bolt length hsb
TRANSCRIPT
Specifying Bolt Length for High-Strength Bolts
CHARLES J. CARTER
INTRODUCTIONTwo tables that are useful in determining the proper boltlength for high-strength bolts are provided in the AISCManual of Steel Construction:1 Table 8-2, which includesconstants to be added to the grip and washer thickness(RCSC Specification Table C22 is the basis for theseconstants) and a table in Figure 8-3, which indicates theouter-ply thickness required to exclude the threads from thefaying surface of the connection. While it is a simpleoperation to select bolt lengths using these tables, therepetitive calculation becomes somewhat tedious and couldbe simplified.
In this paper, a design aid is presented for the selectionof high-strength bolt lengths for bearing (snug-tightenedand fully tensioned) and slip-critical connections. Nominalbolt lengths are tabulated based upon the grip for ¾-in.,7/8-in., 1-in., and 1 1/8-in. diameter ASTM A325 and A490bolts with zero, one, or two 5/32-in.-thick ASTM F436 flatwasher(s) and an ASTM A563 nut; bevelled washers arenot considered in this paper. Additionally, the outer-plythickness required when it is desired to exclude the threadsfrom the shear plane is tabulated. Example problems areincluded to illustrate use of the table. The following topicsare also briefly addressed in this paper: (1) tolerances onbolt length, nut thickness, and washer thickness; (2) threadrun-out, stick-through requirements, and risk of jammingthe nut; (3) washer requirements; and, (4) excluding threadsfrom the shear plane of the connection.
MINIMUM BOLT LENGTH
The minimum possible length of high strength bolts iscalculated by summing the nominal grip, the nominalthickness of washer(s), and the appropriate value fromTable C2 of the Specification for Structural Joints UsingASTM A325 or A490 Bolts.2 Values in RCSC SpecificationTable C2 provide for the nominal thickness of the heavyhex nut and the following tolerances: (1) the minustolerance on bolt length; (2) the plus tolerance on washerthickness; and (3) the plus tolerance on nut thickness. Byone order of magnitude, the tolerance on bolt length is themost significant; see Appendix. Taking the worst caseaccumulation of these three tolerances, Table 1 illustratesthat the values in RCSC Specification Table C2 are
Charles J. Carter is senior staff engineer, American Institute of SteelConstruction, Inc., Chicago, IL.
conservative for all bolts less than or equal to 6-in. long.For bolts longer than 6 inches, the values are conservativefor 1 1/8-in. diameter bolts and negligibly unconservative(within 3/64-in.) for ¾-in., 7/8-in., and 1-in. diameter boltsassuming. This is considered to be negligible because theworst-case accumulation of tolerances assumed is astatistical improbability. The nominal bolt length is thenselected as the next larger increment based on the minimumpossible length. As is general industry practice, for boltlengths less than 5 inches, a nominal length increment of¼-in. is used; otherwise, a nominal length increment of ½-in. is used.
In the installed condition, even if the nominal length isexactly equal to the minimum possible length, the end ofthe bolt will be at least flush with the end of the nut. Someproject specifications include a stick-through requirement(minimum protrusion of the bolt point beyond the nut).However, because the threaded length for any given boltdiameter is constant regardless of the bolt length, a stick-through requirement may require a longer bolt and therebyincreases the risk of jamming the nut on the thread run-out.Because a stick-through requirement does not improve theperformance of the bolt, its specification is discouraged.
In Table 2, bolt lengths L have been tabulated for ¾-in.,7/8-in., 1-in., and 1 1/8-in. diameter ASTM A325 and A490bolts with zero, one, or two 5/32-in.-thick ASTM F436washer(s). Because 8 inches is generally the maximumstock bolt length available except by special order,tabulated values for combinations requiring longer lengthshave been omitted. The tabulated values are valid forconventional high-strength bolts and alternative designfasteners, such as tension-control or twist-off bolts. Ifdirect tension indicator devices are to be used, the tabulatedvalues remain useful if the thickness of such devices isconsidered to be part of the grip.
In many cases when one washer is used, the minimumpossible bolt length exceeds a nominal length increment by1/32-in. For example, a ¾-in. diameter bolt with one 5/32-in.-thick washer and a 7/8-in. grip would require a length of
in.2132
5
8
732
1=++
where 1 inch is the value from RCSC Specification TableC2. In this and other such cases, the tabulated minimumbolt length has been rounded down to the shorter nominallength increment because 1/32-in. is negligible. In all othercases, the tabulated minimum bolt length is rounded to thenext longer nominal length increment.
ENGINEERING JOURNAL / SECOND QUARTER / 1996 43
Shading in the table indicates that the combination ofgrip, bolt length, and number of washers is such that the nutmay jamb on the thread run-out; this occurs only for boltslonger than 5 inches (i.e., when ½-in. length increments areused). The use of additional washers, which may alsorequire a longer bolt, is a common solution. Jamming mayoccur when the bolt length minus the threaded lengthexceeds the grip plus the minimum thickness of washer(s)minus an allowance for the elongation of the bolt duringtensioning. For most bolts, a nut rotation of one-half totwo-thirds from snug-tight is required to achieve fulltensioning; longer bolts may require one full turn.Conservatively assuming one full turn, and because the nutsurface is countersunk by approximately one third of onethread pitch, the appropriate allowance (see Appendix) forelongation of the bolt during tensioning is two-thirds of onethread pitch;3 this will be conservative for snug-tightenedbolts, which may have significantly less elongation.
