Ingersoll Rand Impact Driver 3940 User Manual

10569408  
Edition 1  
January 2006  
Air Impact Wrench  
Series 3940, 3942 & 3955  
Maintenance Information  
Save These Instructions  
 
9. Remove two Air Port Gaskets (29) and Air Port Gasket  
Retainers (28) from Housing.  
WARNING  
Disassembly of the Handle  
The following procedure requires the use of heat. Take  
all necessary precautions to prevent burns. Carefully  
heat alternate sides of Housing until it is very warm.  
Using thick, heavy gloves to avoid being burned, grasp  
Housing and repeat attempt to dislodge Cylinder.  
1. Clamp Trigger Handle Assembly in leather-covered or copper-  
covered vise jaws with the Straight Inlet (10) upward.  
2. Using a wrench, unscrew and remove Inlet as well as Air Strainer  
Screen (9) and valve Spring (8).  
3. Remove Throttle Valve Assembly (6) and Valve Plunger (5) from  
Handle.  
4. If Trigger (3) must be removed, use an arbor press to push Trigger  
Pin (4) from the Handle and slide Trigger out of slot in Handle.  
8. Open a set of vise jaws wide enough to clear hub of Front End Plate  
and sharply rap hub end of end plate on top of jaws to dislodge Front  
Rotor Bearing.  
Assembly  
General Instructions  
1. Always press on the inner ring of a ball-type bearing when installing  
the bearing on a shaft.  
2. Always press on the outer ring of a ball-type bearing when installing  
the bearing into a bearing recess.  
3. Whenever grasping a tool or part in a vise, always use leather-  
covered or copper-covered vise jaws. Take extra care with threaded  
members and housings.  
4. Always clean every part and wipe every part with a thin film of oil  
before installation.  
9. Coat inside of Cylinder and Rotor (22) with a light film of oil and insert  
the splined hub of Rotor through Cylinder into Front End Plate.  
10. Coat each Vane (23) with a light film of oil and insert a Vane into each  
slot in the Rotor. Vanes must be installed with curved edge toward  
center of Rotor. Spin the Rotor to settle Vanes in position.  
11. Using long tee hex wrench to align hole in Rear End Plate (20) with  
hole in Cylinder, insert the Rear End Plate, bronze face leading, into  
Motor Housing against the Cylinder. End Plate is properly seated  
when large trailing face of End Plate is slightly below face of Motor  
Housing.  
5. Apply a film of O-ring lubricant to all O-rings before final assembly.  
12. Grease Rear Rotor Bearing (18) and install it in recess of Rear End  
Plate.  
Assembly of the Handle  
13. Remove alignment pin from assembled motor and install Cylinder  
Dowel (19). The Dowel is properly seated when end of Dowel does  
not protrude above End Plate.  
14. Install Motor Clamp Washer(s) (16) against Rear End Plate so that  
large outer edge of Washer contacts End Plate.  
1. Position Trigger (3) in Handle (1) and using an arbor press, push  
Trigger Pin (4) full length into Handle so that it captures Trigger.  
2. Clamp Handle in leather-covered or copper-covered vise jaws with  
air inlet opening upward.  
3. Coat Throttle Valve Plunger (5) with oil and insert it, rounded end  
leading, into the inlet hole in Handle.  
Assembly of the Reverse Valve  
4. Install a new Throttle Valve Seal (7) on Throttle Valve (6) and insert  
assembly, Valve Seal leading, into inlet hole in Handle.  
5. Encircle cone end of Air Strainer Screen (9) with large end of Throttle  
Valve Spring (8) and insert both parts, Spring leading, into the inlet  
hole in Handle.  
1. Inject a small amount of grease into hole in Motor Housing (26)  
where Reverse Lock Plunger (30) will be installed. With grease to  
hold them in position, install Reverse Lock Plunger Spring (31) and  
Lock Plunger.  
6. Install Straight Inlet (10) over Strainer Screen in Handle and tighten  
Inlet between 50 and 60 ft-lb (68 and 81 Nm) torque.  
2. Install a new Reverse Valve Bushing Seal (14) in annular groove on  
Reverse Valve (13).  
7. Remove Handle from vise and test Trigger. If Trigger functions  
properly, place assembled Handle aside. If it does not function  
properly, disassemble Handle to determine cause of problem.  
3. Coat Reverse Valve with a light film of oil and install it in Motor  
Housing with the side hole nearest to Seal pointed toward Rotor (22).  
4. Position Reverse Lever (12) on Reverse Valve and while using a thin  
blade screwdriver to depress Reverse Lock Plunger, push Lever onto  
Reverse Valve.  
Assembly of the Motor  
5. Place a new Handle Gasket (17) on the Motor Housing.  
6. Examine Reverse Valve Seal (11) located inside Handle and if it is  
nicked, deformed or worn, remove it and install a new Seal.  
7. Fill rotor cavity in Handle with recommended grease and position  
Handle on the Motor Housing.  
8. For 3940 and 3942 Series: Install four Handle Cap Screws (15) and  
using an alternate tightening pattern, tighten Screws to between 10  
and 12 ft-lb (14 and 16 Nm) torque.  
For 3955 Series: Install four Handle Cap Screws (15) and using an  
alternate tightening pattern, tighten Screws to between 25 and 28 ft-  
lb (34 and 38 Nm) torque.  
9. Move Reverse Lever through the forward and reverse positions to  
make certain the Lever locks in position.  
1. Lightly clamp Motor Housing (26) in leather-covered or copper-  
covered vise jaws with handle end upward.  
NOTICE  
Excessive clamping pressure will distort the Motor  
Housing and make motor installation extremely difficult.  
Do not insert the hammer case end of the Motor  
Housing more than 1” (25 mm) into the vise jaws.  
2. Grease Front Rotor Bearing (25) and install it in recess of Front End  
Plate.  
3. Coat inside surface of Housing and outer edge of  
Front End Plate (24) with a light film of oil.  
10. Turn assembly in vise jaws and clamp on Handle with rotor shaft  
upward.  
4. Using a long tee hex wrench as an alignment pin, insert Front End  
Plate, copper face trailing, into Motor Housing. Align dowel hole in  
End Plate with dowel hole at the bottom of motor bore.  
5. Lubricate and insert a new fiber Air Port Gasket Retainer (28) in one  
of the air ports inside Motor Housing.  
11. Pack Front Rotor Bearing with additional grease and rotate rotor  
shaft. If shaft does not rotate smoothly, rap end of rotor shaft with a  
soft hammer to set motor and try to rotate shaft again.  
6. Install an Air Port Gasket (29) in the air port against Gasket Retainer  
with flat end of Gasket away from Retainer.  
7. Repeat Steps 5 and 6 to install remaining Gasket and Retainer in the  
other air port.  
8. Coat outside of Cylinder (21) with a light film of oil and using long tee  
hex wrench as an alignment pin to align the holes in Cylinder with  
holes in Front End Plate and Housing, insert Cylinder into Housing.  
10569408_ed1  
3
 
