National Crane 600H, Service Manual

Page: 98 / 232

BOOM 600H SERVICE MANUAL
4-24
08-19-2022 Control # 092-13
TORQUE VALUES for Second Nut:
Inch Series with Coarse Threads (UNC)
Metric Series with Coarse Threads
LIFT CYLINDER REPAIR
Lift Cylinder Disassembly
1. Disconnect shaft end of cylinder from machine.
2. Retract cylinder shaft with oil from the hydraulic system
until about 12 in (30 cm) of shaft is extended. The barrel
must be filled with oil to prevent a compressed air
chamber being formed which could result in injury at
disassembly.
3. Remove the cylinder from the machine and place on
supports with an oil pan directly beneath the cylinder
head area.
4. Using the proper size of external snap ring pliers,
expand the snap ring completely and remove from
groove. Slide large washer forward to gain access to the
packing gland.
5. Using a special drive tool, drive the packing gland into
the barrel assembly to expose the round cross section
retaining ring. Then use a small needle nose locking
plier to clamp the round cross section retaining ring to
prevent it from rotating in the groove. Use two straight
blade screw drivers: one to pry the end of the ring out of
the groove and the other to pry the ring out of the barrel
assembly.
6. Attach a porta-power hand pump or hydraulic line from
crane circuit valve to the shaft end of the cylinder. De-
burr ring groove edge. Failure to do so will damage
barrel or packing gland.
7. Operate hand pump or crane circuit valve, preferably the
boom telescope circuit, to force packing gland out of
barrel.
8. Remove holding valve from cylinder to allow removal of
shaft and piston assembly. Remove the shaft and piston
assembly by hand.
9. Disassemble the piston set by removing nut, replace
worn or damaged parts. Note: Loctite 680 is used during
original assembly to secure nut to shaft. If necessary,
heat nut to 400-500° F (204-260°C) to facilitate removal.
If heat is necessary for removal, discard nut and replace
with new equivalent nut as well as worn or damaged
parts.
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
Cable end
Thread Size
Minimum
Nut
Property
Class
Nut Type
TORQUE
Nm
M16x2 5
Hex Jam
(THIN)
26
M20x2.5 5
Hex Jam
(THIN)
66
REFERENCE ONLY