDARDDate: 1996-10-01Engineering Standards & 1 of 9 Printed copies are uncontrolled .Systems Engineering (ESSE)WD 900General Specifications for Spaced Thread Tapping Screws1. SCOPE.This standard specifies the general and dimensional requirements for spaced thread tapping s
2、crews withvarious head forms.2. REFERENCES.ISO 1478 - Tapping Screws ThreadWD 950 - Material and Performance requirements for Carbon Steel Tapping Screws3. GENERAL REQUIREMENTS.3.1 DIMENSIONS AND TOLERANCES.The dimensions and tolerances of Pan Head, Round Washer Head, Raised Countersunk Head, FlatCo
3、untersunk Head, Hexagon Head and Flanged Hexagon Head Spaced Thread Tapping screwsmust be in accordance with Tables 1 thru 6, Figures 1 thru 5 included in Clauses 2 thru 7, andAppendices A, B and C as appropriate.3.2 SCREW THREADS.3.2.1 THREAD LENGTH.For types AB and B screws of nomina l lengths equ
4、al to 8 diameter or 38mm, whichever isshorter, the full form threads shall extend close to the head such that the specified minordiameter limits are maintained to within one pitch maximum from the underside of head.Screws of longer nominal lengths shall have a minimum length of full form thread equa
5、lto 6 diameters or 38mm, whichever is shorter.3.2.2 SCREW LENGTH.The length of the screw shall be measured parallel to the axis of the screw from the largestdiameter of the bearing surface of the head to the extreme point. The tolerance on lengthshall be as specified in Table 1 with minimum practica
6、l screw lengths as shown in Table1a.FORD WORLDWIDE FASTENER STANDARDDate: 1996-10-01Engineering Standards & 2 of 9 Printed copies are uncontrolled .Systems Engineering (ESSE)WD 900General Specifications for Spaced Thread Tapping ScrewsTable 1. Tolerance on lengthScrew Type Nominal Screw Length Toler
7、ance onLength mmAB Up to 25mm inclusive +/- 0.8Over 25mm +/- 1.3Up to 20mm inclusive +/- 0.8B, D and TR Over 20mm to 40mm inclusive +/- 1.3Over 40mm +/- 1.5Table 1a. Minimum practical screw lengthsDimensions in mmNominal 90 o Heads Countersunk HeadsSize TypeABType B TypeABType BST 2.9 4.8 3.6 5.5 4.
8、8ST 3.5 5.5 4.4 6.7 6.3ST 4.2 7.1 4.8 8.3 6.3ST 4.8 8.3 5.9 9.5 7.9ST 5.5 9.5 7.1 10.3 9.5ST 6.3 10.3 7.1 11.9 9.53.2.3 THREAD FORM. Thread form shall be as specified in ISO 1478.3.3 RECESSES.The dimensions and tolerances of recesses in Pan Head, Round Washer Head, Raised CountersunkHead and Flat Co
9、untersunk Tapping Screws shall be in accordance with Appendix B.3.4 GAUGING.3.4.1 COUNTERSUN K HEADS. For referee purposes the dimensions k and d k are satisfied ifthe heads meet the gauging requirements specified in Appendix C.3.4.2 PENETRATION GAUGE. The method of penetration gauging, the gauge an
10、d the gaugepoint are defined in Appendix B.4. GENERAL REQUIREMENTS - PAN HEAD.4.1 HEAD DIMENSIONS. Head dimensions shall be as specified in Table 2.NOTE: The truncation of the rounded surface due to the cross recess is not considered part ofthe head height.FORD WORLDWIDE FASTENER STANDARDDate: 1996-
11、10-01Engineering Standards & 3 of 9 Printed copies are uncontrolled .Systems Engineering (ESSE)WD 900General Specifications for Spaced Thread Tapping Screws4.2 CROSS RECESS DEPTH.The depth of cross recess (penetration gauging) shall be measured parallel to the axis of the screwshank and shall be in
12、accordance with values specified in Appendix B.Figure 1. Pan head screwsTable 2. Principle head dimensionsDimensions in mmNominal Size ST2.9 ST3.5 ST4.2 ST4.8 ST6.3Pitch 1.1 1.3 1.4 1.6 1.8d k max 5.6 7 8 9.5 12min 5.3 6.6 7.6 9.1 11.5k max 2.4 2.6 3.1 3.7 4.6min 2.2 2.3 2.8 3.4 4.3a max 1.1 1.3 1.4
13、 1.6 1.8d a max 3.5 4.1 5 5.6 7.3f ref 5 6 6.5 8 10Driver Size 1 2 2 2 3r min 0.1 0.1 0.2 0.2 0.255. GENERAL REQUIREMENTS - COUNTERSUNK HEADS.5.1 HEAD DIMENSIONS.5.1.1 OVAL HEAD. See Table 4.1.5.1.2 FLAT HEAD. See Table 4.2NOTE: On heads having rounded top surfaces, the truncation of the rounded sur
14、facedue to the recess is not considered part of the head height.FORD WORLDWIDE FASTENER STANDARDDate: 1996-10-01Engineering Standards & 4 of 9 Printed copies are uncontrolled .Systems Engineering (ESSE)WD 900General Specifications for Spaced Thread Tapping ScrewsFigure 2. Raised Countersunk (Oval) H
