National Crane Published 8-01-2017 Control # 287-11 4-39
NBT40 SERVICE MANUAL BOOM MAINTENANCE
TORQUE VALUES for Second Nut:
Inch Series with Coarse Threads (UNC)
Five Section Top/bottom Pad Replacement,
Assembled Boom
Inspect top and bottom wear pads periodically for signs of
abrasion or excessive wear.
Excessive wear is wear in excess of 3/16 in from original
thickness (1st, 2nd and 3rd stage bottom pads are 29.8mm
(1.17 in) thick, 4th stage bottom pads are 11.6mm (.45 in)
thick, 2nd 4th and 5th stage top pads are 11.6 (.45 in) thick,
3rd stage top pads are 25.4mm (1.0 in) thick, or uneven wear
such as the outside edge of the pad worn in excess of 3/32 in
deeper than the inside edge of the pad. If any of these
conditions are found, the top and bottom pads may be
replaced without disassembly of the boom.
Also, if the boom extension operates erratically or during
replacement of top and bottom pads, it is recommended that
Cable end
Thread Size
Minimum
Nut
Strength
GRADE
Nut Type
TORQUE
ft lbf
1/2-13 SAE 2
Hex Jam
(HALF)
12
5/8-11 SAE 2
Hex Jam
(HALF)
31
3/4-10 SAE 2
Hex Jam
(HALF)
47
7/8-9 SAE 2
Hex Jam
(HALF)
63
1-8 SAE 2
Hex Jam
(HALF)
199
1 ¼-7 SAE 2
Hex Jam
(HALF)
203
1 ½-6 SAE 5
Hex Jam
(FULL)
250
1 ¾-5 ASTM B
Hex Jam
(FULL)
250
SCRIBE MARKS WHERE BOOM
SECTIONS BOTTOM OUT
5TH STAGE
4TH STAGE
2ND STAGE
5/4/3 RETRACT CABLES
4/3/2 RETRACT CABLES
3/2/1 RETRACT CABLES
3RD STAGE
3/4/5 EXTEND CABLES
1/2/3 EXTEND CABLES
2/3/4 EXTEND CABLES
FIGURE 4-12
Reference Only
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