Rivets
1. Brief Description :

A rivet is a permanent mechanical fastener. Before being installed, a rivet consists of a smooth cylindrical shaft with a head on one end. The end opposite to the head is called the tail. On installation, the rivet is placed in a punched or drilled hole, and the tail is upset, or bucked (i.e., deformed), so that it expands to about 1.5 times the original shaft diameter, holding the rivet in place. In other words, pounding creates a new "head" on the other end by smashing the "tail" material flatter, resulting in a rivet that is roughly a dumbbell shape. To distinguish between the two ends of the rivet, the original head is called the factory head and the deformed end is called the shop head.

Because there is effectively a head on each end of an installed rivet, it can support tension loads. However, it is much more capable of supporting shear loads (loads perpendicular to the axis of the shaft).

Fig. 1: Snap Head Rivet
Fig. 2: Countersunk Rivet
Video of Pneumatic Rivetting
2. Defects in Rivets :
Fig. 3: Defects in Rivets
3. Procedure for checking the loose rivets :

Detailed procedure has given in Annexure 11/12 of IRBM.

Tap smartly on Dolly side by rivet testing hammer. Rivet testing hammer is 310mm long & weight is 110 gm.
Finger on other side shall not feel the vibrations.

Sample rivets to be tested in each category. After rivet testing, the heads of tested rivets shall be marked/painted.

Fig. 4: Rivet Testing

Three categories of Rivets are :

(a) Stitch rivets to ensure joint action of the various components of a member - Do not get loose.

(b) Rivets to join/splice members - Critical rivets, to be closely watched out for.

(c) Rivets in Bracing - Most likely to be found loose, but these are non-critical rivets as these do not transfer the main load on the girder.

4. Loose Rivets Replacement :

Slightly loose rivets which can be felt only by hammer do not lose their load carrying capacity and need not be disturbed unless these are in critical locations and are In groups Having corrosion Hand loose or finger loose rivets lose load carrying capacity and have to be replaced.