15、ead ScrewsTable 4.1. Principal oval head dimensionsDimensions in mmNominal Size ST3.5 ST4.2Theoretical max 8.2 9.4d k Actual max 7.3 8.4min 6.9 8k max 2.4 2.6a max 1.3 1.4f ref 0.8 1r max 1.4 1.6t f ref 8.5 9.5Driver Size 2 2Figure 3. Flat Countersunk head screwsTable 4.2. Principal flat head dimens
16、ionsDimensions in mmNominal Size ST3.5 ST4.2 ST4.8Theoretical max 8.2 9.4 10.4d k Actual max 7.3 8.4 9.3k max 2.35 2.6 2.8a max 1.3 1.4 1.6r max 1.4 1.6 2Driver Size 2 2 2FORD WORLDWIDE FASTENER STANDARDDate: 1996-10-01Engineering Standards & 5 of 9 Printed copies are uncontrolled .Systems Engineeri
17、ng (ESSE)WD 900General Specifications for Spaced Thread Tapping Screws5.2 SIDE HEIGHT.The side height of flat and raised countersunk heads (k) is a reference dimension measured parallelto the axis of the screw from the largest theoretical diameter of the bearing surface of the head tothe point of in
18、tersection of the bearing surface of the head and basic major diameter of screw forfull headed screws, and from the largest theoretical diameter of the bearing surface of the head tothe commencement of the truncation for truncated head screws.5.3 CROSS RECESS DEPTH.The depth of cross recess (penetra
19、tion gauging) shall be measured parallel to the axis of the screwshank and shall be in accordance with the value specified in Appendix B.6. GENERAL REQUIREMENTS - HEXAGON HEAD.6.1 HEAD DIMENSIONS.Across corners, across flats and overall height shall be as specified in Table 5.6.2 FILLET RADIUS.The r
20、adius of the fillet under the bearing surface of the head shall be no greater than 15% of thebasic screw diameter.6.3 EDGE ROUNDING.A slight rounding of all edges and corners of the hexagon head is permissible provided thediameter of the bearing surface is not less than 90% of the minimum “across fl
21、ats“ dimension.FORD WORLDWIDE FASTENER STANDARDDate: 1996-10-01Engineering Standards & 6 of 9 Printed copies are uncontrolled .Systems Engineering (ESSE)WD 900General Specifications for Spaced Thread Tapping Screws6.4 INDENTATION AND HEAD MARKING.The optional indentation in head shall not impair fun
22、ction of part. Shape is optional with themanufacturer.Figure 4. Hexagon head screwsNOTES: For EAO procurement heads mus t be marked CH as shown in Figure 4.For NAAO procurement and assembly:Heads must be marked to identify manufacturer and metric. Metric identification shall consist ofMET or the num
23、eral 2, at the manufacturers option, located on the top surface of the head andraised 0.2mm to 0.4mm, or indented. The minimum height of the markings shall be 0.25 times themaximum width across flats.Table 5. Principal head dimensionsDimensions in mmNominal Size ST2.2 ST2.9 ST3.5 ST4.2 ST4.8 ST6.3s
24、max 3.2 5 5.5 7 8 10min 3.02 4.82 5.32 6.78 7.78 9.78e min 3.36 5.36 5.92 7.55 8.66 10.89k max 1.27 1.52 2.36 2.79 3.05 4.83min 1.02 1.24 2.03 2.44 2.67 4.377. GENERAL REQUIREMENTS - HEXAGON FLANGE HEAD7.1 HEAD DIMENSIONS.Dimensions shall be as specified in Table 6.FORD WORLDWIDE FASTENER STANDARDDa
25、te: 1996-10-01Engineering Standards & 7 of 9 Printed copies are uncontrolled .Systems Engineering (ESSE)WD 900General Specifications for Spaced Thread Tapping Screws7.2 INDENTATION AND HEAD MARKING.The optional indentation in head shall not impair function of part. Shape is optional with themanufact
26、urer.Figure 5. Flanged hexagon screwsNOTES: For EAO procurement heads must be marked CH as shown below.For NAAO procurement and assembly:Heads must be marked to identify manufacturer and metric. Metric identification shall consist ofMET or the numeral 2, at the manufacturers option, located on the t
27、op surface of the head andraised 0.2mm to 0.4mm, or indented. The minimum height of the markings shall be 0.25 times themaximum width across flats.Table 5. Principal head dimensionsDimensions in mmNominal s e d c c k k 1 r r 1 d aSize Max.Min. Min. Max.Min. Min. Max.Min. Max.Min. Max.ST2.9 4 3.84 4.
