7.8 Riveting Flashcards
What are solid shank rivets?
Solid shank rivets are the most common type of rivet found in aircraft construction. They are used to join aircraft structures and are low cost as well as one of the oldest and most reliable types of fasteners.
What are the characteristics of solid shank rivets?
Solid shank rivets are permanent fasteners, quicker to install than a nut & bolt, and can be installed using high-speed installation tools.
When should rivets not be used?
Rivets must not be used in thick materials or where the load is subject to tension, as their tensile strengths are low relative to their shear strength.
What happens to riveted joints without sealants?
Riveted joints are not airtight or watertight unless sealants are used.
How are rivets removed?
Since rivets are permanently installed, they must be removed by drilling them out.
What are the three types of riveted joints used in aircraft?
The three different types of riveted joints are lap joints, flush joints, and joggle joints.
What factors govern the strength of a riveted joint?
The factors that govern the strength of a joint are material specification, rivet specification, and rivet spacing.
What are lap joints?
Lap joints have their skin riveted together, resulting in a distinct step or change in levels, and are not aerodynamically smooth.
Where are lap joints generally used?
Lap joints are generally used on light aircraft where aerodynamic smoothness is not as critical.
What are flush joints?
Flush joints are used to obtain aerodynamic smoothness between two skins, with both skins riveted to the same substructure.
What is a flush patch repair?
A flush patch repair is an example of a flush joint, maintaining aerodynamic smoothness by riveting the skin with an insert of the same thickness.
What are joggle joints?
A joggle joint is a combination of a flush and a lap joint, where one skin is joggled to accommodate the other to produce one smooth side.
What is rivet spacing?
Rivet spacing is the distance between fastener rows, typically taken from the hole centres, and is usually 4 to 5D.
What is the pitch of a fastener?
The pitch of any fastener is the distance from the centre of one fastener hole to the centre of the next fastener hole in a row, quoted in terms of the fastener nominal shank diameter D.
What is edge margin in fasteners?
Edge margin is the distance from the centre of the fastener hole to the nearest edge of a sheet, and is generally 2D to 2.5D times the diameter of the rivet.
What is the sphere of influence of a rivet?
The sphere of influence is the area of sheet metal over which a rivet achieves a watertight joint, typically 5D.
What is inter-rivet buckling?
Inter-rivet buckling occurs when incorrectly widely-spaced rivets allow a panel to deform between the rivets, which can be minimized by closely spacing the rivets.
What tools are required for installing a rivet?
Tools include drills, reamers, rivet cutters, bucking bars, riveting hammers, draw sets, dimpling equipment, countersinking equipment, rivet guns, and rivet squeezers.
What is the purpose of a rivet cutter?
A rivet cutter is used to cut rivets to a required length when a rivet of the required length is unavailable.
How do you use a rotary rivet cutter?
Insert the rivet in the correct diameter hole, place the required number of shims under the rivet head, and squeeze the cutter like pliers.
What caution should be taken when using a rivet cutter?
Using a rivet cutter can leave burrs and sharp edges, which can cause scratches and personal injury.
What is a bucking bar?
A bucking bar is a heavy steel tool used during rivet installation to set the shop head (tail) of the rivet.
What are the weight ranges for bucking bars?
Bucking bars range from 0.5 kg to 4.5 kg (1.1 lbs to 9.92 lbs).
What material are bucking bars typically made from?
Bucking bars are made from low carbon steel that has been case hardened.
What is the importance of the face of the bucking bar?
The face must be hard enough to resist indentation but not too hard to shatter.
What is the operation of a bucking bar during riveting?
The bucking bar is held against the shank end of the rivet while the shop head is being formed, at right angles to the rivet shank.
What can cause defective rivet heads?
Defective rivet heads can result from improper vibrating action, using a bucking bar that is too light or heavy, and not holding the bar at right angles.
What is a pneumatic rivet gun?
The pneumatic rivet gun is the most common tool used for upsetting rivets in airframe repair work.
What air pressure do pneumatic rivet guns operate at?
Pneumatic guns operate with an air pressure of approximately 92 - 99 PSI (6.3 - 6.8 Bar).
How long does it take to upset a rivet with a rivet gun?
A rivet gun upsets a rivet in one to three seconds.
What should be done before testing the rivet gun adjustments?
Always test the rivet gun on a piece of wood and adjust the air valve to a comfortable setting.
What are rivet sets or headers?
Rivet sets or headers are interchangeable components designed to fit the type of rivet and location of the work.
What is the function of a rivet shaver?
A rivet shaver is used to ensure aerodynamic smoothness by cutting countersunk rivets to specific tolerances.
What types of countersink tools are available?