WASHER REQUIREMENTS
RCSC Specification Section 7(c) indicates the cases inwhich 32
5 -in.-thick ASTM F436 washers must be used withASTM A325 and A490 bolts. Such washers are notrequired for these high-strength bolts in standard,oversized, and short-slotted holes except:
1. under the turned element when the bolt is fullytensioned by the calibrated wrench method.
2. under the head and nut when ASTM A490 bolts areused in combination with material with a specifiedyield point below 40 ksi.
3. to cover an oversized or short-slotted hole in anouter ply. For ASTM A490 bolts over 1 inch indiameter through an oversized or short-slotted holein an outer ply, the washer must be 16
5 -in.-thick;
two 325 -in.-thick washers do not meet this
requirement.
Some alternative design fasteners provide a bearing circleon the bolt head and/or nut of diameter equal to or greaterthan the diameter of an ASTM F436 washer. When suchfasteners are used, the need for washers in cases 1 and 2above is eliminated.
When high-strength bolts are used through long-slottedholes in an outer ply, a plate washer with standard holesthat completely covers the slot must be provided; the platewasher must be made from structural grade material with aminimum thickness of 16
5 -in., but need not be hardened.For ASTM A490 bolts over 1 inch in diameter throughlong-slotted holes in an outer ply, single 16
5 -in.-thick
ASTM F436 washers must be used; two 325 -in.-thick
washers do not meet this requirement.
EXCLUDING THREADS FORBEARING X CONNECTIONS
The minimum thickness t of the outer connected ply closestto the nut to exclude threads from the shear plane of the
connection has been tabulated in Table 2. It is calculated asthe grip plus the threaded length minus the bolt length. Adash indicates that, for the given grip, the threads will beexcluded regardless of the actual thickness of the plyclosest to the nut (i.e., t ≤ 0). A common solution when it isdesired to exclude the threads but the minimum thickness isnot present is to use a longer bolt with additional washer(s)under the nut. Nominal dimensions are used in thiscalculation for two reasons: (1) RCSC SpecificationCommentary Section C2 permits thread run-out into theshear plane; and, (2) the control dimension in boltthreading is the distance from the underside of the bolthead to the first useable thread; i.e., the bolt underlengthtolerance is absorbed in the threaded length. In calculatingthe tabulated values of t, washers (if used) are assumed tobe installed under the nut. If washer(s) are present underthe bolt head, their thickness must be added to the tabulatedvalue of t. When a dash is shown and washer(s) are to beplaced under the bolt head, the value of t can be determinedas indicated above; alternatively, the washer thickness maybe considered as part of the grip.
A common rule of thumb2 can be generalized from thetabulated values for minimum outer-ply thickness. With nowashers, the threads will always be excluded from the shearplane (regardless of the grip) for ¾-in. and 8
7 -in. diameter
bolts if the outer ply thickness is not less than 83 -in.; the
same is true for 1-in. and 811 -in. diameter bolts if the outer
ply thickness is not less than ½-in. With one washer underthe nut, these values may be reduced by 8
1 -in. Because thisrule of thumb is based upon the worst case combination ofgrip and bolt length, reference to the tabulated values forlesser outerply thicknesses will often be beneficial.
A supplementary provision has been added to ASTMA325 for full-length threading (ASTM A325T). Thisprovision may be specified for ASTM A325 bolts of lengthless than or equal to four times the bolt diameter only; thereis no similar provision in ASTM A490. Note that if ASTMA325T bolts are specified, it is impossible to exclude thethreads from the shear plane. Thus, for these bolts, thetabulated values of t are meaningless.
ILLUSTRATIVE EXAMPLES
The following examples illustrate the use of Table 2.
Example 1
Given:
Select the bolt length for ¾-in. diameter ASTM A325-Nbolts in standard holes in a 83 -in. single-plate connection
supporting a W21×50 beam (nominal tw= 83 -in.).
Solution:
The grip is 83 + 8
3 = ¾-in. From Table 2, for ¾-in.diameter bolts with zero washers, use 1¾-in. bolt length.
44 ENGINEERING JOURNAL / SECOND QUARTER / 1996
Example 2
Given:
Select the bolt length for ¾-in. diameter ASTM A325-Xbolts in standard holes in a double-angle connection with2L5×3× 16
5 supporting a W27×84 beam (nominal tw = 167 -
in.).
Solution:
The grip is 165 + 16
7 + 165 = 16
11 in. From Table 2, for ¾-in. diameter bolts with zero washers, try 2¼-in. bolt length.Also from Table 2, the minimum thickness of the plyclosest to the nut to exclude the threads is 16
3 -in. Since this
is less than the 165 -in. angle thickness, use 2¼-in. bolt
length.
Example 3
Given:
Select the bolt length for fully tensioned ¾-in. diameterASTM A325-N bolts connecting a ½-in.-thick angle to aW14×500 column flange (nominal tw = 3½ in.). Thecalibrated wrench method will be used to tension the boltsrequiring one washer under the turned element.
