1、BSI BS*Lb 51 162667 003362b O = BRITISH STANDARD SPECIFICATION UNIFIED BLACK HEXAGON BOLTS, SCREWS, NUTS (UNC at the same time, the bolt and nut committees of the American standardsbodies were preparing a revisionof the American Standard which represented a considerable simplification of previous pr
2、actice. 5 - BSI BS*ir2769 51 Lb24bb9 0033b3L 4 B.S. 1769 : 1951 Finally, at a conference held at the British Standards Institution, London, in April, 1951, attended by delegates from the United Kingdom, the United States and Canada, agreement was reached on the basic dimensions, for the normal and h
3、eavy series and overall limits were established with the provision that individual countries might, if they so desired, apply smaller tolerances within those limits. The Heavy Series bolts, screws and nuts to which this standard relates have hexagon sizes which are larger in proportion to the nomina
4、l diameter of thread than those in the Normal Series. The tolerances are comparatively wide, as is usual in the case of black bolts and nuts, but it is recognized that bolts and nuts of these dimensions may be required with a higher grade of finish for certain applications, and requirements are acco
5、rdingly included in respect of bolts faced under the head and machined on the shank and machined nuts. Normal Series bolts, screws and nuts from W in. to 1 in. inclusive are dealt with in a companion standzrd B.S. 1768, Unified Precision bolts, screws and nuts-Normal Series and are made to closer to
6、lerances in a variety of steels selected to provide a choice of closely controlled mechanical properties in the finished bolts and nuts. NOTE. The requirements for washers in this standard have been superseded by the publication of B.S. 3410. Metal washers for general engineering purposes, to which
7、reference should now be made. October. 1961 SPECWICATION SCOPE 1. This British Standard relates to the Heavy Series of Unified black hexagon bolts, screws and nuts having Unified screw threads in a range of nominal sizes from $4 in. to 2 in, inclusive. NOTE. It is considered that the range of nomina
8、l sizes included in this standard is adequate for most of the applications for which this series is likely to be employed, but for the convenience of users requiring larger sizes, the formulae from which the proportions for bolt heads and nuts are derived are given in Appendix A. 6 B.S. 1769 : 1951
9、2. The steel used for the manufacture of bolts, screws and nuts shall be such that the products possess mechanical properties as follows: Minimum tensile strength Minimum elongation As ontentled Jan. 1975 26 tonf/in2 or 28 tonf/in2 17%* 15%t In each case the minimum elongation is based on a gauge le
10、ngth of 5.65 I cross sectional area. In the case of hot forged bolts made to either of the above mechanical property groups the steel used shall not contain more than 0.06 percent each of sulphur and phosphorus. The choice of material to provide either of the mechanical property groups referred to a
11、bove will normally be at the option of the manufacturer, except where the purchaser specifically states which of the two he requires. Where the bolts, screws or nuts are required with mechanical properties different from those above the purchaser should specify the properties required in the enquiry
12、 or order. *Corresponding value for 4 x 16 = 20Pi tcorresponding value for 4 x d = I7 : “ISH 3. Unified black hexagon bolts, screws, nuts and washers shall be neatly and cleanly made. 4. The dimensions and tolerances of Unified black hexagon bolts, screws, and nuts, Heavy Series, shall be in accorda
13、nce with Tables I to 3 inclusive, and Clauses 5 to I I. DIMENSIONS LENGTH OF BOLTS AND SCREWS S. o. The nominal length of the bolts and screws shall be the distance from the underside of the head to the further end of the shank, the length of the machined point, if any, being regarded as part of the
14、 nominal length. b. The permissible tolerance on the nominal length shall be as follows :- Nominal Diameter Tolerance length on length 7 BSI BS*lJ7b7 51 W lb24bb 0033b33 8 W i B.S. 1769 : 1951 ENDS OP BOLTS AND SCREWS 6. The ends of bolts and screws may, at the option of the manufacturer, be finishe
15、d with either a flat chamfer or a radius approximately equal to 1% times the nominal diameter of shank, When bolts and screws are made with rolled threads the lead formed at the end of the bolt or screw by the thread rolling operation may be regarded as providing the necessary chamfer to the end, no
16、 other machining operation being necessary. SCREW THREADS 7. a. General. For bolts and screws as forged or faced under the head, and Asoleted for nuts as forged, the screw threads shall be Unified Coarse (UNC) Jon., 1960 in accordance with B.S. 1580, Unified screw threads, as specified by the purcha
