How to tighten a bolt
Ryan's way: Spin nut on bolt then tighten.
Engineer's way (ODOT Spec book 2005)
513.20 High-Strength Steel Bolts, Nuts, and Washers. Provide high-strength
steel bolts, nuts, and washers conforming for all bolted connections including erection
bolts for cross frames and lateral bracing to 711.09.
A. General. Provide the Engineer with access to the work for observing the
installation and the tightening and checking of the bolts.
Determine the required bolt length by adding the value from Table 513.20-1
to the grip. The table values include an allowance for manufacturing tolerances
and provide a bolt length for threads to protrude through the nut. Add 5/32 inch (4
mm) for each hardened flat washer used and 5/16 inch (8 mm) for each beveled
washer used. Adjust the length, as determined by Table 513.20-1, to the next
longer 1/4 inch (6 mm); when installed, the end of the bolt shall be flush with or
project several thread lengths outside the face of the nut.
TABLE 513.20-1
Bolt Size To determine required bolt Length, add to grip[1]
(inches) (inches)
1/2 11/16
5/8 7/8
3/4 1
7/8 1 1/8
1 1 1/4
1 1/8 1 1/2
1 1/4 1 5/8
1 3/8 1 3/4
1 1/2 1 7/8
[1] Total thickness of all connected material excluding washers.
TABLE 513.20-1M
Bolt Size To determine required bolt length, add to grip[1]
(mm) (mm)
M16 24
M20 28
M22 31
M24 35
M27 38
M30 41
M36 47
[1] Total thickness of all connected material excluding washers.
Use bolts, nuts, and washers with a residual coating of lubricant when received.
Bolts, nuts, and washers without their original lubrication shall not be
used.
B. Preparation. With the exception of metalizing, galvanizing, and both organic
zinc and inorganic zinc primers, remove coatings from joint surfaces, including
surfaces adjacent to the bolt heads, nuts, and washers. Remove lacquer, dirt,
oil, loose scale, rust, burrs, pits, and other substances or defects that prevent solid
seating of the parts or interfere with the development of complete frictional contact.
Do not place gaskets or other yielding material between joint surfaces.
C. Installation. For each bolt, place a hardened washer under the element (nut
or bolt head) turned in tightening. If an outer face of the bolted parts has a slope of
more than 1:20 with respect to a plane normal to the bolt axis, use a smooth beveled
washer to compensate for the lack of parallelism.
If necessary, the Contractor may clip washers, at one location, not closer than
seven-eighths of the bolt diameter from the center of the washer.
During final assembly of the parts to be bolted, first install a sufficient number
of drift pins to provide and maintain accurate alignment of holes and parts,
then a sufficient number of bolts tightened to a snug tight condition to bring all the
parts of the joint into complete contact. Replace any bolts that were installed before
installing drift pins. Before releasing the member from the hoisting equipment,
fill half the holes with drift pins and bolts tightened to a snug tight condition
in at least 50 percent of the holes (preferably, half pins and half bolts) but use at
least two drift pines in each flange and web of each beam or girder. Install bolts
starting at the most rigidly fixed or stiffest point and progress toward the free
edges.
Use cylindrical drift pines that are not more than 1/32 inch (0.8 mm) smaller
than the hole diameter.
Bolts are snug tight when an impact wrench begins to impact the nut or when
a man applies full effort using an ordinary spud wrench.
Install bolts in the remaining open holes and tighten the bolts to a snug tight
fit, after which all bolts shall be tightened completely by the turn-of-nut method.
Where difficulty is experienced with the fit of the connection and the bolts
are used to draw the elements into contact, check all bolts in the affected portion of
the connection for a sustained snug tight condition.
Replace drift pins with completely tightened bolts only after all the remaining
holes are filled with completely tightened bolts.
Do not field ream holes drilled full size during fabrication.
After bolts are snug tight, the wrench operator shall match-mark the outer
face of the nut with the flush or protruding portion of the bolt using a crayon or
paint. The Engineer will use the match-marks to determine the relative rotation
between the bolt and nut during final tightening using the turn-of-the-nut method.
Commence tightening at the most rigidly fixed or stiffest point and progress
toward the free edges, both in the initial snugging up and in the final tightening. If
required because of wrench operation clearances, tightening may be done by turning
the bolt. If used, provide impact wrenches of adequate capacity to perform the
required tightening each bolt in approximately 10 seconds.
Do not reuse galvanized A 325 bolts. Re-tightening previously tightened
bolts that became loose by tightening adjacent bolts is not reuse.
Follow the additional bolting requirements in 513.26.
D. Bolt Tension. When all bolts in the joint are tight, the minimum bolt tension
for each bolt size is shown in Table 513.20-2.
TABLE 513.20-2
Bolt Size (inches) Bolt Tension[1] (kips), minimum A 325
1/2 12
5/8 19
3/4 28
7/8 39
1 51
1 1/8 56
1 1/4 71
1 3/8 85
1 1/2 103
[1] Equal to 70 percent of specified minimum tensile strengths of bolts,
rounded off to the nearest kip.
TABLE 513.20-2M
Bolt Size (mm) Bolt Tension[1] (kN), minimum A 325M
M16 91
M20 142
M22 176
M24 206
M27 267
M30 327
M36 475
[1] Equal to 70 percent of specified minimum tensile strengths of bolts,
rounded off to the nearest kN.
TABLE 513.20-3 NUT ROTATION FROM SNUG TIGHT CONDITION
Disposition of Outer Faces of Bolted Parts
Bolt Length (as measured
from underside of head
to extreme end of
point)
Both faces
normal to
bolt axis
One face normal to
bolt axis and other
face sloped not more
than 1:20 (bevel
washer not used)
Both faces sloped
not more than
1:20 from normal
to bolt axis (bevel
washer not used)
Up to and including 4
diameters 1/3 turn 1/2 turn 2/3 turn
Over 4 diameters but not
exceeding 8 diameters 1/2 turn 2/3 turn 5/6 turn
Over 8 diameters but not
exceeding 12 diameters 2/3 turn 5/6 turn 1 turn
Attain the bolt tension specified in Table 513.20-2 by tightening all bolts, the
applicable amount of nut rotation specified in Table 513.20-3 by the turn-of-nut
method.
Nut rotation is relative to bolt, regardless of the element (nut or bolt) being
turned. Tighten bolts requiring 1/2 turn and less within �30 degrees and tighten
bolts requiring 2/3 turn and more within �45 degrees.
