Cut the material to size, allowing about 1⁄4-inch excess material for trim and drill holes for alignment pins. A power slip roller is often used if the repair patch needs to be curved to fit the contour of the aircraft. Space the additional crimps between the original ones so that the metal does not become unduly work hardened at any one point. Insert the sheet in the brake and bend the metal up approximately 20° to 30°. The pilot guide should be the same size as the hole to be flanged, and the shoulder should be the same width and angle as the desired flange. An overly heavy blow buckles the metal, so keep moving the flange across the V-block, but always lightly strike the spot directly above the V. Lay out a full-sized, accurate pattern on a sheet of paper or plywood and periodically check the accuracy of the curve. Bandsaws should be equipped with nonsparking blade guides to eliminate the danger of sparks igniting the magnesium alloy filings. Using a plastic or rawhide mallet with a smooth, slightly rounded face, start hammering at the extreme ends of the part and continue toward the center of the bend. Whenever such machines are not available, comparatively short sections can be bent by hand with the aid of wooden or metal bending blocks. When working with stainless steel, make sure that the metal does not become unduly scratched or marred. When working titanium, it is recommended that you use carbide or 8 percent cobalt drill bits, reamers, and countersinks. Spring-back is reduced, resulting in greater dimensional accuracy. Inconel® refers to a family of nickel-chromium-iron super alloys typically used in high-temperature applications. This induces a setting process in the bend. For hard metal or for more permanent use, they should be made of steel. The degree of shifting depends largely on the contour or shape of the piece being formed, and whether glancing blows must be struck to stretch, draw, or shrink the metal. If any part of the angle strip is curved too much, reduce the curve by reversing the angle strip on the V-block, placing the bottom flange up, and striking it with light blows of the mallet. If the form blocks are made of hardwood, use a metal planishing hammer. In some cases, the part may have to be annealed during the curving operation. Roll forming may be accomplished cold on equipment designed for forming aluminum. After the form is prepared and checked, perform the bumping as follows: Cut a metal blank to size allowing an extra 1⁄2 to 1-inch to permit drawing. The forming of titanium alloys is divided into three classes: Elevated temperature forming (built-in stress relief). Curved flanged parts are usually hand formed with a concave flange, the inside edge, and a convex flange, the outside edge. To form the joggle, use the following procedure: Lay out the boundary lines of the joggle where the bends are to occur on the sheet. Inconel® alloys 625 and 718 can be cold formed by standard procedures used for steel and stainless steel. CRES causes magnesium, aluminum, or cadmium to corrode when it touches these metals. For flanging soft metal, dies can be of hardwood, such as maple. In this process, crimp the flange that is to form the inside of the curve. Use of the joggle maintains the smooth surface of a joint or splice. For blanking, the shear angle on the die should be from 2° to 3° with a 1° clearance angle on the punch. Too much clearance permits the metal to be drawn over the edge of the die and causes it to become work hardened, resulting in excessive strain on the machine. The flange and the beaded (raised ridge on sheet metal used to stiffen the piece) portion of this rib provide sufficient strength to make this a good type to use. The following are procedures for cold forming titanium 6Al-4V annealed with stress relief (room temperature forming): It is important to use a minimum radius chart when forming titanium because an excessively small radius introduces excess stress to the bend area. Complete the crimp by working a raised portion into the flange, gradually increasing the twisting motion of the pliers. A joggle, often found at the intersection of stringers and formers, is the offset formed on a part to allow clearance for a sheet or another mating part. For example, if a formed or extruded angle is to be curved, either stretch one leg or shrink the other, whichever makes the part fit. Apply the powder on the burning metal to a depth of 1⁄2-inch or more. When hand drilling thin or flexible parts, put a support (such as a block of wood) behind the part. Corrosion resistance and the ability to stay strong in high temperatures led to the frequent use of these Inconel® alloys in aircraft powerplant structures. Drill the material on a backing plate, such as cast iron, which is hard enough to permit the drill bit to cut completely through the stock without pushing the metal away from the drill point. After the joggle is formed, the joggle blocks are turned over in the vice and the bulge on the opposite flange is flattened with a wooden or rawhide mallet. If a large amount of metal extends beyond the forming blocks, maintain hand pressure against the protruding sheet to prevent it from bouncing. Small and medium extrusions are more easily cut on a circular cutoff saw having six teeth per inch. Continue bumping toward the center, revolving the metal, and working gradually inward until the desired shape is obtained. Bend the flange on the concave curve first. When alloyed with these other metals, magnesium, yields alloys with excellent properties and high strengthto-weight ratios.

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