The rivet codes shown in figure 2-1 are sufficient to identify rivets only by head shape. To be meaningful and precisely identify a rivet, certain other information is encoded and added to the basic code.

Figure 2-1.Rivet head shapes and code numbers.

A letter or letters following the head-shaped code identify the material or alloy from which the rivet was made. Table 2-1 includes a listing of the most common of these codes. The alloy code is followed by two numbers separated by a dash. The first number is the numerator of a fraction, which specifies the shank diameter in thirty-seconds of an inch. The second number is the numerator of a fraction in sixteenths of an inch, and identifies the length of the rivet. The rivet code is shown in figure 2-2.

Rivet Composition 

Most of the rivets used in aircraft construction are made of aluminum alloy. A few special-purpose rivets are made of mild steel, Monel, titanium, and copper. Those aluminum alloy rivets made of 1100, 2117, 2017,2024, and 5056 are considered standard.

ALLOY 1100 RIVETS. Alloy 1100 rivets are supplied as fabricated (F) temper, and are driven in this condition. No further treatment of the rivet is required before use, and the rivets properties do not change with prolonged periods of storage. They are relatively soft and easy to drive. The cold work resulting from driving increases their strength slightly. The 1100-F rivets are used only for riveting nonstructural parts. These rivets are identified by their plain head, as shown in table 2-1.

ALLOY 2117 RIVETS. Like the 1100-F rivets, these rivets need no further treatment before use and can be stored indefinitely. They are furnished in the solution-heat-treated (T4) temper, but change to the

solution-heat-treated and cold-worked (T3) temper after driving. The 2117-T4 rivet is in general use throughout aircraft structures, and is by far the most widely used rivet, especially in repair work. In most cases the 2117-T4 rivet may be substituted for 2017-T4 and 2024-T4 rivets for repair work by using a rivet with the next larger diameter. This is desirable since both the 2017-T4 and 2024-T4 rivets must be heat treated before they are used or kept in cold storage. The 2117-T4 rivets are identified by a dimple in the head.