Solution:
The grip is ½ + 3½ = 4 in. From Table 2, for ¾-in. diameterbolts with one washer, the table cell is shaded, indicatingthat this combination or grip, number of washers, and boltlength is such that the nut may jamb on the thread run-out.Therefore, try two washers. From Table 2, for ¾-in.diameter bolts with two washers, use 5½-in. bolt length.
Example 4
Given:
Select the bolt length for 87 -in. diameter ASTM A490-Nbolts in standard holes in an extended end-plate momentconnection (1-in. thick) to a W14×132 column flange(nominal tf = 1 in.). The column and end-plate material areASTM A572 grade 50 material. Bolts will be tension-control-type alternative design fasteners.
Solution:
The grip is 1 + 1 = 2 in. From Table 2, for 87 -in. diameter
bolts with zero washers, use 3¼-in. bolt length.
REFERENCES
1. American Institute of Steel Construction, Manual of SteelConstruction—Load and Resistance Factor Design, Volume II—Connections, p. 8-11 and 8-18, Chicago, IL, 1994.
2. Research Council on Structural Connections, Load andResistance Factor Design Specification for Structural JointsUsing ASTM A325 or A490 Bolts, AISC, Chicago, IL, 1988.
3. Industrial Fasteners Institute, Fastener Standards, Sixth Ed.,IFI, Cleveland, OH, 1988.
APPENDIX
The following table is from the RCSC Specification.2
Table C2.To Determine Required Bolt
Nominal Bolt Size, inches Length Add to Grip, In inches
½ 1611
85
87
¾ 1
87
811
1 1¼
811 1½
1¼8
51
831 1¾
1½8
71
The following tables are summarized from FastenerStandards.3
Bolt length toleranceBolt length, in.
Dia., in. 6 or less over 6
¾ –0.19 –0.25
87 –0.19 –0.25
1 –0.19 –0.25
811 –0.25 –0.25
Washer thickness tolerancesWasher thickness, in.
Dia., in. Max. Nom. Min.
¾ 0.17732
5 (0.156) 0.122
87 0.177
325 (0.156) 0.136
1 0.17732
5 (0.156) 0.136
811 0.177
325 (0.156) 0.136
Nut thickness tolerancesNut thickness, in.
Dia., in. Max. Nom. Min.
¾ 0.75864
47 (0.734) 0.710
87 0.885
6455 (0.859) 0.833
1 1.01264
63 (0.984) 0.956
811 1.139
6471 (1.109) 1.079
Allowance for elongation due to full tensioningThreads Thread
Dia., in. per inch pitch, p, in. 2p/3¾ 10 0.100 0.067
87 9 0.111 0.074
1 8 0.125 0.084
811 7 0.143 0.096
ENGINEERING JOURNAL / SECOND QUARTER / 1996 45
Table 1.Bolt, Nut, and Washer Tolerances vs. RCSC Specification Table C2 Allowance
(all values in inches)
Bolts less than or equal to 6-in. long
Tolerances from Appendix RCSC Spec. Table C2 conservative by:
Number of washersBoltDiameter
RCSC Spec.Table C2
AllowanceNut
ThicknessBolt
UnderlengthNut
OverthickWasher
Overthick Zero One Two¾ 1
6447 0.19 0.024 0.021
643
321
641
87
811 64
55 0.19 0.026 0.02164
332
164
1
1 1¼64
63 0.19 0.028 0.02164
332
1 0
811 1½
6471 0.25 0.030 0.021
647
323
161
Bolts over 6-in. long
Tolerances from Appendix RCSC Spec. Table C2 conservative by:
Number of washersBoltDiameter
RCSCTable C2
NutThickness
BoltUnderlength
NutOverthick
WasherOverthick Zero One Two
¾ 164
47 0.25 0.024 0.021 − 164 − 1
32− 3
64
87
811 64
55 0.25 0.026 0.021 − 164 − 1
32− 3
64
1 1¼64
63 0.25 0.028 0.021 − 164 − 1
32− 3
64
811 1½
6471 0.25 0.030 0.021
647
323
161
Shading indicates that RCSC Specification Table C2 values result in negligibly unconservative bolt lengths.
46 ENGINEERING JOURNAL / SECOND QUARTER / 1996
Table 2.ASTM A325 and A490 Bolts with
zero, one, or two 325 -In.-thick washer(s)
¾-in. dia. 78 -in. dia.
no washers 1 washer 2 washers no washers 1 washer 2 washersGrip L , in. t, in. L , in. t, in. L , in. t, in. L , in. t, in. L , in. t, in. L , in. t, in.
