Solid Rivets

Question 1

There are two common types of rivets that you will be using. What are the head styles and respective codes?

Answer 1

Universal and countersunk. AN/MS20470 and AN/MS20426

Question 2

The solid shank rivet code breakdown is one of the easier callouts. The callout consists of five parts. Example: MS20426AD5-8:

Answer 2

MS20 (Standard it is fabricated to, MS in this case being Mil standard or AN which is Army Navy)

426 (Head style, countersunk in this case)

AD (Alloying element, 2117T alloy in this case)

5 (Rivet diameter, 5/32nds in this case)

-8 (Length of the rivet, 8/16s or 1/2)

Question 3

When it comes to application, where are universal (470) and countersunk (426) are used?

Answer 3

Universals, being the most common, are used in areas where aerodynamic smoothness is not a factor. Countersunk rivets on the other hand, are used in areas where aerodynamic smoothness is an important factor, e.g. leading edges and forward sections of wings, horizontal stabs, etc.

Question 4

While the countersunk rivet gives us the required surface, it must be understood that a countersunk rivet does not have the Bearing Strength of a Universal head rivet because in most cases ___________________ for the countersunk head to seat in.

Answer 4

Material is milled away to form the nest or well for the fastener to set in.

Question 5

The aforementioned countersunk can be formed by cutting away the material with a microstop cut countersinker, or dimpling, using a male and female die to form the depression. Whichever way it is done, to mate with the AN426 rivet it must be a __________ degree countersunk. Why is this?

Answer 5

It must be a 100 degree countersunk. This degree gives the best bearing strength.

Question 6

A cut countersunk rivet may have a plus tolerance meaning that it may protrude from the surface approximately +_______”, but never cut so that the head is below the skin. On a dimpled skin, the countersink may be below the surface -____.” simply due to the nature of the process, or + _____”.

Answer 6

For cut countersunks, +.002 - .003”, Dimpled, -.004” or +.002

Question 7

The 2117 “AD” rivet is the most popular alloy rivet because it has __________, ___________, and also has a high
resistance to ________________. It is also referred to as the “field rivet” for what reasons?

Answer 7

Has excellent strength, shock resistance and high resistance to corrosion. It is also referred to as the field rivet as there is no need to heat treat it before driving it.

Question 8

The 2017 “D” rivet is used when more __________________________ using the same space. “D” rivets are referred to as “ICEBOX RIVETS” as they have to be _____________________ before use and then kept in a freezer so that they do not “Age Harden”

Answer 8

It is used when more strength is required than what the 2117 AD rivet provides. They are referred to as Icebox rivets as they need to be heat treated prior to being used to prevent age hardening.

Question 9

The “DD” rivet is another “ICEBOX RIVET” that is stronger again than the “D” rivet. This rivet must be heat-treated
(ANNEALED) before use just as the “D” rivet and kept in a freezer until use as well. The “DD” or 2024 rivet must be driven within ___________________ of removal from the freezer.

Answer 9

It must be driven within 10 to 20 minutes once removed from the freezer.

Question 10

Swelling in the rivet hole is important to achieve full strength. As the hole drilled will be .002” to “.004” larger than the rivet itself. What will happen if you use a rivet that is too short?

Answer 10

You will end up with a rivet that does not have enough material to fill the void in the hole.

Question 11

When determining the total length of a rivet for installation, the combined thickness of materials involved must be considered. What is this measurement known as?

Answer 11

Grip length.

Question 12

The total length of the rivet should be equal to the grip length plus the amount of rivet shank required to form the __________

Answer 12

Rivet shank needed to form the Shop head.

Question 13

The extra length of the shank needed to form the shop head is always ________

Answer 13

1.5 x the diameter

Question 14

What is the formula for determining the grip length and correct rivet size to go with it?

Answer 14

GL+(1.5xD)/.0625.

Question 15

Say you want to join two sheets of .032 aluminum using a -4 or 1/8th rivets, what would be the GL and the rivet shank length required?

Answer 15

0.032+0.032=0.064
1/8= 0.125

0.064 + (1.5x0.125)/0.0625 = 4.024 or simply -4

Question 16

If the shop head is formed properly, the height of the shop head will always be ______ of the original shank length.

Answer 16

Will be one half the original size.

Question 17

There are two primary stresses that act on a rivet. What are these forces?

Answer 17

Shear and tension.

Question 18

What is the difference between shear and tension stresses in aviation?

Answer 18

Shear is the force tending to cause one of the materials to slide on top over another. Tension is two or more pieces of material being pulled apart.

Question 19

What are the two strengths of a rivet that must be considered?

Answer 19

Bearing strength and shear strength.

Question 20

What is shear strength and bearing strength?

Answer 20

Shear strength is the ability of the rivet to withstand being cut in half.

Bearing strength amount of force needed to pull the rivet through the edge of the sheet or elongate the hole.

Question 21

When choosing a rivet, shear strength of the rivet must be equal to the bearing strength of the sheet metal as much as possible. However, the thicker the metal is, the higher the shearing strength gets. In this case, bearing strength should always be higher than the shear strength. Why is this?

