Metallic Structure 2

A single-lap sheet splice is to be used to repair a section of damaged aluminum skin. If a double row of 1/8-inch rivets is used, the minimum allowable overlap will be

• 1 1/2 inch
• 3/4 inch
• 13/16 inch
• 1 inch

Answer explanation

The minimum overlap for a single-lap splice with two rows of rivets is found using the formula (4D + 2-1/2D). For 1/8" rivets, this equals 13/16 inch.

When drilling stainless steel, the drill used should have an included angle of

• 90° and turn at a low speed

• 118° and turn at a high speed

• 140° and turn at a low speed

• 135° and turn at a high speed

Answer explanation

When drilling stainless steel, a drill with a 140° included angle is optimal for reducing friction and heat. It should be operated at a low speed to prevent overheating and ensure a clean cut, making this the correct choice.

What is the minimum spacing for a single row of aircraft rivets?

• Two times the diameter of the rivet shank

• Three times the length of the rivet shank

• Three times the diameter of the rivet shank

• Four times the diameter of the rivet shank

Answer explanation

The minimum spacing for a single row of aircraft rivets is three times the diameter of the rivet shank. This ensures adequate strength and prevents material failure, making 'three times the diameter' the correct choice.

If a streamline cover plate is to be hand formed using a form block, the bumping operation should be

• distributed evenly over the face of the aluminum at all times

• started by tapping the aluminum lightly around the edges and gradually working down into the center

• started by tapping the aluminum in the center until it touches the bottom

• started at the deepest point

Answer explanation

The correct approach is to start by tapping the aluminum lightly around the edges and gradually work down into the center. This method ensures even distribution of pressure, preventing distortion and achieving a smooth form.

You can distinguish between aluminum and aluminum alloy by

• filing the metal

• testing with an acetic acid solution

• testing with a 10 percent solution of caustic soda

• smelling the metal

Answer explanation

Testing with a 10 percent solution of caustic soda can reveal differences in reactivity between aluminum and aluminum alloys, as alloys may contain elements that react differently compared to pure aluminum.

A piece of flat stock that is to be bent to a closed angle of 15° must be bent through an angle of

• 165°
• 105°
• 90°
• 15°

Answer explanation

A closed angle of 15° means the metal is bent "shut" to 15°, requiring a bend of 165° (180 - 15).

The sharpest bend that can be placed in a piece of metal without critically weakening the part is called the

• bend allowance

• minimum radius of bend

• maximum radius of bend

• setback

Answer explanation

The minimum radius of bend refers to the sharpest bend that can be made in metal without causing critical weakening. This is crucial for maintaining the integrity of the material during bending processes.

When bending metal, the material on the outside of the curve stretches while the material on the inside compresses. That part of the material which is not affected by either stress is the

• mold line

• bend tangent line

• neutral line

• setback line

Answer explanation

The neutral line is the part of the material that experiences no tensile or compressive stress during bending. It remains unchanged in length, while the outer material stretches and the inner material compresses.

Alloy 2117 rivets are heat treated

• by the manufacturer and do not require heat treatment before being driven

• by the manufacturer but require reheat treatment before being driven

• to a temperature of 910 to 930°F and quenched in cold water

• by the mechanic on site

Answer explanation

Alloy 2117 rivets are pre-heat treated by the manufacturer, meaning they are ready for use without any additional heat treatment before being driven. This makes the correct choice the first option.

The primary alloying agent of 2024-T3 is indicated by the number

• 2.0

• 20.0

• 24.0

• 3.0

Answer explanation

The primary alloying agent in 2024-T3 is copper, which corresponds to the first digit '2' in the alloy designation. Therefore, the correct answer is 2.0.