Chapter 2 - Sheet Metal Structures - Oral Questions

Question 1

What is the major type of damage to aluminum structures that is caused by exposure to the weather?

Answer 1

Corrosion

Question 2

Name several methods for forming sheet metal.

Answer 2

Bending or folding ,

stretching,

shrinking,

bumping, and

crimping

Question 3

What are the dimensions of a properly formed rivet head?

Answer 3

The head should be 1.5 times the shank diameter in width and 1/2 the shank diameter in height

Question 4

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

Answer 4

A rivets are plain, B rivets have a cross, D rivets have a raised dot, AD rivets have a dimple, and DD rivets have a double dash

Question 5

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

Answer 5

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

Question 6

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

Answer 6

CherryMAX, CherryLOCK, OLYMPIC-LOK, and HuckLok

Question 7

What is the difference between the tools required to pull a cherryLOCK rivet and a CherryMAX rivet?

Answer 7

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

Question 8

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

Answer 8

Shear

Question 9

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

Answer 9

For 5/32” or smaller diameter, use the next larger size, as long as edge distance and spacing meet minimums

Question 10

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

Answer 10

1.5 times the rivet diameter plus the grip length

Question 11

What minimum edge distance and spacing should be used for a single row of protruding head rivets?

Answer 11

At least two rivet diameters from the edge and not less than three rivet diameters apart.

Question 12

How can a mechanic determine whether the countersink for a flush rivet should be dimpled or drilled?

Answer 12

By the thickness of the top sheet- thin sheets are dimpled while thick sheets may be countersunk

Question 13

What action is taken to prevent cracks from forming while dimpling magnesium or some hard sheet metals?

Answer 13

Hot dimpling equipment is used to preheat and soften the metal before the dimple is formed

Question 14

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

Answer 14

If the radius of the rivet set is too small, the rivet head may be damaged. If it is too large, the sheet metal may be damaged.

Question 15

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

Answer 15

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

Question 16

What procedures should be followed to properly remove a solid-shank rivet?

Answer 16

Center punch the rivet and then drill just to the base of the rivet head with the same size or one size smaller drill. Once drilled, use a pin punch to tip off the rivet head and drive the remaining shank out of the hole while supporting the surrounding metal

Question 17

What two calculations must be made when bending sheet metal?

Answer 17

Setback and bend allowance

Setback (SB)—the distance the jaws of a brake must be
setback from the mold line to form a bend. In a 90° bend,
SB = R + T (radius of the bend plus thickness of the metal). The K-factor must be used for all bends that are smaller or larger than 90°. SB = K(R+T)

Bend allowance (BA)—refers to the curved section of
metal within the bend (the portion of metal that is curved in
bending).

Question 18

What factors must be considered to determine setback?

Answer 18

Bend radius and material thickness

The distance the jaws of a brake must be set back
from the mold line to form a bend. Setback for a 90° bend
is equal to the inside radius of the bend plus the thickness of
the metal being bent. For a bend other than 90°, a K-factor
must be used. See also K-factor.

SB=(R+T)K

Question 19

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

Answer 19

relief holes are drilled in the corner

Question 20

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

Answer 20

Lightening holes reduce the weight and increase stiffness

Question 21

Describe a joggle and explain its function

Answer 21

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

Question 22

When repairing an all-metal aircraft, how do you determine what metals should be used?

Answer 22

Always use metal of the same type and thickness as the original structure