CHAPTER 8 - RIVETS AND FASTENERS Flashcards by Abi Faulkner

INTRODUCTION
How are rivets always supplied to the operator?

With one head already formed and the shank bare to permit insertion

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INTRODUCTION
In what documents are the appropriate rivets found for repairs?

Appropriate repair scheme e.g Topic 6

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INTRODUCTION
What are the most common rivets made from?
What other materials can be used?

Most common: Aluminium Alloy
Other Metals: Steel, Tungum, Monel, Nickel Alloy, Copper

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INTRODUCTION
What 3 properties of a rivet effect it’s strength?

Their size, type of head and the material they’re made from

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INTRODUCTION
Which is the strongest out of the types of rivets?
Also specify an advantage of the other two…

-Strongest are the Snap Head rivets due to size and material
-Second strongest: mushroom head - good holding so usually used on external skinning
-Countersunk-head: although weaker, provide a huge advantage for aerodynamics and aircraft performance due to flush external jointing

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CLASSES AND CONSTRUCTION
Specify the three classes used in aviation rivets and fasteners

Solid rivets: strongest of the rivet fasteners - normally used when access to both sides of the work is possible
Blind Expansion rivets: used when only one side of the work is accessible
Special Purpose fasteners: used where a greater shear or tensile strength, or other special property is required

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CLASSES AND CONSTRUCTION
What information about a rivet is given by their specification references?

Head form, material and size

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CLASSES AND CONSTRUCTION
What is rivet size based on?

By the diameter of the shank
It’s overall length

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CLASSES AND CONSTRUCTION
Describe what would happen in these join considerations:
1. If the rivets are too close together
2. If the rivets are too far apart
3. If the rivets are too close to the edge

Too close —> excess number of rivet holes will cause the metal to weaken
Too far —> not sufficient amount of them to take the load applied to the structure, as well as not being effectively weather sealed
Too close to the edge —> allows them to tear through the metal under load

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ABBREVIATIONS
What do these mean when appearing in the repair procedure:
D L P Gauge

D: Nominal Rivet Diameter
L: Land - distance from the entire of the rivet hole to the edge of the plate/skin
P: Pitch - the distance between the centres of adjacent rivet holes
Gauge: thickness of the metal sheet given in millimetres, thousands of an inch or SWG

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HOLE DIMENSIONS
Define the term Clearance in riveting..
What happens if this is too small or too big

This is the space surround the rivet and the edge of the hole, it allows for the expansion of the rivet.
Too small: the sheets can twist
Too big: sheets could move apart

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SOLID RIVETS
Define the term Allowance in riveting..

The length of the shank which comes out of the hole

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SOLID RIVETS
Unless specified otherwise, what is the usual allowance for a ‘reaction’ rivet?

FOLLOW UP: With the dimension, would would the thickness usually be once formed

1.5D
Thickness: 0.5D

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SOLID RIVETS
Why should you never cut rivets to length?

Ruins the finish on the rivet tail which can cause crack after it is formed

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SOLID RIVETS
What is Squeeze riveting? And how is it different from the normal procedure?

When rivets are closed by hydraulically or pneumatically operated machines or tools
Different as the rivets are squeezed and not hit

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SOLID RIVETS
Where is the squeeze riveting procedure used?

Where the honeycomb panels are part of the structure

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SOLID RIVETS
What shape is the dolly used on countersunk-head rivets?

Crowned - so the edges don’t make contact with the airframes skin

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SOLID RIVETS
What is the maximum and minimum width allowed for formed rivets? What should the thickness also be?

Minimum: 1.33D
Maximum: 1.5D
Thickness: 0.5D

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SOLID RIVETS
At what percentage of swelling is a rivet usually at once formed correctly?

50%

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SOLID RIVETS
What device can be used to check for a correct diameter of a formed head?

GO/NO GO Gauge

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SOLID RIVETS
How could over-panning effect the surrounding metal?

Initiate cracks around the hole

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SOLID RIVETS
List 3 things that should be checked when inspecting formed rivets..

Rivets are tight and correctly formed
Rivet heads have no damage or cracks
Adjacent area has not been damaged by tools

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MBC LOCK CREATOR FASTENERS
What does the MBC lock creator rivet have, which forms the rivet lock installation?

A driving anvil

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MBC LOCK CREATR FAsTENERS
What measurements can a single pulling head be used to install?

3.2mm
4.0mm
4.8mm

MBC LOCK CREATOR FASTENERS Which pliers are used for the above fasteners?

AVDEL pliers

MBC LOCK CREATOR FASTENERS These rivets are supplied lubricated, should this be removed?

MBC LOCK CREATOR FASTENERS How do you know installation is complete with these rivets?