½ 1½ 83 1¾ 1
8 2 — 1¾ ¼ 1¾ ¼ 2 —
169 1¾ 16
3 1¾ 316 2 — 1¾ 5
16 2 116 2 1
16
85 1¾ ¼ 1¾ ¼ 2 — 1¾ 3
8 2 18 2¼ —
1611 1¾ 16
5 2 116 2 1
16 2 316 2 3
16 2¼ —
¾ 1¾ 83 2 1
8 2¼ — 2 ¼ 2 ¼ 2¼ —
1613 2 16
3 2 316 2¼ — 2 5
16 2¼ 116 2¼ 1
16
87 2 ¼ 2 ¼ 2¼ — 2 3
8 2¼ 18 2½ —
1615 2 16
5 2¼ 116 2¼ 1
16 2¼ 316 2¼ 3
16 2½ —
1 2 83 2¼ 1
8 2½ — 2¼ ¼ 2¼ ¼ 2½ —
1611 2¼ 16
3 2¼ 316 2½ — 2¼ 5
16 2½ 116 2½ 1
16
811 2¼ ¼ 2¼ ¼ 2½ — 2¼ 3
8 2½ 18 2¾ —
1631 2¼ 16
5 2½ 116 2½ 1
16 2½ 316 2½ 3
16 2¾ —
1¼ 2¼ 83 2½ 1
8 2¾ — 2½ ¼ 2½ ¼ 2¾ —
1651 2½ 16
3 2½ 316 2¾ — 2½ 5
16 2¾ 116 2¾ 1
16
831 2½ ¼ 2½ ¼ 2¾ — 2½ 3
8 2¾ 18 3 —
1671 2½ 16
5 2¾ 116 2¾ 1
16 2¾ 316 2¾ 3
16 3 —
1½ 2½ 83 2¾ 1
8 3 — 2¾ ¼ 2¾ ¼ 3 —
1916 2¾ 16
3 2¾ 316 3 — 2¾ 5
16 3 116 3 1
16
158 2¾ ¼ 2¾ ¼ 3 — 2¾ 3
8 3 18 3¼ —
11116 2¾ 16
5 3 116 3 1
16 3 316 3 3
16 3¼ —
1¾ 2¾ 83 3 1
8 3¼ — 3 ¼ 3 ¼ 3¼ —
11316 3 16
3 3 316 3¼ — 3 5
16 3¼ 116 3¼ 1
16
178 3 ¼ 3 ¼ 3¼ — 3 3
8 3¼ 18 3½ —
11516 3 16
5 3¼ 116 3¼ 1
16 3¼ 316 3¼ 3
16 3½ —
2 3 38 3¼ 1
8 3½ — 3¼ ¼ 3¼ ¼ 3½ —
2 116 3¼ 3
16 3¼ 316 3½ — 3¼ 5
16 3½ 116 3½ 1
16
2 18 3¼ ¼ 3¼ ¼ 3½ — 3¼ 3
8 3½ 18 3¾ —
2 316 3¼ 5
16 3½ 116 3½ 1
16 3½ 316 3½ 3
16 3¾ —
Notes:1. Minimum bolt length calculated per RCSC Specification Table C22. Below 5-in. bolt length, minimum length increment is ¼-in.; otherwise, ½-in.3. When washer(s) are under bolt head, increase t by thickness of washer(s)4. Shaded cells indicate longer bolt and additional washers may be required to prevent nut from jamming on the thread run-out5. "—" indicates that threads are excluded regardless of ply thickness
ENGINEERING JOURNAL / SECOND QUARTER / 1996 47
Table 2.ASTM A325 and A490 Bolts
with zero, one, or two 532 -In.-thick washer(s)
1-in. dia. 118 -in. dia.
no washers 1 washer 2 washers no washers 1 washer 2 washersGrip L , in. t, in. L , in. t, in. L , in. t, in. L , in. t, in. L , in. t, in. L , in. t, in.
½ 1¾ ½ 2 ¼ 2¼ — 2 ½ 2¼ ¼ 2½ —9
16 2 516 2 5
16 2¼ 116 2¼ 5
16 2¼ 516 2½ 1
16
58 2 3
8 2 38 2¼ 1
8 2¼ 38 2¼ 3
8 2½ 18
1116 2 7
16 2¼ 316 2¼ 3
16 2¼ 716 2½ 3
16 2½ 316
¾ 2 ½ 2¼ ¼ 2½ — 2¼ ½ 2½ ¼ 2¾ —13
16 2¼ 516 2¼ 5
16 2½ 116 2½ 5
16 2½ 516 2¾ 1
16
78 2¼ 3
8 2¼ 38 2½ 1
8 2½ 38 2½ 3
8 2¾ 18
1516 2¼ 7
16 2½ 316 2½ 3
16 2½ 716 2¾ 3
16 2¾ 316
1 2¼ ½ 2½ ¼ 2¾ — 2½ ½ 2¾ ¼ 3 —
1116 2½ 5
16 2½ 516 2¾ 1
16 2¾ 516 2¾ 5
16 3 116
118 2½ 3
8 2½ 38 2¾ 1
8 2¾ 38 2¾ 3
8 3 18
1316 2½ 7
16 2¾ 316 2¾ 3
16 2¾ 716 3 3
16 3 316
1¼ 2½ ½ 2¾ ¼ 3 — 2¾ ½ 3 ¼ 3¼ —
1516 2¾ 5
16 2¾ 516 3 1
16 3 516 3 5
16 3¼ 116
138 2¾ 3
8 2¾ 38 3 1
8 3 38 3 3
8 3¼ 18
1716 2¾ 7
16 3 316 3 3
16 3 716 3¼ 3
16 3¼ 316
1½ 2¾ ½ 3 ¼ 3¼ — 3 ½ 3¼ ¼ 3½ —
1916 3 5
16 3 516 3¼ 1
16 3¼ 516 3¼ 5
16 3½ 116
158 3 3
8 3 38 3¼ 1
8 3¼ 38 3¼ 3
8 3½ 18
11116 3 7
16 3¼ 316 3¼ 3
16 3¼ 716 3½ 3
16 3½ 316
1¾ 3 ½ 3¼ ¼ 3½ — 3¼ ½ 3½ ¼ 3¾ —113
