Sheet Metal Structures Oral

Front 1

What is the grip length of a rivet?

Back 1

The grip length is the combined thickness of the materials to be joined by the rivet.

Front 2

Where are special rivets, such as Huck or Cherry lock rivets, used?

Back 2

They are used in places where access to both sides of the riveted structure is impossible, or where limited space will not permit the use of a bucking bar. These rivets require special tools, installation, and removal procedures. They are commonly called blind rivets.

Front 3

What is bonded honeycomb (sandwich) construction?

Back 3

It is a laminar construction consisting of a combination of alternating dissimilar materials, assembled, and fixed in relation to each other so that the properties of each can be used to attain specific structural advantages for the whole assembly.

Front 4

What types of materials are used in honeycomb construction?

Back 4

Honeycomb construction may employ stainless steel, titanium, magnesium, plywood, resin-impregnated paper, glass, nylon, or cotton cloth in various combinations.

Front 5

Where are sandwich construction assemblies used?

Back 5

They are used for such areas as bulkheads, control surfaces, fuselage panels, wing panels, radomes, empennage skins, or shear webs.

Front 6

What procedures should be used to prevent damage to the hole when drilling through Plexiglas?

Back 6

The Plexiglas should be backed with wood and the feed slowed as the drill point breaks through the underside of the sheet. A drill that is to be used for this purpose should be modified to a 60° tip angle, the cutting edge to a zero rake angle, and the back lip clearance angle increased to 12 to 15 degrees.

Front 7

What calculation must be made when bending sheet metal?

Back 7

The amount of material required for the bend must be determined to assure that the final dimensions will be correct. Bending a strip of metal compresses the material on the inside of the curve and stretches the material on the outside of the curve. However, in the approximate center between these two extremes is a space that is neither stretched nor compressed, which is called the neutral axis. When making a bend to exact dimensions, the length of the neutral line must be calculated so enough material can be allowed for the bend. Bend allowance depends on four factors: (1) the degree of bend, (2) the radius of the bend, (3) the thickness of the metal, and (4) the type of metal used. To save time in calculation of bend allowance, formulas, and charts for various angles, radii of bends, material thickness, and other factors have been established.

Front 8

What factors are used to determine setback?

Back 8

The radius of the bend and the thickness of the material; Setback = Radius + Thickness

Front 9

What is a joggle?

Back 9

A joggle is an offset formed on an angle strip to allow clearance for a sheet or extrusion.

Front 10

What are several methods used in forming sheet metal?

Back 10

Folding, bumping, crimping, shrinking, and stretching

Front 11

What may cause plastic to craze?

Back 11

Subjecting plastic to large stresses and exposure to harmful solvents will cause crazing.

Front 12

What rules apply for the replacement of 2017-T3 and 2024-T4 rivets with 2117-T3 rivets?

Back 12

You may replace 2017-T3 rivets of 3/16-inch diameter or less, and 2024-T4 rivets of 5/32 inch diameter or less with 2117-T3 for general repairs, provided the replacement rivets are 1/32 inch greater in diameter than the rivets they replace, and the edge distance and spacing are not less than specified minimums.

Front 13

Briefly describe the anodizing process and what purpose it serves.

Back 13

Aluminum alloys are placed in electrolytic bath which causes a thin film of hydroxide to form on the surface of the aluminum. This anodized coating not only provides excellent resistance to corrosion, but it is also an excellent bond for paint.

Front 14

What are the proper dimensions for a proper shop head?

Back 14

One and one/half times the diameter wide and one-half times the diameter thick after bucking

Front 15

When inspecting Plexiglas, what should you look for?

Back 15

Crazing and discoloration

Front 16

What causes honeycomb structure to delaminate?

Back 16

Moisture

Front 17

What are the acceptable repair methods for bonded honeycomb structure that has been damaged?

Back 17

There are two acceptable methods of repair currently being used on damaged skin and core materials of bonded honeycomb structures. One is the potted repair method. The other is the laminated glass fabric cloth overlay which is applied to honeycomb damage that exceeds the repair limitations of the potted compound method.

Front 18

What size drill should be used for the common shank rivet diameters of 3/32 inch, 4/32 inch, and 5/32 inch?

Back 18

For a 3/32 rivet, a number 40

For a 4/32 rivet, a number 30

For a 5/32 rivet, a number 21

Front 19

What is used for hole filling in a bonded honeycomb repair?

Back 19

Potting compound

Front 20

What is a lightning hole?

Back 20

Lightning holes are cut into rib sections, fuselage frames, and other structural parts to decrease weight. Flanges are pressed around the holes for strength.

Front 21

What is the approximate angle of the point of a center punch?

Back 21

60 degrees