Answer 21

So that the rivet fails first before the skin itself.

Question 22

Determining bearing and shear strengths is always found with the help of charts. Double shear is always found by ________________.

Answer 22

Found by multiplying the numbers in the chart by two.

Question 23

The rivet diameter to be used is always determined by a formula. The diameter is by multiplying the thickest sheet by ___

Answer 23

Multiplying the thickest sheet by three.

Question 24

For example, say we want to join two pieces of .040. What is the appropriate diameter to be used?

Answer 24

.040 x 3 would equal .120. The appropriate rivet we can use is a -4 rivet as the diameter is a 4/32 rivet or 1/8th which is equal to 0.125

Question 25

When it comes to rivet layout, what is edge distance and why is it important?

Answer 25

It is the distance between of the center of a rivet to the edge of a sheet. ED is important as too close to the edge puts it at risk to being pulled through under load.

Question 26

Edge distance is measured in diameters of a rivet. ED has a minimum of _D and a maximum of _D.

Answer 26

ED has a minimum 2D and a maximum of 4D.

Question 27

What would happen if the ED is less than 2D or more than 4D?

Answer 27

Less than 2D will result in improper bearing strength. More than 4D would cause unwanted gaps between sheets along the edge.

Question 28

If the sheet metal in question is countersunk, what is the edge distance adjusted to and why?

Answer 28

It is set to 2.5D to compensate for the loss of material and lower bearing strength.

Question 29

Regardless on how they are called out on the drawing, rivets will never be pitched or spaced closer than _D or spaced further than _D.

Answer 29

Never be pitched closer than 3D or spaced further than 12D.

Question 30

What will happen to the sheets if the rivets are pitched or spaced closer or further than 3D and 12D?

Answer 30

Closer than 3D and the sheet will tear along the rivet placements, Further than 12D and the sheets will buckle and bulge in between.

Question 31

Drawings may give you a specific number of diameters between rivets. E.g. rivet spacing is 5D and the diameter of the rivet being used is 1/8”. What is the correct spacing between the rivets?

Answer 31

It would be 5x0.125 which would equal 0.625.

Question 32

Sometimes, a drawing may call for 8 rivets equally spaced. How do you determine the correct spacing from here?

Answer 32

After marking out your EDs, measure the distance in between and divide it by 7. We divide it by 7 since a rivet gets placed in the first hole.

Question 33

Sometimes rivets are not only installed in one row. Sometimes two or more rows of rivets are required to achieve adequate strength. This is where gauge or transverse pitch play an important role. What are. What is the meaning of transverse or gauge?

Answer 33

Transverse or gauge is the distance between rows of rivets.

Question 34

This distance between these rows of rivets is at least _% of the rivet pitch. and should be _________.

Answer 34

75% of the rivet pitch and should be staggered.

Question 35

What are the two primary methods of countersinking skin?

Answer 35

Cut-countersinking and dimpling.

Question 36

When cut-countersinking, why should you be careful to how, much material is left at the bottom of the nest?

Answer 36

If you cut too deep, this will result in a knife edge which will impair the strength.

Question 37

When cut-countersinking, why must you back your sheet up with another sheet of metal?

Answer 37

Backing it up will stabilize the pilot and eliminate any chances of it spinning violently and ruining the hole.

Question 38

Remember that its okay to be proud by at least .003’ but never below the surface. If it is over that specific tolerance, you may shave it. How much can the total head diameter of a countersunk rivet be shaved to?

Answer 38

It may be shaved to a maximum 5% of the original head diameter.

Question 39

Dimpling is when the material surrounding the hole is forced into the proper shape to suite the countersunk rivet. When is this is process used instead of cut-countersinking?

Answer 39

When the material is less than .040

Question 40

What is the difference between coin and radius dimpling and what is the advantage of coin dimpling?

Answer 40

Radius dimpling involves a female and male die with no moving parts. This process does not leave a well defined line around the hole. Coin dimpling on the other hand features a complex dies which makes the metal flow into the proper shape, resulting in a uniform finish.

Question 41

When drilling the holes into a sheet of metal that is to be dimpled, why should you use the fractional equivalent instead of the #drill?

Answer 41

Because once you dimple the hole, the process will expand the hole to the correct size for the rivet.

Question 42

When it comes to holding devices, we will use clecoes (pins used exclusively in the industry), clamps (manual or spring-loaded), and screws, bolts, and nuts. When do we use screws, nuts and bolts and what should you use to prevent the surface from being damaged?

Answer 42

When there is a large stack-up of material that would require a long holding device. Make sure you use washers beneath the heads of screws or bolts to prevent potential damage.

Question 43

Clecoes come in 4 main types of colors, silver, copper, black and brass. These colors correspond to their hole size. What are their sizes?

Answer 43

Silver: 3/32 or 0.09375
Copper: 1/8 or 0.125
Black: 5/32 or 0.156
Brass: 3/16 or 0.1875

Question 44

When removing rivets. what should we avoid?

Answer 44

Make sure you don’t oversize the hole.

Question 45

A solid shank rivet can achieve only _% of the sheet strength if it is properly installed.

Answer 45

Only 75% of the sheet strength.