16 3¼ 516 3¼ 5
16 3½ 116 3½ 5
16 3½ 516 3¾ 1
16
178 3¼ 3
8 3¼ 38 3½ 1
8 3½ 38 3½ 3
8 3¾ 18
11516 3¼ 7
16 3½ 316 3½ 3
16 3½ 716 3¾ 3
16 3¾ 316
2 3¼ ½ 3½ ¼ 3¾ — 3½ ½ 3¾ ¼ 4 —
2 116 3½ 5
16 3½ 516 3¾ 1
16 3¾ 516 3¾ 5
16 4 116
2 18 3½ 3
8 3½ 38 3¾ 1
8 3¾ 38 3¾ 3
8 4 18
2 316 3½ 7
16 3¾ 316 3¾ 3
16 3¾ 716 4 3
16 4 316
Notes:1. Minimum bolt length calculated per RCSC Specification Table C22. Below 5-in. bolt length, minimum length increment is ¼-in.; otherwise, ½-in.3. When washer(s) are under bolt head, increase t by thickness of washer(s)4. Shaded cells indicate longer bolt and additional washers may be required to prevent nut from jamming on the thread run-out5. "—" indicates that threads are excluded regardless of ply thickness
48 ENGINEERING JOURNAL / SECOND QUARTER / 1996
Table 2.ASTM A325 and A490 Bolts
with zero, one, or two 325 -in.-thick washer(s)
¾-in. dia. 78 -in. dia.
no washers 1 washer 2 washers no washers 1 washer 2 washersGrip L , in. t, in. L , in. t, in. L , in. t, in. L , in. t, in. L , in. t, in. L , in. t, in.
2¼ 3¼ 38 3½ 1
8 3¾ — 3½ ¼ 3½ ¼ 3¾ —
2 516 3½ 3
16 3½ 316 3¾ — 3½ 5
16 3¾ 116 3¾ 1
16
2 38 3½ ¼ 3½ ¼ 3¾ — 3½ 3
8 3¾ 18 4 —
2716 3½ 5
16 3¾ 116 3¾ 1
16 3¾ 316 3¾ 3
16 4 —
2½ 3½ 38 3¾ 1
8 4 — 3¾ ¼ 3¾ ¼ 4 —
2916 3¾ 3
16 3¾ 316 4 — 3¾ 5
16 4 116 4 1
16
2 58 3¾ ¼ 3¾ ¼ 4 — 3¾ 3
8 4 18 4¼ —
21116 3¾ 5
16 4 116 4 1
16 4 316 4 3
16 4¼ —
2¾ 3¾ 38 4 1
8 4¼ — 4 ¼ 4 ¼ 4¼ —
21316 4 3
16 4 316 4¼ — 4 5
16 4¼ 116 4¼ 1
16
278 4 ¼ 4 ¼ 4¼ — 4 3
8 4¼ 18 4½ —
21516 4 5
16 4¼ 116 4¼ 1
16 4¼ 316 4¼ 3
16 4½ —
3 4 38 4¼ 1
8 4½ — 4¼ ¼ 4¼ ¼ 4½ —
3116 4¼ 3
16 4¼ 316 4½ — 4¼ 5
16 4½ 116 4½ 1
16
318 4¼ ¼ 4¼ ¼ 4½ — 4¼ 3
8 4½ 18 4¾ —
3316 4¼ 5
16 4½ 116 4½ 1
16 4½ 316 4½ 3
16 4¾ —
3¼ 4¼ 38 4½ 1
8 4¾ — 4½ ¼ 4½ ¼ 4¾ —
3516 4½ 3
16 4½ 316 4¾ — 4½ 5
16 4¾ 116 4¾ 1
16
338 4½ ¼ 4½ ¼ 4¾ — 4½ 3
8 4¾ 18 5 —
3716 4½ 5
16 4¾ 116 4¾ 1
16 4¾ 316 4¾ 3
16 5 —
3½ 4½ 38 4¾ 1
8 5 — 4¾ ¼ 4¾ ¼ 5 —
3916 4¾ 3
16 4¾ 316 5 — 4¾ 5
16 5 116 5 1
16
358 4¾ ¼ 4¾ ¼ 5 — 4¾ 3
8 5 18 5½ —
31116 4¾ 5
16 5 116 5 1
16 5 316 5 3
16 5½ —
3¾ 4¾ 38 5 1
8 5½ — 5 ¼ 5 ¼ 5½ —
31316 5 3
16 5 316 5½ — 5 5
16 5½ — 5½ —
378 5 ¼ 5 ¼ 5½ — 5 3
8 5½ — 5½ —
31516 5 5
16 5½ — 5½ — 5½ — 5½ — 5½ —
Notes:1. Minimum bolt length calculated per RCSC Specification Table C22. Below 5-in. bolt length, minimum length increment is ¼-in.; otherwise, ½-in.3. When washer(s) are under bolt head, increase t by thickness of washer(s)4. Shaded cells indicate longer bolt and additional washers may be required to prevent nut from jamming on the thread run-out5. "—" indicates that threads are excluded regardless of ply thickness
ENGINEERING JOURNAL / SECOND QUARTER / 1996 49
Table 2.ASTM A325 and A490 Bolts
with zero, one, or two 325 -in.-thick washer(s)
1-in. dia. 118 -in. dia.
