7.8 Riveting Flashcards
What are the different types of rivets and joints?
Rivets: Solid shank rivets
Joints: Lap joints, Flush joints, Joggle joints
What is the most common type of rivet found in aircraft construction?
Solid shank rivets
What are the advantages of solid shank rivets?
- Low cost
- Quick installation
- Reliability
What must rivets not be used in?
Thick materials or where the load is subject to tension
What must be done to remove rivets?
They must be drilled out
What are the three different types of riveted joints used in aircraft?
- Lap joints
- Flush joints
- Joggle joints
What factors govern the strength of a riveted joint?
- Material Specification
- Rivet Specification
- Rivet Spacing
How are lap joints characterized?
Skins are riveted together with a distinct step or change in levels
What is the aerodynamic characteristic of lap joints?
Not aerodynamically smooth
What is the purpose of flush joints?
To obtain aerodynamic smoothness between two skins
What is a flush patch repair?
Riveting the skin with an insert of the same thickness using a doubler
What defines a joggle joint?
A combination of a flush and a lap joint
What is the purpose of rivet spacing?
To provide the joint with optimum strength characteristics
What is pitch in the context of rivet spacing?
The distance from the centre of one fastener hole to the centre of the next fastener hole
What is the typical measurement for edge margin?
2D to 2.5D times the diameter of the rivet
What is the sphere of influence of a rivet?
The area over which a rivet achieves a watertight joint, typically 5D
What can inter-rivet buckling cause?
The panel to pull away from a stringer, former, or rib
Fill in the blank: The edge distance is measured from the edge of the _______ to the edge of the plate.
fastener hole
True or False: Riveted joints are typically airtight or watertight.
False
What must be referenced for correct rivet pitch?
Structural Repair Manual (SRM)
What are the tools used for riveting and dimpling?
- Drills
- Reamers
- Rivet cutters
- Bucking bars
- Riveting hammers
- Draw sets
- Dimpling tools
- Countersinking equipment
- Rivet guns
- Rivet squeezers
What is the purpose of a rivet cutter?
To cut rivets to a required length when a rivet of the required length is unavailable
What is a bucking bar also known as?
Dolly or riveting block
What is the weight range of bucking bars?
0.5 kg - 4.5 kg (1.1 lbs - 9.92 lbs)
What material is a bucking bar typically made from?
Low carbon steel that has been case hardened
What is the function of a pneumatic rivet gun?
To upset rivets during airframe repair work
What is the typical air pressure range for pneumatic rivet guns?
92 - 99 PSI (6.3 - 6.8 Bar)
What are rivet sets also known as?
Headers or snaps
What are the two types of rivet squeezers?
- Hand-held riveting
- Pneumatic riveting
What is the primary use of skin pins?
To hold sheets of metal together temporarily during repairs or modifications
What is the function of Cleco fasteners?
To temporarily hold parts together before they are permanently joined
What types of fasteners are used for higher clamp-up pressure?
Cleco wing nut fasteners
What is a rivet shaver used for?
To ensure aerodynamic smoothness of the skin by cutting countersunk rivets within a specific tolerance
What are the common angles for countersink tools?
- 82°
- 100°
- 120°
What type of countersink is preferred for aluminium?
Six fluted countersink
Fill in the blank: A _______ is used to cut rivets to the required length.
rivet cutter
True or False: A bucking bar should be held at an angle to the rivet shank.
False
What is the function of the pneumatic riveting gun’s air-driven hammer?
To supply the force to buck the rivet
What should be done to remove burrs left by a rivet cutter?
Use a file to remove any burred and/or silvered edges
What is the maximum time limit for driving rivets to prevent work hardening?
Three seconds
What is the significance of the weight of a bucking bar?
It helps in the riveting process by allowing the weight to do most of the work
What are the common sizes and colors for Gripper/Skin Pins?
- 3/32” (Red)
- 1/8” (Yellow)
- 5/32” (Blue)
- 3/16” (Black)
- 1/4” (White)
What should be done before adjusting a rivet shaver?
Adjustments must always be made first on scrap material
What is the purpose of backup material when countersinking thin sheet material?
To hold the pilot steady
What can cause defective rivet heads?
- Lack of proper vibrating action
- Using a bucking bar that is too light or too heavy
- Failure to hold the bucking bar at right angles to the rivet
What is the most common problem encountered when hand countersinking?