28、27 5.7 5.2 0.4 3 2.1 0.2 0.1 3.5ST3.5 5 4.85 5.4 7.5 7 0.45 3.6 2.3 0.2 0.1 4.1ST4.2 5.5 5.32 6 8.2 7.5 0.55 4 2.8 0.2 0.2 5ST4.8 7 6.78 7.6 9.8 9 0.6 5.2 3.3 0.3 0.2 5.6ST6.3 8 7.78 8.66 12.2 11.2 0.95 6.2 4.2 0.4 0.3 7.37.3 GAUGE MEASUREMENT REQUIREMENTS.7.3.1 GAUGING OF THE HEAD OF FLANGED HEXAGO
29、N HEAD PRODUCTS. The headshall be gauged using two ring gauges, A and B, to demonstrate the coincidentalacceptability of hexagon height, wrenching height, corner fill, width across corners andflange thickness at the junction with the hexagon portion.Gauge A shall be placed over the head as shown and
30、 the head then seated axially inGauge B. When Gauge A is in contact with the flange as shown below, the opposite facemust not contact Gauge B.Gauge dimensions are specified in Table 7.FORD WORLDWIDE FASTENER STANDARDDate: 1996-10-01Engineering Standards & 8 of 9 Printed copies are uncontrolled .Syst
31、ems Engineering (ESSE)WD 900General Specifications for Spaced Thread Tapping ScrewsFigure 6. Gauging of flanged hexagon headsTable 7.Dimensions in mmNominal Size ST2.9 ST3.5 ST4.2 ST4.8 ST6.3D + 0.00- 0.014.62 5.75 6.35 8.08 9.24C + 0.00- 0.011.89 2.04 2.52 2.97 3.78G + 0.00- 0.014.26 5.39 5.99 7.59
32、 8.65M Min. 2 2 3 3 3FORD WORLDWIDE FASTENER STANDARDDate: 1996-10-01Engineering Standards & 9 of 9 Printed copies are uncontrolled .Systems Engineering (ESSE)WD 900General Specifications for Spaced Thread Tapping Screws7.3.2 GAUGING OF THE HEAD OF PLAIN HEXAGON HEAD PRODUCTS. The head shallbe gauge
33、d using two plain ring gauges A and B to demonstrate the coincidentalacceptability of minimum wrenching height and corner fill. Products are to be gaugedafter plating. The orientation of the gauges is optional but in cases of dispute the methodshown in Figure 7 shall be the referee method.Gauge B sh
34、all be places on flat horizontal surface. The head shall be seated axially inGauge B as shown in Figure 7 gauge A shall be placed over the head as shown in Figure7. The gauges shall not touch.Figure 7. Gauging of the plain hexagon headsTable 8.Dimensions in mmNominal Size ST2.2 ST2.9 ST3.5 ST4.2 ST4.8 ST6.3D + 0.00- 0.013.71 4.62 5.75 6.35 8.08 9.24C + 0.00- 0.010.89 1.06 1.66 1.95 2.14 3.38G + 0.00- 0.013.35 4.26 5.39 5.99 7.59 8.65M Min. 2 2 2 3 3 3E Ref. 3 3.5 4 5 5.5 7
