1、(RED WORLDWIDE STANDARD WB 900 DATE: 1996 JULY General and Dimensional Requirements of Pan Head, Raised Countersunk Head and Flat Countersunk Head Machine Screws, and Machine Screw and Tooth Washer Assemblies 1. SCOPE. This standard specifies the general and dimensional requirements of pan head, rai
2、sed countersunk head and flat countersunk head machine screws and machine screw and machine screw and tooth lock washer assemblies with recess drive systems. Cross recess data is shown in Appendix A. Lobed recess data is shown in Appendix D. 2. REFERENCES. IS0 261 IS0 965 IS0 1502 IS0 4762 IS07721 W
3、A 900 WA 990 - IS0 General purpose metric screw threads - General plan. - IS0 General purpose metric screw threads - Tolerance. - IS0 General purpose metric screw threads - Gauging. - Hexagon socket head cap screws - Product grade A. - Countersunk head screws - Head conf&ration and gauging. - Dimens
4、ional requirements for hexagon and flanged hexagon bolts and screws, and hexagon screw and washer assemblies. - Surface discontinuities of bolts and screws. 3. GENERAL REQUIREMENTS. 3.1 DIMENSIONS AND TOLERANCES. The dimensions and tolerances of pan head, raised countersunk head and flat countersunk
5、 head machine screws, and machine screw and tooth lock washer assemblies shall be in accordance with Clauses 1 - 8, Tables 1 - 4 and Figures 1 - 4. 3.2 WASHERS. The dimensions, tolerances and materials requirements of the washer component of machine screw and tooth lock washer assemblies shall be in
6、 accordance with WF 900. The washer shall be free to rotate while disassembly from the screw is prevented. 3.3 RECESSES. The dimensions and tolerances of recesses in pan head, raised countersunk head and flat countersunk head machine screws, and machine screw and tooth lock washer assemblies shall b
7、e in accordance with the requirements in Appendix A. 3.4 PILOT POINTS. The dimensions, tolerances and form and position tolerances of pilot points shall be as specified in WA 900. 3.5 GAUGING. 35.1 COUNTERSUNK HEADS. For referee purposes the dimensions k and 4 are satisfied if the heads of countersu
8、nk screws meet the gauging requirements specified in Appendix B. 3.5.2 SCREW RING GAUGE. The screw rin, s Q oauge used in the determination of length of thread shall conform to the dimensions and tolerances defined in IS0 1502 appropriate to the specified thread and class of fit. The Ml thread shall
9、 commence immediately at the gauge face. 3.5.3 PENETRATION GAUGING. The method of penetration gauging, the gauge and the gauge point are defined in Appendix A. 3.6 PROTECTIVE FINISH. All dimensions and tolerances defmed in this specification apply prior to the application of the protective finish ex
10、cept where otherwise specified. PAGE 1 OF 7 WORLDWIDE STANDARD w-B900 DATE: 1996 JULY General and Dimensional Requirements of Pan Head, Raised Countersunk Head and Flat Countersunk Head Machine Screws, and Machine Screw and Tooth Washer Assemblies 4. LENGTH. 4.1 NORMAL LENGTH. The normal length of a
11、 machine screw or a machine screw and tooth lock washer assembly is the distance from the bearing face or, in the case of countersunk screws, the theoretical junction of the countersunk face and the top of the head, to the furthest end of the threaded portion including any chamfer or radius but excl
12、uding a special feature such as a dog point. The nominal length of a machine screw or machine screw and tooth lock washer assembly having a special feature such as a dog pain is the junction of the countersunk face and the top of the head, to the commencement of the special feature. 4.2 TOLERANCE OF
13、 LENGTH. The length of machine screws and machine screw and tooth lock washer assemblies shall be within the tolerance on nominal length specified in the table below. f/ Over 1 IOup to and including 18 1 +/-0.35 (1 1 Over 1 18 up to and including 30 1 +/- 0.42 11 Over 1 180 up to and including 250 1
