Drilling Rivet HolesStandard twist drills are used to drill rivet holes.Table 13-2 specifies the size drill to be used with thevarious size rivets.Note that there is a slightclearance in each case. This prevents binding of therivet in the hole.Locations for the rivet holes should be centerpunched and the drilling done with a power drill,either electric or pneumatic. Electric drills constitutea fire hazard when you are drilling on or near anaircraft. The hazard is caused by the arcing of thebrushes. Therefore, the pneumatic drill should beused. The center punch mark should be large enoughto prevent the drill from slipping out of position, butmust not be made with enough force to dent thesurrounding material. All burrs must be removed byusing a larger size drill or by using a deburring tool.Flush RivetingIn aircraft construction, manufacturers areeliminating protruding-head rivets on the exteriorsurfaces.In fabricating stressed metal skin, allexposed rivet heads must be countersunk to lie flushwith the outer surface of the skin. It is essential toprovide an aerodynamically smooth surface. Seefigure 13-45.Flush rivets are more difficult to install becausethe parts being riveted must be countersunk. Anotherhazard is the closeness of the rivet set to the metalduring riveting. If considerable skill is not used, themetal will be damaged by the rivet set. Flush rivetsare made with heads of several different angles, butthe 100-degree rivet is standard for all Navy aircraft.The two methods used to countersink flush rivetsare dimple and machine countersinking. In someinstances, a combination of the two may be used; inother words, the top sheet of an assembly may bedimpled while the under sheet is machinecountersunk.Rivet DrivingBefore driving any rivets, make sure all the holesline up perfectly, all the shavings and burrs have beenremoved, and the parts to be riveted are fastenedsecurely together. It is important that the sheets beheld firmly together near the area of the rivet beingdriven.Table 13-2.—Drill Sizes for Various Size RivetsTo adjust the speed of the gun, place it against ablock of wood. Never operate a rivet gun withoutresistance against the set. The vibrating action maycause the retaining spring to break, allowing the set tofly out.WARNINGA rivet set can be a deadly weapon. If arivet set is placed in a rivet gun without aset retainer and the throttle of the gun isopened, the rivet set may be projected likea bullet. This may cause severe injury to aperson or destruction of equipment.Figure 13-45.—Incorrect countersinking.13-28
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