Chevrolet 1980 Light Duty Truck Repair Manual page 416

10-2 METRIC A N D FASTENER INFO RM A TIO N
REUSE OF PREVAILING TORQUE NUT(S) A N D BOLT(S)
PREVAILING TORQUE NUTS
INCORPORATE A SYSTEM TO DEVELOP AN INTERFERENCE
BETWEEN NUT AND BOLT THREADS INTERFERENCE IS MOST
COMMONLY ACHIEVED BY DISTORTING TOP OF ALL-METAL
NUT, BUT ALSO MAY BE ACHIEVED BY DISTORTING AT
MIDDLE OF HEX FLAT, BY NYLON PATCH ON THREADS, BY
NYLON WASHER INSERT AT TOP OF NUT AND BY NYLON
INSERT THROUGH NUT.
PREVAILING TORQUE NUTS
t i D 2 5
TOP LOCK MANY
TYPES
NYLON
INSERT
NYLON
WASHER
INSERT
RECOMMENDATIONS FOR REUSE
A. CLEAN. UNRUSTED PREVAILING TORQUE BOLTS AND NUTS MAY BE REUSED AS
FOLLOWS:
1. CLEAN DIRT AND OTHER FOREIGN MATERIAL OFF NUT AND BOLT.
2. INSPECT BOLT AND NUT TO ASSURE THERE ARE NO CRACKS. ELONGATION OR
OTHER SIGNS OF ABUSE OR OVERTIGHTENINC. LIGHTLY LUBRICATE THREADS. (IF
ANY DOUBT. REPLACE WITH NEW PREVAILING TORQUE FASTENER OF EQUAL OR
GREATER STRENGTH.)
3. ASSEMBLE PARTS AND START BOLT OR NUT.
4. OBSERVE THAT BEFORE FASTENER SEATS. IT DEVELOPS PREVAILING TORQUE PER
CHART BELOW. (IF ANY DOUBT. INSTALL NEW PREVAILING TORQUE FASTENER OF
EQUAL OR GREATER STRENGTH).
5. TIGHTEN TO TORQUE SPECIFIED IN SERVICE MANUAL.
B BOLTS AND NUTS WHICH ARE RUSTY OR DAMAGED SHOULD BE REPLACED WITH NEW
NUTS AND
ALL METAL BOLTS
ADHESIVE OR NYLON
COATED BOLTS
NUTS AND
ALL METAL BOLTS
ADHESIVE OR NYLON
COATED BOLTS
ARE THOSE NUTS WHICH
CED
CENTER
LOCK
NYLON
PATCH
6 & 6.3
N
mii 0.4
In. Lbs.
4.0
N
mii
0.4
In. Lbs.
4.0
.250 .312
N
mii
0.4 0.6
In. Lbs.
4.0 5.0
N
mii
0.4 0.6
In. Lbs.
4.0 5.0
PREVAILING TORQUE BOLTS ARE THOSE BOLTS WHICH
INCORPORATE A SYSTEM TO DEVELOP AN INTERFERENCE
BETWEEN BOLT AND NUT OR TAPPED HOLE THREADS.
INTERFERENCE IS ACHIEVED BY DISTORTING SOME OF THE
THREADS (SEVERAL METHODS
NYLON PATCH OR STRIP OR BY ADHESIVE COATING ON
THREADS.
PREVAILING TORQUE BOLTS
DRY ADHESIVE COATING
Q T ) Q
Z J
NYLON STRIP OR PATCH
METRIC SIZES
8 10 12
" >
~ )
0.8 1.4
18
7.0 12
0.6 1.2 1.6
5.0 10 14
INCH SIZES
.437 .500
.375
2.4
1.4 1.8
15 20
12
1.4 1.8
1.0
12 15
9.0
EXIST), BY APPLYING A
OUT OF ROUND THREAD AREA
(Q
THREAD PROFILE DEFORMED
14 16 20
3.0 4.2 7.0
25 35 57
3.4
2.4 5.6
20 28 46
.562 .625 .750
3.2 4.2 6.2
27 35 51
3.4
2.6 5.2
T - >
28
43