Metallic Structures

Question 1

For maximum strength of a formed sheet metal fitting, should the bend be made along or across the grain of the metal?

Answer 1

Across the grain

Question 2

What determines the minimum bend radius that can be used when forming a sheet metal structural fitting?

Answer 2

The alloy, the metal thickness, and its hardness

Question 3

What is meant by the neutral axis in a sheet of metal?

Answer 3

A plane within the metal that neither stretches nor shrinks when the metal is being bent

Question 4

what is a mold line in the development of a flat pattern for a formed metal part?

Answer 4

An extension of the flat sides beyond the radius

Question 5

What is the bend tangent line?

Answer 5

a line in a flat pattern layout at which the bend starts

Question 6

what is meant by setback?

Answer 6

The distance the jaws of a brake must be set back from the mold line to form a bend

Question 7

What is meant by bend allowance?

Answer 7

The actual amount of metal in a bend. It is the distance between the bend tangent lines in a flat pattern layout

Question 8

What is a sight line?

Answer 8

A line drawn on a sheet metal layout that is one bend radius from the bend-tangent line

Question 9

What is the main function of throatless shears in an aircraft sheet metal shop?

Answer 9

Throatless shears are used to cut mild carbon steel up to 10-gauge, and stainless steel up 12-gauge. They can be used to cut irregular curves in the metal

Question 10

What kind of metal forming is done by a slip roll former?

Answer 10

Simple curves with a large radius

Question 11

What kind of metal forming is done by bumping?

Answer 11

Compound curves in sheet metal

Question 12

When forming a curved angle, what must be done to the flanges?

Answer 12

The flanges must be stretched for a convex and shrunk for a concave curve

Question 13

When hand-forming a piece of sheet metal that has a concave curve, should the forming be started in the center of the curve, or at its edges?

Answer 13

Start at the edges and work toward the center

Question 14

What is meant by a joggle in a piece of sheet metal?

Answer 14

A joggle is a small offset near the edge of a piece of sheet metal that allows the sheet to overlap another piece of metal

Question 15

What type of device is a Cleco fastener?

Answer 15

A patented fastener that is inserted in the rivet holes and used to hold two pieces of sheet metal together until they can be held together

Question 16

what type of rivet may be used to replace a round head rivet in an aircraft structure

Answer 16

A universal head rivet

Question 17

How long should a rivet be to join two pieces of sheet metal?

Answer 17

The combined thickness of the metal sheets plus 1-1/2 times the rivet shank diameter

Question 18

How can rivets be physically identified for part number and type of material?

Answer 18

The identifying mark on the head of an aluminum alloy rivet indicates the specific alloy used in the manufacture of the rivet

Question 19

Name several methods for forming sheet metal

Answer 19

1. Bending or folding
2. Stretching
3. Shrinking
4. Bumping
5. Crimping

Question 20

What are the dimensions of a properly formed rivet head?

Answer 20

The head should be 1 1/2 times the shank diameter in width and 1/2 the shank diameter in height

Question 21

Describe the markings found on the heads of A, B, D, AD, and DD rivets

Answer 21

A: Plain
B: Cross
D: A raised dot
AD: A dimple
DD: Double dash

Question 22

What happens to the stem of a self-plugging (friction lock) rivet when the rivet is installed?

Answer 22

The stem is pulled until it snaps off and the remaining projecting part is trimmed flush with the head

Question 23

Name at least three types of self-plugging mechanical lock rivets

Answer 23

1. CherryMAX
2. CherryLOCK
3. OLYMPIC-LOK
4. HuckLOK

Question 24

what is the difference between the tools required to pull a CherryLock rivet and CherryMAX rivet?

Answer 24

CherryLOCK rivets require a tool for each different size and head shape, while one pulling tool will set any size CherryMAX rivet

Question 25

Which of the five stresses is the most common cause of rivet failure?

Answer 25

Shear

Question 26

If a 2024 rivet must be replaced with a 2117 rivet, how do you determine the size to be used?

Answer 26

For a 5/32” or smaller diameter, use the next larger size 2117 rivet, assumin that the edge distance and spacing meet the minimum requirements

Question 27

Describe the process for determining the total length of a solid rivet for a particular installation

Answer 27

Add the grip length (thickness of the materials being joined) plus 1 1/2 times the rivet diameter

Question 28

What type of damage can occur when using a rivet set that does not properly fit the rivet?

Answer 28

If the radius of the set is too small, the rivet head may be damaged, whereas a set with an over-sized radius may cause damage to the sheet metal

Question 29

Why is it important to use the proper size and weight bucking bar when performing sheet metal riveting?

Answer 29

If a bucking bar is too large or heavy, it may be difficult to control and may cause damage to the surrounding structure, whereas a bucking bar that is too light will not properly upset the rivet before work hardening occurs

Question 30

What are the two special calculations that must be made when bending sheet metal?

Answer 30

Bend allowance and setback

Question 31

What factors must be considered in order to determine setback?

Answer 31

Thickness of the metal and bend radius

Question 32

What is done to a corner where two bends intersect to prevent cracking?

Answer 32

Relief holes are drilled in the corner

Question 33

What are two reasons for installing a lightening hole in a sheet metal wing rib?

Answer 33

Lightening holes reduce the weight and increase stiffness

Question 34

Describe a joggle and explain its function

Answer 34

A joggle is an offset formed at an intersection of two or more sheets of metal to allow multiple sheets to be stacked flat against each other