1、UDC 621.882.15472.3: 621.882.211 :621.882.31 DEUTSCHE NORM May 199l Diameters of counterbores (holes) for hexagon bolts and nuts DIN 974 Part 2 Senkdurchmesser fr Sechskantschrauben und Sechskantmuttern; KonstruktionsmaBe This standard, together with DIN 974 Part 1, May 1991 edition, supersedes DIN
2、974, March 1972 edition. In keeping with current practice in standards published by the International Organization for Standardization (ISO), a comma has been used throughout as the decimal marker. This standard should be used in conjunction with DIN 74 Part 3, May 1991 edition, valid until 30 April
3、 1996. Dimensions in mm 1 Scope and field of application This standard specifies diameters of counterbores (holes) for hexagon bolts and nuts, in components with clearance holes. 2 Counterbore diameters This standard specifies two series of diameters of counterbores as a function of the assembly too
4、l (series 1 and 2). the diam- eters specified applying irrespective of whether a washer is used or not. The diameters should also be used for shallow type counterbores (see figure 2) produced by machining to provide a circular bearing face. Where space is restricted, series 3 diameters may be used f
5、or shallow type counterbores, unless DIN 6796 or DIN 6908 washers are used and wrenching is not impeded. Since, in table 1, the counterbore diameters have been specified as a function of the width across flats of bolts or nuts, the standard is applicable to all types of hexagon bolts and nuts irresp
6、ective of whether these are standardized or not. For informa- tion, the associated medium series clearance hole diameters, as specified in IS0 273, have been given in table l. Figure 1. Counterbore Figure 2. Counterbore, shallow type Where there is the risk of the edge of the hole being damaged by t
7、he screw underhead fillet, the edge shall be chamfered. This, however, will increase the pressure on the head bearing face. Continued on page 2 to 4 Beuth Verlag GrnbH. Berlin. has the exclusive right of sale for German Standards (DIN-Normen) 07.92 DIN 974 Part 2 Engl. Price group 5 Sales No.0105 Pa
8、ge 2 DIN 974 Part 2 Table 1. Counterbore diameters Series 21) Series 32) Series 11) For shallow type counterbores (where space is For boltsnuts For boltshuts fastened using DIN 6599 DIN 896? using DIN 838, DIN 897, DIN 3112 or DIN 3124 DIN 3129 wrench wrench restricted) Width across flats, s Nominal
9、 thread diameter, d Counterbore diameter, dl H13 11 13 15 11 9 3 3,4 15 10 4 4.5 18 11 5 535 54 58 61 73 76 82 61 46 22 24 73 48 24 26 76 54 27 30 a2 61 30 33 89 69 33 36 93 73 36 39 89 98 107 112 118 125 98 76 39 42 107 82 42 45 112 89 45 48 125 98 48 52 132 107 52 56 140 112 56 62 132 140 145 150
10、160 170 145 118 60 160 125 64 160 132 68 170 132 72 180 140 76 1 80 1 50 80 Diameter of clearance hole as in IS0 273, medium series, dh 5,5 7 8 10 13 16 18 24 28 20 26 33 13 18 22 6 1 10 66 9 11 1 73) 18 193) 28 33 33 33 36 36 22 26 26 10 I :2 11 13,5 13,5 21 24 223) 36 36 40 43 43 46 30 30 33 14 I
11、:s 15,5 15,5 17,5 27 30 323) 43 46 54 50 54 61 36 40 46 18 1 22 20 22 24 34 36 41 46 50 55 60 65 70 75 80 85 90 95 1 O0 66 70 74 105 110 115 78 82 86 1) Irrespective of the allocation of assembly tools made to series 1 and 2, it is quite possible that tools specified for series 2 2) Too large a coun
12、terbore depth involves the risk of wrenching being impeded. Series 3 counterbores are not suitable for 3) These widths across flats are not covered in IS0 272. counterbores can also be used for series 1 counterbores. use with conical spring washers. 3 Definition of a counterbore A counterbore is def
13、ined by its diameter, dl, and its depth, t (cf. figure 1). This standard does not specify the depth, which is to be chosen as a function of the particular application. It is, however, recommended that the required depth be determined as follows. For the screw head to be flush with the component surf
14、ace, the required depth is obtained as the sum of the maximum values of head height and washer height plus an allowance as specified in table 2. DIN 974 Part 2 Page 3 The counterbore depth on the nut side shall be specified with adequate allowance being made for the bolt end projection. Nominal thre
15、ad diameter, d Allowance From 3 to 6 Over 6up to20 Over 20 up to 27 Over 27 up to 80 Example: Determination of counterbore depth, t, for a DIN 933 - M 12 x 80 - 8.8 hexagon head screw used with a DIN 6796 - 12 - FSt conical spring washer: maximum head height: k, = 7,68 mm; maximum washer thickness:
