RIVET IDENTIFICATION

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The majority of aircraft rivets are manufactured from aluminium alloys. Rivets can also be made from other materials such as steel, Monel metal, titanium or copper.

Material specifications for British and American rivets are not identical. The manufacturer’s publications (AMM or CMM) will give details on which rivets can be used if the specified ones are unavailable.

The dimensions that identify the size of a rivet are simply its length and diameter.

Other identifying features are the shape of the head, (including the countersink angle, if applicable) and the material from which the rivet is made. This latter requirement involves many different identifying marks and letters.

13.2 RIVET IDENTIFICATION

The identification of solid rivets covers a multitude of marks and letters that indicate, not only the material, but also the heat treatment, (if any), that the rivet has gone through.

The American rivets are, usually, ‘natural’ (gold) or grey in colour and have head markings, whilst British rivets, generally, use a combination of colour and alpha/numeric codes.

13.2.1 SOLID RIVETS (BRITISH)

Standards for British Solid rivets are issued by the Society of British Aerospace SBAC (AS series) or the British Standards Institute (SP series). The standards overlap to a certain extent, with obsolete rivets, in the AS range, being replaced by SP rivets.

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13.2.2 RIVET IDENTIFICATION (BRITISH)

A standard number and a part number are used to identify rivets. The standard number identifies the head shape, material and finish. This is followed by a three or four figure code, the first one or two figures indicating the shank diameter in thirty-seconds of an inch and the last two, the length in sixteenths of an inch.

Example:

A British rivet, with the identifying code AS 162-408, would be a 90° countersunk, aluminium alloy (5% magnesium) rivet, of 1/8 inch diameter and 1/2 inch long.

The AS 162 indicates the head type and material, while the ‘-4’ indicates that it has a 4/32 inch (1/8 inch) diameter and ‘08’ indicates it has a length of 8/16 inch (1/2 inch).

13.2.3 RIVET MATERIAL IDENTIFICATION (BRITISH)

Tables 13 and 14 give details on materials and identification marks for the various types of AS rivets. Many of these rivets are obsolescent and have been

superseded by rivets conforming to SP standards.

Table 15 gives details of material and identification information for SP rivets with the standard numbers shown in Table 16. SP rivets are also available in metric sizes.

Note: The colour coding (of both British systems) of solid rivets is generally the same as that used for the similar material in the other system. For example (in both systems) pure aluminium rivets are black, Hidiminium rivets are violet, Monel rivets are natural and 5% magnesium rivets are green. This way of coding allows material types to be more easily identified.

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MATERIAL IDENTIFICATION OF AS RIVETS Matl. Spec. Material Type Identification Marks Finish

L37 Dural ‘D’ on shank end Natural

TYPICAL SPECIFICATION NUMBERS OF AS RIVETS Material

MATERIAL IDENTIFICATION OF SP RIVETS Material.

Spec.

Material Type Identification Marks (On shank end)

TYPICAL SPECIFICATION NUMBERS OF SP RIVETS

Material Spec. Snap Head Mushroom Head 100º Csk Head

L36 SP77 - SP68

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13.2.4 SOLID RIVETS (AMERICAN)

These are generally used in normal construction and repair work. They are identified by the kind of material from which they are made, their head type, shank size and temper condition. Typical head types (refer to Fig. 72) are Roundhead, Brazier head, 100º Countersunk head, Flat head and Universal head.

AN Rivet Head Types

AN Material Identification and Code Letters Fig. 72

Raised Dot 2 Raised Dashes

Dimple

Plain Cross

A AD D DD B

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13.2.5 RIVET IDENTIFICATION (AMERICAN)

The rivets, shown in Fig. 72, are of the AN (Air Force-Navy) designation and are merely used to illustrate a typical coding system. The other most common

standard for American rivets is the MS (Military Standards) system which, whilst having slight differences from the AN system, uses similar terminology to

describe the many forms of rivets.

A part number (using the standard letters AN or MS) identifies each type of rivet, so that the user can select the correct rivet for the task. After the standard letters, there follows a number, which indicates the particular type of rivet head,

Next comes a letter (or letters), denoting the material composition, which is followed by another figure expressing the diameter of the rivet shank in 32ndsof an inch. The last number(s), separated by a dash from the diameter number, express the length of the rivet shank in 16ths of an inch.

Example:

An American AN system rivet with the identifying code AN470 AD 3-5, would be a Universal head, aluminium alloy (2117-T) rivet, of 3/32 inch diameter with a shank length of 5/16 inch.

Note: With countersunk rivets, the length is the overall length.

Head markings, using dimples and raised dots (or dashes and rings) are also used as an aid to indicate the material content of the rivets.

Protective surface coatings, used by the manufacturers, are shown by colours, where zinc chromate is usually yellow, an anodised rivet is usually pearl grey and a metal sprayed rivet has a silvery grey colour.

13.2.6 RIVET MATERIAL IDENTIFICATION (AMERICAN)

As previously stated, the material used for the majority of aircraft solid rivets is aluminium alloy. Digits and letters identify the degree of temper condition, of aluminium alloy rivets, in a similar manner to that used for sheet aluminium alloy.

The normal material grades are 1100, 2017-T, 2024-T, 2117-T and 5056.

The 1100 (A) rivet is 99.45% pure aluminium and, as such, is very soft. It would be used for riveting lightweight, soft, aluminium structures, where strength is not a factor.

The 2117-T (AD) rivet is made from aluminium alloy and (as has previously been mentioned) is known as the ‘field’ rivet. It is the most commonly used rivet, mainly because it is ready to use as received and needs no further heat-treatment. It also has a high resistance to corrosion.

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The 2017-T (D) and 2024-T (DD) rivets are made from high strength heat- treatable aluminium alloys. They are used where more strength is required than that obtained from the ‘field’ rivet. The rivets need to be heat-treated and, if not required immediately, they should be refrigerated until needed. The 2017-T rivet should be driven within 1 hour of removal from refrigeration (or following heat-treatment) and the 2024-T must be driven within 10-20 minutes.

The 5056 (B) rivet is used for riveting magnesium alloy structures, because of its galvanic compatibility with magnesium (to reduce the risk of corrosion).

Mild Steel rivets are used for riveting steel parts while Corrosion Resistant Steel rivets are used for riveting CRS components in fire-walls and exhaust areas etc.

Note: The absence of a letter following the AN standard number indicates a rivet manufactured from mild steel.

Monel (M) rivets are used for riveting nickel-steel alloys. They may also be used as a substitute for CRS rivets when specified.

Copper (C) rivets are also available, but their use is limited on aircraft. They may only be used on copper alloys or non-metallic materials, such as leather.

Note: Most metals, including aircraft rivets, are subject to corrosion. This may be the result of local climatic conditions or the fabrication process used. It can be reduced to a minimum by using the correct materials and by the use of protective coatings on the structure and the rivets. The use of dissimilar metals should be avoided where possible and, as previously stated, the rivet manufacturers usually apply a protective coating on the rivets, which may be either of a zinc chromate, a metal spray or an anodic film finish.