Special microstop countersinks (commonly called stop countersinks) are available that can be adjusted to any desired depth and have cutters to allow interchangeable holes with various countersunk angles to be made. The standard countersink has a 100º angle, as shown in Figure 3. Countersinks are made with angles to correspond with the various angles of countersunk rivet heads. The header part consists of a hole shallow enough for the set to expand the rivet and head when struck with a hammer.Ĭountersinking ToolThe countersink is a tool that cuts a cone-shaped depression around the rivet hole to allow the rivet to set flush with the surface of the skin. Occasionally, the draw set and rivet header are incorporated into one tool. Each draw set has a hole 1⁄32-inch larger than the diameter of the rivet shank for which it is made. Special draw sets are used to draw up the sheets to eliminate any opening between them before the rivet is bucked. To seat flush rivets properly, be sure that the flush sets are at least 1 inch in diameter. Flush or flat sets are used for countersunk and flathead rivets. In selecting the correct set, be sure it provides the proper clearance between the set and the sides of the rivet head and between the surfaces of the metal and the set. Sets for universal rivets are recessed (or cupped) to fit the rivet head. Only the face of the set is hardened and polished. The ordinary set is made of 1⁄2-inch carbon tool steel about 6 inches in length and is knurled to prevent slipping in the hand. Rivet sets are available to fit every size and shape of rivet head. Hand Rivet SetA hand rivet set is a tool equipped with a die for driving a particular type rivet. Their edges should be slightly rounded to prevent marring the material surrounding the riveting operation. The bars must be kept clean, smooth, and well polished. With experience, a high degree of skill can be developed.ĭefective rivet heads can be caused by lack of proper vibrating action, the use of a bucking bar that is too light or too heavy, and failure to hold the bucking bar at right angles to the rivet. Coordinated bucking allows the bucking bar to vibrate in unison with the gun set. The operator’s hands merely guide the bar and supply the necessary tension and rebound action. Allow the weight of the bucking bar to do most of the work and do not bear down too heavily on the shank of the rivet. If the bucking bar is removed while the gun is in operation, the rivet set may be driven through the material. The bucker must hold the bucking bar in place until the rivet is completely driven. Failure to do so causes the rivet shank to bend with the first blows of the rivet gun and causes the material to become marred with the final blows. Always hold the face of the bucking bar at right angles to the rivet shank. This tool is used by holding it against the shank end of a rivet while the shop head is being formed.
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