1. Coat Hammers (37) with a light film of Ingersoll-Rand Impactool  
Grease No. 170.  
Assembly of the Impact Mechanism  
2. Replace Hammers in Hammer Frame (35) exactly as they were  
when you marked them prior to disassembly.  
NOTICE  
If you are installing new Hammers, or want to change  
the location of the existing Hammers to utilize both  
impacting surfaces, slide the Hammers in the Hammer  
Frame so that the half-round notch on one Hammer is  
located on one side of the Frame and the half-round  
notch on the other Hammer is located on the other side  
of the Frame.  
3. Replace Hammer Pins (36).  
4. Examine base of Anvil (38) and note its contour. While looking down  
through Hammer Frame, swing the top Hammer to its full extreme  
one way or another until you can match the contour of the Anvil.  
Enter the Anvil into the Hammer Frame and through the first  
Hammer. Swing the bottom Hammer in opposite direction from the  
top Hammer and maneuver Anvil slightly until it drops into bottom  
Hammer.  
TOP HAMMER  
WIDE BEVEL UP  
TOP HAMMER  
HALF–ROUND NOTCH ON  
Assembly of the Impactool  
RIGHT  
1. Set assembled hammer mechanism onto rotor shaft spline.  
2. Place Hammer Case Gasket (34) over mechanism and against face  
of Motor Housing.  
3. Grease Anvil and top of Hammer Frame.  
4. Place Hammer Case (39) over mechanism assembly against  
Gasket.  
5. Assemble Dead Handle (43) to Dead Handle Bracket (42). Insert two  
Hammer Case Cap Screws (41). Position assembly against Hammer  
Case and thread the Screws into Housing.  
BOTTOM HAMMER  
WIDE BEVEL DOWN  
6. For 3940 and 3942 Series: Thread remaining two Cap Screws into  
Housing and using an alternating pattern for all four fasteners, tighten  
Screws between 20 and 25 ft-lb (27 and 34 Nm) torque.  
For 3955 Series: Thread remaining two Cap Screws into Housing  
and using an alternating pattern for all four fasteners, tighten Screws  
between 35 and 40 ft-lb (47 and 54 Nm) torque.  
BOTTOM HAMMER  
HALF–ROUND NOTCH ON LEFT  
7. Install a new Exhaust Silencer (33) in Motor Housing Assembly (26)  
and install the Exhaust Deflector (32).  
(Dwg. TPD652)  
Troubleshooting Guide  
Trouble  
Probable Cause  
Solution  
Low power  
Dirty Inlet Bushing or Air Strainer Screen and/or  
Exhaust Silencer.  
Using a clean, suitable, cleaning solution, in a well ventilated  
area, clean Air Strainer Screen, Inlet Bushing and Exhaust  
Silencer.  
Worn or broken Vanes.  
Replace the complete set of Vanes.  
Worn or broken Cylinder and/or scored End Plates.  
Examine the Cylinder and replace it if it is worn or broken or  
if the bore is scored or wavy. Replace the End Plates if they  
are scored.  
Dirty motor parts.  
Disassemble tool and clean all parts with a suitable cleaning  
solution, in a well-ventilated area. Reassemble tool as  
instructed in this manual.  
Improper positioning of the Reverse Valve.  
Incorrect assembly of the motor.  
Make certain that the Reverse Valve is fully engaged to the  
left or right.  
Motor will not run  
Disassemble the motor and replace worn or broken parts  
and reassemble as instructed.  
Insufficient lubricant in the impact mechanism.  
Broken or worn impact mechanism parts.  
Impact Mechanism not assembled correctly.  
Remove the Hammer Case Assembly and lubricate the  
impact mechanism.  
Tool will not impact  
Remove the Hammer Case and examine the impact  
mechanism parts. Replace any worn or broken parts.  
Refer to Assembly of the Impact Mechanism.  
Related Documentation  
For additional information refer to:  
Air Impact Wrench Product Safety Information Manual 04580916.  
Air Impact Wrench Product Information Manuals 10569382 and 80160716.  
Air Impact Wrench Parts List Manuals 10569390 and 80160724.  
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Notes  
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Notes  
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Notes  
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© 2006 Ingersoll-Rand Company  
 

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