17、ser. For bolts and screws faced under the head and machined on the shank and for machined nuts the screw threads shall be Unified Coarse (UNC), Unified Fine (UNF) in accordance with B.S. 1580, Unified screw threads , as specified by the purchaser. b. Bolls and screws, The screw threads may be either
18、 cut or rolled, at the option of the manufacturer, and shall conform fo the limits and tolerances for Class 2A specified in B.S. 1580, Unified screw threads. c. Nuts. The screw threads shall conform to the limits and tolerances for Class 2B specified in B.S. 1580, Unified screw threads. I I LENGTH O
19、F THREAD 8. a. Bols. The length of thread on bolts shall be the distance from the ciid of the bolt (including any chamfer or radius) to the leading face of a nut which has been screwed as far as possible on to the bolt by hand and shall be in accordance with the following dimensions :- Length of bol
20、t IJp to and including 6 in. Above 6 in. Length of thread 2D + W in. 2D + 1/2 in. Bolts that are too short for minimum thread length shall be threaded as screws. b. Screws. Screws shall be threaded to permit of a nut being screwed by hand to within a distance from the underside of the head equal to
21、twice the pitch. c. The permissible tolerance on the length of thread for bolts of all lengths shall not exceed plus in. or 2% threads, whichever is the greater. B.S. 1769 : 1951 CH AMPERMG a. Bolts and screws. Bolt heads and screw heads shall have a chamfer of approximately 30“ on their upper faces
22、. The lower or bearing face shall be machined only if specified on the order. b. Ordinary nuts. Ordinary nuts shall have a chamfer of approximately 30“ on one face and nuts up to and including 1 W in. nominal size may, at the option of the manufacturer, be similarly chamfered on both faces. The bear
23、ing face of the nuts shall be machined only if specified on the order. c. Lock nuts. Lock nuts shall have a chamfer of approximately 30“ on one or both faces, at the option of the manufacturer. Both faces of the nuts-shall be machined only if specified on the order. d. Slotted nuls. Slotted nuts sha
24、ll have a chamfer of approximately 30“ on their upper faces, and nuts up to and including 1% in. nominal size may, at the option of the manufacturer, be similarly chamfered on both faces. The bearing faces of the nuts shall be machined only if specified on the order. NOTE. The option referred to in
25、sub-clauses b, c and d above shall apply unless the purchaser in his enquiry and order specifically states that he requires the nuts to be- full bearing or c double-chamfered , Attention is drawn fo the fact that these alternative methods of finishing the lower face of nuts are associated both with
26、the nominal size and the particular method of . manufacture. A request by the purchaser for a specific type of finish limits the manufacturing processes available, and it is therefore recommended that the purchaser avoids making a request for a specific type of finish unless circumstances fully just
27、ify it. MACHINED NUTSSQUARENESS OF TIIREAD TO FACE . 10. When the bearing face of the nut is machined the axis of the thread of the nut shall be square to the face of the nut within the tolerances given below. The nut shall be screwed by hand on to a gauge having a truncated taper thread until the t
28、hread of the nut is tight on the thread of the gauge. A sleeve sliding on a parallel extension of the gauge, and which has a face of diameter equal to the minimum distance across flats of the nut and exactly at 90“ to the axis of the gauge shall be brought into contact with the leading face of the n
29、ut. With the sleeve in this position it shall not be possible for a feeler gauge of thickness equal to the squareness toler- ance to enter anywhere between the leading face of the nut and the face of the sleeve. (See Fig. 8.) 9 B.S. 1769 : 1951 Tolerance on squareness of face of nuts, Nomlnal diamet
30、er in. Squareness tolerance in. 0.015 0,016 0.019 0.023 0.023 0.027 0.027 0.030 0.030 0.030 0.035 DIAMETER OF SHANK OF BOLTS 11. a. The maximum diameter of the unthreaded portion of the shank of bolts shall be as follows :- Nominal diameter in. ,i% 1% 1% 2 1% fiaximum diameter in. 0.530 0.675 0.800
31、0,938 1.063 1.188 1.313 1.469 1.594 1.844 2.094 10 y- BSI BS*Lb7 51 W LbZLibb 0033636 3 W 0.500 o 0.625 O 0.750 O 0.875 O 1.OOo o 1.125 o 1.250 o 1.375 O 1.500 O 1.750 O 2000 o B.S. 1769 : 1951 0.494 O 0.619 O 0.744 O 0.869 o 0.994 o 1.117 O 1.242 O 1.367 O 1.492 O 1.742 O 1.990 o The shank diameter
32、 shaU be checked by means of a plain ring gauge having a maximum thickness equal to the nominal diameter of the bolt, a minimum fillet radius in the bore equal to the maximum radius under the bolt head and an internal diameter equal to the maximum shank diameter as specified above. The bolt shall en
