Maximum pitch shall not exceed 32 times the thickness of the thinner outside plate or 300 mm whichever is less. As a thumb rule pitch equal to 3 times the nominal diameter of the rivet is adopted. Minimum pitch should not be less than 2.5 times the nominal diameter of the rivet. The pitch of rivet is the distance between two consecutive rivets measured parallel to the direction of the force in the structural member, lying on the same rivet line. ![]() Strengths of rivet are based on gross diameter. The gross or effective diameter of a rivet means the diameter of the hole or closed rivet. As the rivet is heated and driven, the rivet fills the hole fully. The diameter of the hole is slightly greater than the diameter of the rivet shank. The nominal diameter of a rivet means the diameter of the cold shank before driving. ![]() The diameter of a rivet hole is made larger than the nominal diameter of the rivet by 1.5 mm of rivets less than or equal to 25 mm diameter and by 2 mm for diameter exceeding 25 mm.ĥ.5 DEFINITIONS OF TERMS USED IN RIVETING When the hole are made by drilling, the holes are perfect and provide good alignment for driving the rivets. The operation known as reaming is done in the hole made by punching. A punch damages the material around the hole. When the holes are made by punching, the holes are not perfect, but taper. The rivet holes are made in the plates or structural members by punching or drilling. When a smooth flat surface is required, it is necessary to have rivets countersunk and chipped. A rivet head which has the form of a truncated cone is called a countersunk head. Sometimes it becomes necessary to flatten the rivet heads so as to provide sufficient clearance. The snap heads are used for rivets connecting structural members. The snap head is also termed as round head and button head. The proportions of various shapes of rivet heads have been expressed in terms of diameter ‘D’ of the shank of rivet. The various types of rivet heads employed for different works are shown in Fig. Where d= nominal diameter of rivet in mm and t= thickness of plate in mm. The diameter of rivet to suit the thickness of plate may be determined from the following formulae: The use of cold driven rivets is limited because of equipment necessary and inconvenience caused in the field. The strength of rivet increases in the cold driving. The small size rivets ranging from 12 mm to 22 mm in diameter may be cold driven rivets. The cold driven rivets need larger pressure to form the head and complete the driving. These rivets are known as cold driven rivets. Some rivets are driven at atmospheric temperature. The hot driven rivets of 16 mm, 18 mm, 20 mm and 22 mm diameter are used for the structural steel works. These rivets are known as hot driven rivets. When the hot rivet so fitted cools it shrinks and presses the plates together. Keeping the rivets pressed from one side, a number of blows are applied and a head at the other end is formed. For driving the rivets, they are heated till they become red hot and are then placed in the hole. Holes are drilled in the plates to be connected at the appropriate places. ![]() The size of rivet is expressed by the diameter of the shank. The rivets are manufactured in different lengths to suit different purposes. The head of rivet is formed by heating the rivet rod and upsetting one end of the rod by running it into the rivet machine. A rivet consists of a head and a body as shown in Fig 5.1. Rivets are made from mild steel bars with yield strength ranges from 220 N/mm 2 to 250 N/mm 2. Rivet is a round rod which holds two metal pieces together permanently. Rivets and welds are used as permanent fastenings i.e., the components connected are not likely to require separation. Of these screws, pins, bolts, cotters and gibs are used as temporary fastening i.e., the components connected can be separated easily. The following are the usual applications for connection. Such joints have been used in structures, boilers and ships. If force at each of the free edges is applied for pulling the plate apart the tensile stress in the plate along the row of rivet hole and shearing stress in rivets will create resisting force. With such a joint having been created between two plates, they cannot be pulled apart. A number of rivets may pass through the row of holes, which are uniformly distributed along the edges of the plate. A riveted joint is easily conceived between two plates overlapping at edges, making holes through thickness of both, passing the stem of rivet through holes and creating the head at the end of the stem on the other side. Many times such joints are required to be leak proof so that gas contained inside is not allowed to escape. In engineering practice it is often required that two sheets or plates are joined together and carry the load in such ways that the joint is loaded.
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