Rivets for aircraft and aerospace fasteners
aircraft rivets
The two main types of rivets used on aircraft are common solid shank rivets, which must be driven with an air-powered gun and bucking bar; and special (blind) rivets, which are installed with special installation tools. Solid shank rivets are widely used during assembly and repair work. They are identified by the material from which they are made, the type of head, the size of the shank and the state of temper.
The material used for most solid shank rivets is aluminum alloy. Strength and temper conditions of aluminum alloy rivets are identified by digits and letters similar to those used to identify sheets. Rivets 1100, 2017-T, 2024-T, 2117-T and 5056 are the six grades normally available. Type AN aircraft solid rivets can be identified by code markings on the rivet heads. A rivet made from 1100 material is designated an “A” rivet and has no marking on the head. The 2017-T alloy rivet is designated a “D” rivet and has a raised nipple on the head. Two dashes on a head indicate a 2024-T alloy designated as a “DD” rivet. The 2117-T rivet is designated the “AD” rivet and has a dimple in the head.
A “B” designation is given to a 5056 material rivet and is marked with a raised cross on the head. Each type of rivet is identified by a part number so the user can select the correct rivet. The numbers are in series and each series represents a particular type of head.
Countersunk head rivets are used when a smooth finish is desired. The 100 degree countersunk head has been adopted as the standard in the United States. Universal head rivet (AN470) has been adopted as the standard for protruding head rivets and can be used as a replacement for round head, flat head and brazier head rivet. These rivets can also be purchased in half sizes by designating a “0.5” after the main length.
Replace rivets with ones of the same size and strength whenever possible. If the rivet hole is enlarged, deformed or damaged; Drill or ream the hole for the next larger size rivet. Rivets cannot be replaced by a type that has lower strength properties unless the lower strength is adequately compensated for by an increase in size or increased number of rivets. It is acceptable to replace 2017 rivets 3/16″ in diameter or less, and 2024 rivets 5/32″ in diameter or less with 2117 rivets for general repairs, provided the replacement rivets are 1/32″ in diameter. greater than the rivets they replace
Rivet edge distance is defined as the distance from the center of the hole to the nearest edge of the sheet. Rivet spacing is the distance from the center of the rivet hole to the center of the adjacent hole. Unless structural deficiencies are suspected, spacing and edge distance should duplicate that of the original aircraft structure. If structural deficiencies are suspected, the following can be used to determine the minimum edge distance and spacing between rivets. Special fasteners may require FAA field approval.
Blind rivets are used in certain conditions when only one side of the structure is accessed. In general, the locking characteristics of a blind rivet are not as good as those of a driven rivet. Therefore, blind rivets are generally not used when driven rivets can be installed.
2117 rivets can be set as received, but 2017 rivets over 3/16 inch in diameter and all 2024 rivets should be kept packed on dry ice or refrigerated in “off” conditions until set or stored. heat treat again. before nailing, as they would otherwise be too hard for satisfactory riveting.
Aerospace fixings, special fixings and blind fixings.
When solid shank rivets are not practical, special fasteners are used. Specialty fastening systems used for aircraft construction and repair are divided into two types, special and blind fasteners. Special fasteners are sometimes designed for a specific purpose in an aircraft structure. The name “special fasteners” refers to their job requirement and the tools needed for installation. They are used in fluid-tight areas, on aircraft in the air intake where the engine can ingest rivet parts, on aircraft control surfaces, hinges, hinge brackets, overstage flight control system, fixtures wings, landing gear fittings, on amphibian floats or hulls below water level, or other highly stressed locations on the aircraft. For airframe metal repairs, the use of pop rivets must be specifically authorized by the airframe manufacturer or approved by an FAA representative.
Self-locking cherry rivets with friction lock. This patented rivet can be installed when accessing only one side of the structure. The blind head is formed by pulling the tapered stem into the hollow stem. This swells the leg and holds the skins tightly. When the stem is completely altered, the stem splits in two. The shank does not fracture flush with the head and must be trimmed and filed flush to complete the installation. Due to the friction locking stem, these rivets are very sensitive to vibrations. Inspection is visual, with a loose rivet sticking out in the standard “smoking rivet” pattern. Removal involves drilling through the friction-locked stem and then treating it like any other rivet. Mechanical locking rivets have a device on the extractor or head that locks the center pin in place when installed. Many center shanks of friction lock rivets fall out due to vibration; this, in turn, greatly reduces its shear strength. The mechanical locking rivet was developed to avoid this problem. Various manufacturers make mechanical locking fasteners such as: Bulbed Cherrylock, CherryMax, Olympic-Loks, and Huck-Loks.