When the stem breaks off flush with the head of the rivet

MBC LOCK CREATOR FASTENERS Which two loose articles break off from this rivet once installation is complete?

Pulling stem Driving anvil

CHERRYMAX RIVETS Name the 5 main parts of a Cherrymax rivet..

Hollow rivet sleeve Serrated stem Shear ring Locking collar Stem cone

CHERRYMAX RIVETS Cherrymax rivets are supplied lubricated, should this be removed?

CHERRYMAX RIVETS When being installed, what happens when the break notch in the rivet stem is in line with the locking recess in the rivet sleeve?

1. The locking collar is automatically put in 2. The rivet stem shears off level with the top of the rivet head

CHERRYMAX RIVETS Why are nominal and oversize Cherrymax rivets not interchangeable?

Due to the difference in the necessary hole diamter

HI-LOK FASTENERS What 2 parts are the hi-lok made up of?

Pin and collar

HI-LOK FASTENERS How is the hi-lok installed?

A Allen key is held against the pin whilst the collar is tightened. The hexagonal nut breaks off when the correct torque value is applied.

HI-LOK FASTENERS Why are these fasteners not true blind rivets?

Although one person can form them, access to both sides is still required

HI-LOK FASTENERS What diameters are these fasteners available in?

From 3.2mm to 9.2mm

HI-LOK FASTENERS How is the hi-lock colour coded?

Red for the aluminium alloy collar Natural Steel for stainless steel pin

HI-LOK FASTENERS What is the adjustment lowed in material without a change in pin length?

+ 1.6mm -

VISU LOK II BLIND BOLT Which fastener is a corrosion-resisting steel blind fastener?

VISU LOK II BLIND BOLT

VISU LOK II BLIND BOLT What is an alternate fastener for the above?

Jo-Bolts

REMOVING BURRS What does debarring accomplish?

Removes all rough edges (burrs) and unwanted material (swarf)

REMOVING BURRS What tool is used to remove burrs?

De-burring tool

COUNTERSINKING When can you countersink (instead of dimpling)?

When the sheet metal thickness is greater than the depth of the rivet head

COUNTERSINKING What process is used if countersinking cannot be done?

Dimpling

COUNTERSINKING What is done is the sheet are of different thicknesses?

Dimple made in the thin sheet Countersinking made in the thick sheet

COUNTERSINKING What is the countersinking tool made up of?

A centralising spigot An adjustable depth stop

COUNTERSINKING What tools are used for dimpling?

A punch and a setting block A different tool required for each different countersink angle

COUNTERSINKING Compared to the hole, how big should the diameter of the dimpling punch pilot be?

The same

COUNTERSINKING Name 4 things that should be inspected before a rivet is installed…

1. Holes are circular and 90 degrees to the surface 2. Diameter is correct for the type of rivet 3. Sharp does are made smooth 4. Countersink is at the centre of the hole and cut to the correct angle 5. Countersink has sufficient depth 6. Dimple has no marks and is correct angle 7. Surfaces touch without distortion and the same shape as the adjacent area 8. Burrs and swarf is removed 9. Surface treatment is examined and repaired is necessary

REMOVAL OF SOLID RIVETS What should you think about before removing rivets?

1. Thickness and strength of the surrounding structure 2. Procedure which will cause the least damage

REMOVAL OF SOLID RIVETS What should be checked before a rivet is reinstalled?

Diameter of the hole is within limits

REMOVAL OF SOLID RIVETS Explain the usual procedure for removing a solid rivet..

Mark the head with a centre-punch Drill to the depth of the head Remove the head with a pin-punch (or a flat chisel as last resort) Rivet removed with a parallel punch (make sure the skin is support from behind)

REMOVAL OF SOLID RIVETS What should you not do when removing solid rivets?

Make the hole larger or cause damage to surrounding structure Put on a shear load

REMOVAL OF BLIND RIVETS Why are Cherrymax rivets so difficult to remove?

They contain a steel collar which physically locks the rivet stem in place

REMOVAL OF BLIND RIVETS How should a Cherrymax rivet be removed? How does this differ with a countersink Cherrymax?

File the universal head cherrymax rivet until the steel collar is removed Use a punch to remove the stem Countersink: small drill is used to drill into the stem Hole is increased to the rivet shank diameter and the lock collar lifted out

REMOVAL OF BLIND RIVETS How do you remove a blind rivet?

Head is drilled off with a drill the same diameter as the hole Remaining part is removed with a punch

RIVET CALCULATION What is length measured in? What is diameter measured in? (Inches)

Length: 1/16 of an inch Diameter: 1/32 of an inch

SOLID RIVETS What rivets can be used in squeeze riveting as an alternate to solid rivets?

AVDEL rivets

SOLID RIVETS How heavy is an average block used when forming a 3.2mm rivet?

Approximately 1kg