no washers 1 washer 2 washers no washers 1 washer 2 washersGrip L , in. t, in. L , in. t, in. L , in. t, in. L , in. t, in. L , in. t, in. L , in. t, in.
2¼ 3½ ½ 3¾ ¼ 4 — 3¾ ½ 4 ¼ 4¼ —
2 516
3¾ 516
3¾ 516
4 116
4 516
4 516
4¼ 116
2 38
3¾ 38
3¾ 38
4 18
4 38
4 38
4¼ 18
2716
3¾ 716
4 316
4 316
4 716
4¼ 316
4¼ 316
2½ 3¾ ½ 4 ¼ 4¼ — 4 ½ 4¼ ¼ 4½ —
2916
4 516
4 516
4¼ 116
4¼ 516
4¼ 516
4½ 116
2 58
4 38
4 38
4¼ 18
4¼ 38
4¼ 38
4½ 18
21116
4 716
4¼ 316
4¼ 316
4¼ 716
4½ 316
4½ 316
2¾ 4 ½ 4¼ ¼ 4½ — 4¼ ½ 4½ ¼ 4¾ —
21316
4¼ 516
4¼ 516
4½ 116
4½ 516
4½ 516
4¾ 116
278
4¼ 38
4¼ 38
4½ 18
4½ 38
4½ 38
4¾ 18
21516
4¼ 716
4½ 316
4½ 316
4½ 716
4¾ 316
4¾ 316
3 4¼ ½ 4½ ¼ 4¾ — 4½ ½ 4¾ ¼ 5 —
3116
4½ 516
4½ 516
4¾ 116
4¾ 516
4¾ 516
5 116
318
4½ 38
4½ 38
4¾ 18
4¾ 38
4¾ 38
5 18
3316
4½ 716
4¾ 316
4¾ 316
4¾ 716
5 316
5 316
3¼ 4½ ½ 4¾ ¼ 5 — 4¾ ½ 5 ¼ 5½ —
3516
4¾ 516
4¾ 516
5 116
5 516
5 516
5½ —
338
4¾ 38
4¾ 38
5 18
5 38
5 38
5½ —
3716
4¾ 716
5 316
5 316
5 716
5½ — 5½ —
3½ 4¾ ½ 5 ¼ 5½ — 5 ½ 5½ — 5½ —
3916
5 516
5 516
5½ — 5½ 116
5½ 116
5½ 116
358
5 38
5 38
5½ — 5½ 18
5½ 18
5½ 18
31116
5 716
5½ — 5½ — 5½ 316
5½ 316
5½ 316
3¾ 5 ½ 5½ — 5½ — 5½ ¼ 5½ ¼ 6 —
31316
5½ 116
5½ 116
5½ 116
5½ 516
5½ 516
6 —
378
5½ 18
5½ 18
5½ 18
5½ 38
5½ 38
6 —
31516
5½ 316
5½ 316
5½ 316
5½ 716
6 — 6 —
Notes:1. Minimum bolt length calculated per RCSC Specification Table C22. Below 5-in. bolt length, minimum length increment is ¼-in.; otherwise, ½-in.3. When washer(s) are under bolt head, increase t by thickness of washer(s)4. Shaded cells indicate longer bolt and additional washers may be required to prevent nut from jamming on the thread run-out5. "—" indicates that threads are excluded regardless of ply thickness
50 ENGINEERING JOURNAL / SECOND QUARTER / 1996
Table 2.ASTM A325 and A490 Bolts
with zero, one, or two 325 -in.-thick washer(s)
¾-in. dia. 78 -in. dia.
no washers 1 washer 2 washers no washers 1 washer 2 washersGrip L , in. t, in. L , in. t, in. L , in. t, in. L , in. t, in. L , in. t, in. L , in. t, in.