Chattering
Chattering occurs when the cutting tool vibrates during the countersinking process.
What are some precautions to eliminate or minimize chatter when countersinking?
- Use sharp tooling
- Use a slow speed and steady firm pressure
- Use a piloted countersink with a pilot approximately 0.002 in (0.051 mm) smaller than the hole
- Use backup material to hold the pilot steady when countersinking thin sheet material
- Use a cutter with a different number of flutes
- Pilot drill an undersized hole, countersink, and then enlarge the hole to final size
These precautions help maintain stability and precision during the countersinking process.
What is the preferred tool for countersinking?
Microstop Countersink
The microstop countersink features an adjustable sleeve cage that functions as a limit stop.
What is a key feature of the microstop countersink?
It has an adjustable sleeve cage that holds the revolving countersink in a vertical position
The threaded and replaceable cutters can have either a removable or an integral pilot.
What should the pilot of a microstop countersink be in relation to the hole size?
Approximately 0.002 in (0.051 mm) smaller than the hole size
Testing adjustments on scrap material is recommended before actual countersinking.
What is dimpling?
Shaping a material to accept the head of a countersunk fastener using a male and female die
Dimpling is used when a skin or material is too thin to cut a countersink.
Name the three methods of dimpling.
- Coin dimpling
- Radius dimpling
- Hot dimpling
Each method has different applications based on material thickness and properties.
What is the process of coin dimpling?
A male die fits through the rivet hole while the coining ram exerts controlled pressure on the underside of the hole
This method forges the edges of the hole to fit the shape of the dies.
What is the main characteristic of radius dimpling?
The dimple formed does not have parallel sides, and the lower side has an angle greater than 100°
This makes radius dimples unsuitable for nesting.
What is the purpose of hot dimpling?
To prevent cracking in brittle materials like magnesium and certain aluminium alloys during the dimpling process
Heating the material allows it to soften, reducing the risk of cracks.
True or False: The equipment used for hot dimpling is different from that used for coin or radius dimpling.
False
The equipment is similar, but the dies are heated during hot dimpling.
Why must an inspection of riveted joints take place?
To ensure the structural strength in a repair before declaring the aircraft or component serviceable.
Inspection includes examining rivet heads and surrounding areas for damage.
List some causes of unsatisfactory riveting.
- Misalignment of holes
- Oversized holes
- Foreign materials like swarf or burrs
- Insufficient clamping of parts
- Incorrect use of the bucking bar
- Improper rivet snap size or shape
What must be checked when inspecting rivet heads?
Rivet heads must not be deformed or cracked, and the surrounding area must be free from distortion.
Ensure the area is undamaged by riveting tools.
What should be done with rivets that are deformed and do not meet standards?
They must be replaced with the next larger size, 1/32 in (0.79 mm) in greater diameter.
Replacement may cause more damage if rivets are only slightly below the required standard.
What is the purpose of a rivet gauge?
To check the condition of the driven rivet head for proper dimensional requirements.
What is the consequence of a gap under the rivet head?
It can cause stress in the joint and allow corrosive agents to attack the material.
What happens if a rivet is formed in an oversized hole?
The rivet swells into the hole, resulting in an undersized driven head.
What is ‘flash’ in the context of rivets?
Excess material that forms around a driven snap head if the rivet allowance is too large.
What can cause the driven head of a rivet to become bell-shaped?
If the bucking bar is too light or is not held firmly against the rivet.
What typically causes diagonal cracks on the driven head of a rivet?
Over-driving of the rivet.
What should be done to prevent gaps between parts during riveting?
Ensure that holes are properly de-burred and that any swarf is removed before assembly.
What is a shanked rivet?
A rivet that forms if the parts to be riveted are not tightly clamped before riveting.
What can occur if parts are not held tightly together when drilled?
Holes can misalign or the skin can buckle during riveting.
What happens if the bucking bar is not held square to the rivet?
The driven head can become stepped or dragged sideways.
What can occur if the rivet snap is too large?
A flat can form on the manufactured head, and the edges can cut into the structure’s surface.
What is the effect of a rivet snap that is too small?
The snap edges can cut into the manufactured head, damaging it.
True or False: A rivet snap not placed squarely can damage the surrounding structure.
True.