16、h, = 3,06 mm; allowance: 0,6 mrn; t = km, i h, + allowance = 11,34 mm. The result is to be rounded as required. Where more than one washer is used (screw and washer assemblies), the maximum washer heights shall be added to obtain hmax In the case of shallow type counterbores, t need not be greater t
17、han required to produce by machining a circular bearing face at right angles to the clearance hole axis. 4 General tolerances Sizes (except d,), form and position are subject to the general tolerances indicated on the drawing. Where no such tolerances are specified, the general tolerances, accuracy
18、grade mB, as specified in DIN 7168, shall apply. Standards referred to DIN 659 DIN 838 DIN 896 DIN 897 DIN 933 DIN 3112 DIN 3124 DIN 3129 DIN 6796 DIN 6908 DIN 7168 IS0 272 : 1982 IS0 273 : 1979 Tubular single end tee socket wrenches Ring wrenches with double end, deep offset, with different widths
19、across flats; series A test torques Tee wrenches with double end; series A test torques Ring wrenches with double end, modified offset, with different widths across flats; series A test torques M 1,6 to M 52 hexagon head screws threaded up to the head; product grades A and B Single end tee wrenches
20、with socket Square drive socket wrenches for hexagon bolts, hand-operated Square drive socket wrenches for hexagon bolts, machine-operated Conical spring washers for bolthut assemblies Conical spring washers for screw and washer assemblies General tolerances for linear and angular dimensions and geo
21、metrical tolerances (not to be used for new designs) Fasteners: hexagon products, widths across flats Fasteners: clearance holes for bolts and screws Other relevant standards DIN 74 Part 2 DIN 74 Part 3 Counterbores (holes) for cheese head, pan head and hexagon socket head cap screws Counterbores (h
22、oles) for hexagon bolts and nuts Previous editions DIN 974: 06.68,03.72 Page 4 DIN 974 Part 2 Amendments The following amendments have been made to the March 1972 edition of DIN 974. a) The standard has been split up into Part 1 and Part 2. b) Counterbore diameter series have been specified as a fun
23、ction of assembly tool types. c) Tolerances on counterbore diameter have been specified. d) The number of counterbore diameters specified has been reduced by combining diameters of similar magnitude. e) A number of diameters for special screw types are no longer included. f) The surface roughness fo
24、r the counterbore has been specified. g) A method of determining the counterbore depth has been recommended. h) Counterbores are now subject to general tolerances. Explanatory notes Revision of DIN 74 Parts 2 and 3 was prompted by the fact that the specifications of Part 3 did not adequately cover t
25、he range of counterbore depths required in practice, mainly as a result of differences in washer height and the large number of possible washer combinations. It was deemed expendient in future to standardize only the diameters of counterbores and to leave it to the user to specify their depth. Howev
26、er, such specifications must be based on certain principles. As there was already a standard dealing with counterbore diameters, DIN 974, it was decided to revise it, dividing it into two Parts (one covering diameters of counterbores for cheese head, pan head and hexagon socket head cap screws (Part
27、 l), and the other, for hexagon screws and nuts (Part 2). Whereas previously, thread nominal diameters were correlated with counter- bore diameters, series of counterbore diameters have now been specified and assigned to thread nominal diameters. When establishing the counterbore diameters for the i
28、ndividual series, care was taken to keep the number of possible diameters within reasonable limits. To facilitate identification of counterbores in existing documentation based on DIN 74 Parts 2 and 3, these standards, as now revised, are to remain valid for the transitional period stated. For new d
29、esigns it is recommended that specifications for counterbores be based on DIN 974 Part 1. It should be noted that counterbores as specified in DIN 974 are suitable for IS0 screws and nuts, which does not apply in all cases for counterbores as specified in DIN 74. International Patent Classification F 16 B 5/02