4 5 38 5½ — 5½ — 5½ — 5½ — 5½ —
4 116 5½ — 5½ — 5½ — 5½ 1
16 5½ 116 5½ 1
16
4 18 5½ — 5½ — 5½ — 5½ 1
8 5½ 18 6 —
4 316 5½ 1
16 5½ 116 5½ 1
16 5½ 316 5½ 3
16 6 —
4¼ 5½ 18 5½ 1
8 6 — 5½ ¼ 5½ ¼ 6 —
4 516 5½ 3
16 5½ 316 6 — 5½ 5
16 6 — 6 —
4 38 5½ ¼ 5½ ¼ 6 — 5½ 3
8 6 — 6 —
4716 5½ 5
16 6 — 6 — 6 — 6 — 6 —
4½ 5½ 38 6 — 6 — 6 — 6 — 6 —
4916 6 — 6 — 6 — 6 1
16 6 116 6 1
16
4 58 6 — 6 — 6 — 6 1
8 6 18 6½ —
41116 6 1
16 6 116 6 1
16 6 316 6 3
16 6½ —
4¾ 6 18 6 1
8 6½ — 6 ¼ 6 ¼ 6½ —
41316 6 3
16 6 316 6½ — 6 5
16 6½ — 6½ —
478 6 ¼ 6 ¼ 6½ — 6 3
8 6½ — 6½ —
41516 6 5
16 6½ — 6½ — 6½ — 6½ — 6½ —
5 6 38 6½ — 6½ — 6½ — 6½ — 6½ —
5116 6½ — 6½ — 6½ — 6½ 1
16 6½ 116 6½ 1
16
518 6½ — 6½ — 6½ — 6½ 1
8 6½ 18 7 —
5316 6½ 1
16 6½ 116 6½ 1
16 6½ 316 6½ 3
16 7 —
5¼ 6½ 18 6½ 1
8 7 — 6½ ¼ 6½ ¼ 7 —
5516 6½ 3
16 6½ 316 7 — 6½ 5
16 7 — 7 —
538 6½ ¼ 6½ ¼ 7 — 6½ 3
8 7 — 7 —
5716 6½ 5
16 7 — 7 — 7 — 7 — 7 —
5½ 6½ 38 7 — 7 — 7 — 7 — 7 —
5916 7 — 7 — 7 — 7 1
16 7 116 7 1
16
558 7 — 7 — 7 — 7 1
8 7 18 7½ —
51116 7 1
16 7 116 7 1
16 7 316 7 3
16 7½ —
Notes:1. Minimum bolt length calculated per RCSC Specification Table C22. Below 5-in. bolt length, minimum length increment is ¼-in.; otherwise, ½-in.3. When washer(s) are under bolt head, increase t by thickness of washer(s)4. Shaded cells indicate longer bolt and additional washers may be required to prevent nut from jamming on the thread run-out5. "—" indicates that threads are excluded regardless of ply thickness
ENGINEERING JOURNAL / SECOND QUARTER / 1996 51
Table 2.ASTM A325 and A490 Bolts
with zero, one, or two 325 -in.-thick washer(s)
1-in. dia. 118 -in. dia.
no washers 1 washer 2 washers no washers 1 washer 2 washersGrip L , in. t, in. L , in. t, in. L , in. t, in. L , in. t, in. L , in. t, in. L , in. t, in.
4 5½ ¼ 5½ ¼ 6 — 5½ ½ 6 — 6 —
4 116 5½ 5
16 5½ 516 6 — 6 1
16 6 116 6 1
16
4 18 5½ 3
8 5½ 38 6 — 6 1
8 6 18 6 1
8
4 316 5½ 7
16 6 — 6 — 6 316 6 3
16 6 316
4¼ 5½ ½ 6 — 6 — 6 ¼ 6 ¼ 6½ —
4 516 6 1
16 6 116 6 1
16 6 516 6 5
16 6½ —
4 38 6 1
8 6 18 6 1
8 6 38 6 3
8 6½ —
4716 6 3
16 6 316 6 3
16 6 716 6½ — 6½ —
4½ 6 ¼ 6 ¼ 6½ — 6 ½ 6½ — 6½ —
4916 6 5
16 6 516 6½ — 6½ 1
16 6½ 116 6½ 1
16
4 58 6 3
8 6 38 6½ — 6½ 1
8 6½ 18 6½ 1
8
41116 6 7
16 6½ — 6½ — 6½ 316 6½ 3
16 6½ 316
4¾ 6 ½ 6½ — 6½ — 6½ ¼ 6½ ¼ 7 —
41316 6½ 1
16 6½ 116 6½ 1
16 6½ 516 6½ 5
16 7 —
478 6½ 1
8 6½ 18 6½ 1
8 6½ 38 6½ 3
8 7 —
41516 6½ 3
16 6½ 316 6½ 3
16 6½ 716 7 — 7 —
5 6½ ¼ 6½ ¼ 7 — 6½ ½ 7 — 7 —
5116 6½ 5
16 6½ 516 7 — 7 1
16 7 116 7 1
16
518 6½ 3
8 6½ 38 7 — 7 1
8 7 18 7 1
8
5316 6½ 7
16 7 — 7 — 7 316 7 3
16 7 316
5¼ 6½ ½ 7 — 7 — 7 ¼ 7 ¼ 7½ —
5516 7 1
16 7 116 7 1
16 7 516 7 5
16 7½ —
538 7 1
8 7 18 7 1
8 7 38 7 3
8 7½ —
5716 7 3
16 7 316 7 3
16 7 716 7½ — 7½ —
5½ 7 ¼ 7 ¼ 7½ — 7 ½ 7½ — 7½ —
5916 7 5
16 7 516 7½ — 7½ 1
16 7½ 116 7½ 1
16
558 7 3
8 7 38 7½ — 7½ 1
8 7½ 18 7½ 1
8
51116 7 7
16 7½ — 7½ — 7½ 316 7½ 3
16 7½ 316
Notes:1. Minimum bolt length calculated per RCSC Specification Table C22. Below 5-in. bolt length, minimum length increment is ¼-in.; otherwise, ½-in.3. When washer(s) are under bolt head, increase t by thickness of washer(s)4. Shaded cells indicate longer bolt and additional washers may be required to prevent nut from jamming on the thread run-out5. "—" indicates that threads are excluded regardless of ply thickness
52 ENGINEERING JOURNAL / SECOND QUARTER / 1996
Table 2.ASTM A325 and A490 Bolts
with zero, one, or two 325 -in.-thick washer(s)
¾-in. dia. 78 -in. dia.