14、 +/- 0.93 5. LENGTH OF THREAD AND THREAD RUN-OUT (REFEREE METHOD). 5.1 THREAD. In cases of dispute the thread length b shall be measured as the distance from the end of the screw to the leading face of a screw riug gauge (See Clause 3.52) which has been screwed as far as possrble onto the screw by h
15、and. 52 RUN-OUT. In cases of dispute dimensions a and x shall be measured using the ring gauge specified in Clause 3 52 screwed as far as possible onto the screw by hand. 6. DIAMETER OF SHANK (UNTHREADED PORTION). 6.1 SCREWS. The diameter of the unthreaded portion may be approximately equal to the p
16、itch diameter (i.e., the normal thread rolling diameter) appropriate to the size of the thread or, alternatively, equal to the major diameter as specified in IS0 965. 6.2 SCREW AND TOOTH LOCK WASHER ASSEMBLIES. The diameter of the unthreaded portion of screw and tooth lock washer assemblies shall be
17、 less than the major diameter of the screw thread by an amount sufficient to allow free rotation of the washer. PAGE 2 OF 7 ziiiim WORLDWIDE STANDARD WB 900 DATE: 1996 JULY General and Dimensional Requirements of Pan Head, Raised Countersunk Head and Flat Countersunk Head Machine Screws, and Machine
18、 Screw and Tooth Washer Assemblies 7. SCREW THREADS. 7.1 Prior to any surface treatment screw threads must conform to the dimensions and tolerances specified in IS0 261 and IS0 965 tolerance class 6g. 7.2 After electro or mechanical plating (when specified) screw threads may exceed the maximum dimen
19、sions for 6g, unless otherwise specified on the part drawing, but must not exceed the maximum dimensions for tolerance class 4h. 8. FORM AND POSITION TOLERANCES. 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 CONCENTRICITY OF SHANK TO THREAD. The concentricity of the shank (measured over dimension A - See Figure 4
20、 and Clause 8.7) shall be within the values specified in Table 4. CONCENTRICITY OF PAN HEAD TO SHANK OR THREAD. The concentricity of the recess to the shank or thread (measured over dimension A - See Figure 4 and Clause 8.7) shall be within the values specified in Table 4. CONCENTRICITY OF RECESS TO
21、 SHANK OR THREAD. The concentricity of the recess to the shank or thread (measured over dimension A - See Figure 4 and Clause 8.7) shall be within the values specified in Table 4. RUN-OUT OF COUNTERSUNK FACE TO SHANK OR TIIREAD. The run-out of the countersunk face of flat cotmtersunk and raised coun
22、tersunk heads to the shank or thread (measured over dimension A - See Figure 4 and Clause 8.7) shall be within the values specified in Table 4. STR4IGHTNESS. The straightness (measured over dimension L - See Figure 4.) shall be within the values specified in Table 4. SQUARENESS OF THE BEARING SURFAC
23、E OF PAN HEADS TO THE SHANK OR THREAD. The bearing surface (measured over a diameter of 0.8dJ shall be square to the shank or thread (measured over dimension A - See Figure 4 and Clause 8.7) within 1”. FORM AND POSITION TOLERANCES - METHOD OF MEASUREMENT. When the datum feature is the threaded porti
24、on, the datum diameter shall be the Pitch Diameter. Alternatively a GO Screw Ring Gauge to IS0 1502, tolerance class 6h with a 05d minimum thickness may be used. POSITION TOLERANCES FOR PILOT POINTS SHALL BE AS SPECIFIED IN WA 900 TABLE 10 AND FIGURE 10. 9. SURFACE ROUGHNESS. The surface roughness o
25、f the bearing face shall be evaluated in line with WA 990 Clause 2.5. PAGE3 OF7 iiliim WORLDWIDE STANDARD WBPOO DATE: 1996 JULY General and Dimensional Requirements of Pan Head, Raised Countersunk Head and Flat Countersunk Head Machine Screws, and Machine Screw and Tooth Washer Assemblies Figure 1.