Countersink tools come in angles of 82°, 100°, or 120°, with the 100° angle being the most commonly used.
What is the preferred tool for countersinking?
The microstop countersink is preferred for its adjustable sleeve cage that functions as a limit stop.
What are skin pins used for?
Skin pins are temporary fasteners used to hold sheets of metal together during repairs or modifications.
What are Cleco fasteners?
Cleco fasteners are temporary fasteners that hold parts together before they are permanently joined.
What are the common sizes of Cleco fasteners?
Common sizes include 3/32 (#40), 1/8 (#30), 5/32 (#21), and 3/16 (#10), each color-coded for easy recognition.
What are Cleco wing nut fasteners used for?
Cleco wing nut fasteners are used to temporarily fasten metal sheets when higher clamp-up pressure is required.
What are gripper/skin pins?
Gripper pins function like Cleco pins but can be inserted and tightened by hand.
What is the purpose of holding the pilot steady when countersinking thin sheet material?
To ensure accuracy and stability during the countersinking process.
What should be done before countersinking?
Pilot drill an undersized hole, countersink, and then enlarge the hole to final size.
What is the preferred tool for countersinking?
Microstop Countersink.
What features does a Microstop Countersink have?
It has an adjustable sleeve cage that functions as a limit stop and holds the revolving countersink in a vertical position.
What is the requirement for the pilot in a Microstop Countersink?
The pilot must be approximately 0.002 in (0.051 mm) smaller than the hole size.
What should be done before countersinking replacement parts or aircraft skin?
It is recommended to test adjustments on a piece of scrap material.
When is freehand countersinking required?
Where a microstop countersink cannot fit.
What is dimpling?
Shaping a skin or material to accept the head of a countersunk fastener using a male and female die.
What are the three methods of dimpling?
Coin dimpling, radius dimpling, and hot dimpling.
Describe coin dimpling.
A male die fits through the rivet hole, and the coining ram exerts controlled pressure to forge the edges of the hole.
What is a characteristic of coin dimpling?
It gives the hole sharply defined edges that closely resemble machine dimpling.
What is radius dimpling?
The pilot on the male die presses into the female die, forming a dimple without parallel sides.
What is a limitation of radius dimpling?
These dimples cannot be nested.
What is hot dimpling?
A process where material is heated to prevent cracking during dimpling of brittle materials.
What materials typically require hot dimpling?
Magnesium and some harder aluminium alloys, such as AA7075.
How is the hot dimpling process controlled?
The amount of heat and duration applied is carefully controlled to prevent destroying the temper condition of the metal.
What must be inspected before declaring an aircraft serviceable?
All installed rivets must be inspected to ensure structural strength.
What does the inspection of rivets consist of?
Examining the shop and manufactured heads of the rivet and the surrounding skin and structural parts for damage.
What tool can be used to check the condition of a driven rivet head?
A rivet gauge can be used to check the condition of the driven rivet head.
What must be ensured about rivet heads after they are driven?
Rivet heads must not be deformed or cracked, and the surrounding area must be free from distortion.
What should be done if a rivet is deformed and does not meet standards?
It must be replaced with the next larger size, 1/32 in (0.79 mm) in greater diameter.
What should be considered before rejecting rivets?
The strength requirements of the joint and the effectiveness of the rivets.
When is flushness tolerance for countersunk rivets checked?
It is normally checked before riveting commences.
What can sometimes be permitted after riveting for solid rivet heads?
Microshaving can be permitted to obtain a uniform aerodynamic smoothness finish.
What is unacceptable in rivet installation?
Any cracks in the rivet head are not acceptable.
What happens if the holes are not square or misaligned?
The rivet can form with a gap under the head, causing stress in the joint.
What occurs if a rivet is driven into an oversized hole?
The rivet swells into the hole, resulting in an undersized driven head.
What is ‘flash’ in rivet installation?
Excess material that forms around a driven snap head if the rivet allowance is too large.
What can cause a bell-shaped head on a rivet?
If the bucking bar is too light or not held firmly against the rivet.
What usually causes diagonal cracks on a driven head?
Over-driving the rivet.
What can cause gaps between parts during riveting?
Foreign material such as swarf or burrs around holes.
What can happen if parts are not tightly clamped before riveting?
A shanked rivet can form.
What can occur if parts are not held tightly together when drilled?
The holes may misalign or the skin can buckle.
What happens if the bucking bar is not held square to the rivet?
The driven head can become stepped or dragged sideways.
What occurs if the rivet snap is too large?
A flat forms on the manufactured head, and the edges can cut into the structure’s surface.
What happens if the rivet snap is too small?
The snap edges cut into the manufactured head.
What can happen if the rivet snap is not placed squarely?
It can cut into the head and damage the surrounding structure.