33、ter the ring gauge up to the head. b. The unthreaded shank on bolts shall be machined only if stated by the purchaser in his order. When the shank is machined the following limits shall apply :- Nominal riLe Dinmeter of shank in. I in. 12. Bolts shall be identified as Unified by the incorporation of
34、 a circular recess in the upper surface of the head. Full details are given in Appendix B. NOTE 1. The dimensions given in Appendix B are for the guidance of the manu- facturer and shall not be regarded as part of the requirements of the standard. NOTE 2. The identification of Unified bolts by the m
35、ethbd. specified above is necwsary to cover the transition period during which this standard is becoming estab- lished; but at some future date, to be agreed later, marking will be discontinued. NOTE 3. No provision is made in this standard for the marking of nuts. When an As ad identification featu
36、re is considered desirable by the manufacturer or user, marking May should take the form of an indented groove. Details will be found in Appendix G of B.S. 1768, Unified Precision Hexagon bolts, screws and nuts (UNC and UNF threads) normal series. iied 1957 11 - 0033b37 5 B.S. 1769 : 1951 kW+ t 5 o,
37、 C 0) i 5 mK JO I Q II 1; 12 ,- - ES1 BS*27b 52 I Lb24bb 0033638 7 I 6.S. 1769 : 1951 omom omom O0 o 13 B.S. 1769 : 1951 14 B.S. 1769 : 1951 d E 4 _ td d E E E P z P - .N 15 BSI BS*17L 51 1b24bb 0033b41 7 in. 0.875 O 1,0625 1.2500 1.437 5 1.625 O 1.812 5 2.0000 2.187 5 2.3750 2.7500 3-1250 B.S. 1769
38、 : 1951 in, in, 0.855 O 1.01 1,0375 1.23 1,2250 1-44 1.407 5 1.66 1.5950 1-88 1.7825 2-09 1,9550 2.31 2.1425 2.53 2.3300 2.74 26900 3.18 3.0650 3.61 TABLE 3. UNlFIED HEXAGON SLOTTED NUTS-HEAVY SERIES (BEARING FACE MACHINED) (Third angle projection) Mt 4- # 3 O“ IL Fig. 9. Hexagon slotted nut, full b
39、earing Alternative types of hexagon slotted nuts. See Clause 9d and Note. Fig. 10. Double chamfered As alrere( - 1 - Nomin; D BiZC in. 1% 1% 2 nrcli, 1955 and Januarv. 1960 I 213 No. of threads per inch - UN -I 13 11 10 9 8 7 7 6 6 5 4% - - UNI - 20 18 16 14 12 12 12 12 12 - - - 41s16 Width cornera
40、-4 - *To be dispensed with wherever possible. Thickness G Max. _ in. 0.504 0.631 0.758 0.885 1,012 1.139 1.251 1d78 1.505 1.759 2,013 - - Min. _ in. 0,464 0.587 0.710 0,833 0.956 1.079 1.187 1,310 1.433 1.679 1,925 - Slot 16 BSI BS*1769 51 H 1b24bb7 00336112 9 B.S. 1769 : 1951 TABLE 4. PLAIN WASHERS
41、 Deleted bji Atiicridtiient No. 4, October., 1961 17 - BSI BS*17b 51 W Lb24hb 0033bY3 O - Tolerance plus or minus B.S. 1769 : 1951 ,APPENDIX A NOTE. The basic dimensions given in this standard are in accordance with those for the equivalent bolts and nuts in the American Standard, but in certain ins
42、tances smaller tolerances have been applied. Theproportions for bolt and screw heads and nuts in intermediate sizes and sizes larger than 2 in. should be derived from the formulae extracted from the American Standard and given in the following table. Tolerances should not exceed those derived from t
43、he formulae. Width SICTO91 corners (max.) A P OlllCI width Jmi. 19; I Height of herd Width across Rats I As for bolts. Ser above 0.016D +0.012 0.016D +Oe012 0.016D+0.012 0.016D+0.012 Ai for bolu. Sec above 3*016D+0-012 3.016D +0*012 3.016D +Ou012 3016D+O*012 l.016D +0*012 I 1.154 7 X Maximum width a
44、cross flats Bolt and screw hcads BCTOSS Tolerance tornen plus or minus (rnax.) _ in. in. 0.016D+O.012 1.154 7 x 0.016D +0*012 Maximum 0.016DS.0.012 width across flats Tolerance Nominal size D Height of head ?4 to % 1 to 1% 2 to 3 Facd I Width across Bah Iaickness t- Nominal Basic* Nuts I Tolerance m
45、inus Iliickness Nominal size D in. 0.050D 0*050D io, D D-464 D-%2 D-964 D-%6 in. 1 in. in. 134D i-% 1%D +% Orinary As forged Faced, plain and slotted Lock 0.050D 0.050D % toi% 1% to 2% w toi% 1% to2 2% 2% to4 234 to 3 3% to4 * The usc of bolts having nominal diameters to an odd ?46 in. is deprecated
46、, but in cas- where it ir unavoidable the above formula should be applied and the dimensions across flats adjusted to the nearest ?4e in. above. - 18 B.S. 1769 : 1951 APPENDIX B DETAILS OF IDENTIFICATION MARKING FOR UNIFIED HEXAGON BOLTS (see Clause 12) NOTE. All dimensions given are for the guidanc
47、e of the manufacturer and shall not be regarded as part of the requirements of the Standard. 1 Nomionl size D in. ?4 96 w 76 1 1% 1% 1% 1% 1% 2 U Fig. 12. Recessed bolt head 2 5 Recess Diameter A Mia To be dispensed with wherever possible. 19 Dcptb B Mas. in. 0*020 0.025 0.025 0.025 0.025 0*030 0.030 0.030 0-030 0.030 0030 Mio. in. 0.010 0.015 0.015 0-015 0.015 0.020 0020 0.020 0.020 0.020 O.oz0 r c