26、-It- f - -II x b L k L PLAIN SHANK SCREWS Size Pitch Driver size b min. 4 max. 3.1 1 3.6 1 4.1 dk max. min. k max. min. r min. rf ref. X max. 4 ref. a) max. HEIGHT OF THE COMPRESSED WASHER = + tsEE WF 900) hl (SEEWFSOW lr INCOMPLETE l-l-READ Table 1. 2 PITCHES MAX. INCOMPLETE THREAD M2.5 M3 M3.5 M4
27、M5 M6 M8 Ml0 0.45 0.5 0.6 0.7 0.8 1 1.25 1.5 1 I 2 1 3 I 4 25 1 25 1 38 Dimensions in mm 1.96 7 226 1 2.46 38 1 38 1 38 1 38 1 38 0.2 1 0.2 1 0.25 1 0.4 1 0.4 1.4 1 1.k -T 2 T 2.5 r 3 1) a max for screw and washer assemblies shall be the free height (h,) of the washer plus 2 pitches. PAGE 4 OF 7 m 9
28、00=ll,b0 0054347 7T5 m !sB WORLDWIDE STANDARD WB 900 DATE: 1996 JUL,Y General and Dimensional Requirements of Pan Head, Raised Countersunk Head and Flat Countersunk Head Machine Screws, and Machine Screw and Tooth Washer Assemblies Figure 2. Raised countersunk screws r SCREWS WfTH PLAIN SHANK MSGHT
29、OF THE COMPRESSED TOOTH LOCK WASHER = h2 (SEE WF 900) A Yw (SEE WF 900) Table 2. T = Theoretical. A = Actual 2 PITCHES MAX. INCOMPLETE THREAD Dimensions in mm Size PAGE 5 OF 7 aa!BB WORLDWIDE STANDARD WJ3900 DATE: 1996 JULY General and Dimensional Requirements of Pan Head, Raised Countersunk Head an
30、d Flat Countersunk Head Machine Screws, and Machine Screw and Tooth Washer Assemblies Figure 3. Flat countersunk screws P , -lt . - dJyp i * . I S-EWS w(Tn PLAIN SMNK NCOMPLEIE THREAD WEIGHT OF THE COMPRESSED l- TOOTH LOCX WASHER - h2 (SEE WF 9C01 PrrcNEs MAX. INCOMPLETE THREAD Table 3. T = Theoreti
31、cal. A = Actual Dimensions in mm PAGE 6 OF 7 !EB WORLDWIDE STANDARD WB 900 DATE: 1996 JULY General and Dimensional Requirements of Pan Head, Raised Countersunk Head and Flat Countersunk Head Machine Screws, and Machine Screw and Tooth Washer Assemblies Figure 4. Form and position tolerances TabIe 4.
32、 Tolerance for concentricity and straightness Dimensions in mm Nominal Thread Diameter d M2.5 M3 M3.5 M4 M5 M6 MS Ml0 Concentricity - Thread to shank 0.28 0.36 0.44 Concentricity - Head to shank or Thread for Pan Head Screws 0.36 0.44 0.54 0.66 Concentricity - Recess to shank or Thread 0.28 0.36 0.4
33、4 Run-out - Countersunk i bearing face to 0.28 Thread or shank 0.36 0.44 Straightness 0.002 L + 0.05 0.0025 L + 0.05 1) For machine screws which have a shank length (unthreaded portion) less than “d”, the full length of shank shall be the datum for concentricity measurements. 2) The datum length “A” shall not be partly shank and partly thread or incorporate the thread run-out. If necessary the datum feature shall be displaced at sufficient distance from the head to avoid the thread run-out. NOTE: The above dimensions represent Total Indicator Movement, PAGE 7 OF 7