no washers 1 washer 2 washers no washers 1 washer 2 washersGrip L , in. t, in. L , in. t, in. L , in. t, in. L , in. t, in. L , in. t, in. L , in. t, in.
5¾ 7 18 7 1
8 7½ — 7 ¼ 7 ¼ 7½ —
51316 7 3
16 7 316 7½ — 7 5
16 7½ — 7½ —
578 7 ¼ 7 ¼ 7½ — 7 3
8 7½ — 7½ —
51516 7 5
16 7½ — 7½ — 7½ — 7½ — 7½ —
6 7 38 7½ — 7½ — 7½ — 7½ — 7½ —
6 116 7½ — 7½ — 7½ — 7½ 1
16 7½ 116 7½ 1
16
6 18 7½ — 7½ — 7½ — 7½ 1
8 7½ 18 8 —
6 316 7½ 1
16 7½ 116 7½ 1
16 7½ 316 7½ 3
16 8 —
6¼ 7½ 18 7½ 1
8 8 — 7½ ¼ 7½ ¼ 8 —
6 516 7½ 3
16 7½ 316 8 — 7½ 5
16 8 — 8 —
6 38 7½ ¼ 7½ ¼ 8 — 7½ 3
8 8 — 8 —
6716 7½ 5
16 8 — 8 — 8 — 8 — 8 —
6½ 7½ 38 8 — 8 — 8 — 8 — 8 —
6916 8 — 8 — 8 — 8 1
16 8 116 8 1
16
6 58 8 — 8 — 8 — 8 1
8 8 18
61116 8 1
16 8 116 8 1
16 8 316 8 3
16
6¾ 8 18 8 1
8 8 ¼ 8 ¼
61316 8 3
16 8 316 8 5
16
678 8 ¼ 8 ¼ 8 3
8
61516 8 5
16
7 8 38
Note: bolt lengths exceeding 8 inches are not generally available except by special order
Notes:1. Minimum bolt length calculated per RCSC Specification Table C22. Below 5-in. bolt length, minimum length increment is ¼-in.; otherwise, ½-in.3. When washer(s) are under bolt head, increase t by thickness of washer(s)4. Shaded cells indicate longer bolt and additional washers may be required to prevent nut from jamming on the thread run-out5. "—" indicates that threads are excluded regardless of ply thickness
ENGINEERING JOURNAL / SECOND QUARTER / 1996 53
Table 2.ASTM A325 and A490 Bolts
with zero, one, or two 325 -in.-thick washer(s)
1-in. dia. 118 -in. dia.
no washers 1 washer 2 washers no washers 1 washer 2 washers
Grip L , in. t, in. L , in. t, in. L , in. t, in. L , in. t, in. L , in. t, in. L , in. t, in.
5¾ 7 ½ 7½ — 7½ — 7½ ¼ 7½ ¼ 8 —513
16 7½ 116 7½ 1
16 7½ 116 7½ 5
16 7½ 516 8 —
578 7½ 1
8 7½ 18 7½ 1
8 7½ 38 7½ 3
8 8 —
51516 7½ 3
16 7½ 316 7½ 3
16 7½ 716 8 — 8 —
6 7½ ¼ 7½ ¼ 8 — 7½ ½ 8 — 8 —6 1
16 7½ 516 7½ 5
16 8 — 8 116 8 1
16 8 116
6 18 7½ 3
8 7½ 38 8 — 8 1
8 8 18 8 1
8
6 316 7½ 7
16 8 — 8 — 8 316 8 3
16 8 316
6¼ 7½ ½ 8 — 8 — 8 ¼ 8 ¼6 5
16 8 116 8 1
16 8 116 8 5
16 8 516
6 38 8 1
8 8 18 8 1
8 8 38 8 3
8
6716 8 3
16 8 316 8 3
16 8 716
6½ 8 ¼ 8 ¼ 8 ½69
16 8 516 8 5
16
6 58 8 3
8 8 38
61116 8 7
16
6¾ 8 ½
Note: bolt lengths exceeding 8 inches are not generally available except by special order
Notes:1. Minimum bolt length calculated per RCSC Specification Table C22. Below 5-in. bolt length, minimum length increment is ¼-in.; otherwise, ½-in.3. When washer(s) are under bolt head, increase t by thickness of washer(s)4. Shaded cells indicate longer bolt and additional washers may be required to prevent nut from jamming on the thread run-out5. "—" indicates that threads are excluded regardless of ply thickness
54 ENGINEERING JOURNAL / SECOND QUARTER / 1996