After completing the crimping, place the crimped flange in the shrinking block so that one crimp at a time is located between the jaws. It is important to use a bend radius that is larger than the recommended minimum bend radius to prevent cracking of the material in the bend area. When it becomes hot, other metals become easily attached to it. Determine the bend allowance for a 90° bend and round the edge of the forming block accordingly. Work the material down gradually from the edges with light blows of the mallet. [Figure 14] In this method, a depression is made into the sandbag to take the shape of the hammered portion of the metal. Holes with a diameter of 0.1875-inch and larger can be hand drilled if the operator: - Starts with a hole with a diameter of 0.1563-inch. Clamp the material between the block and steel plate. Prepare several templates (patterns of the crosssection), as shown in Figure 13 so that the form can be checked for accuracy. Continue this process until the protruding metal is bent to the desired angle against the forming block. Sandbag bumping is one of the most difficult methods of hand forming sheet metal because there is no exact forming block to guide the operation. CRES causes magnesium, aluminum, or cadmium to corrode when it touches these metals. Commercially pure titanium sheet may be formed by hydropress, stretch press, brake roll forming, drop hammer, or other similar operations. Magnesium alloys must not touch methyl alcohol. It is light weight, nonmagnetic, strong, corrosion resistant, and ductile. [Figure 11]. NOTE: The intimate metal-to-metal contact in the metal working process creates heat and friction that must be reduced or the tools and the sheet metal used in the process are quickly damaged and/or destroyed. Conventional shears and nibblers should never be used for cutting magnesium alloy sheet because they produce a rough, cracked edge. ABN Sheet Metal Hand Seamer - 3 Inch Straight Jaw Manual Metal Bender Tool Sheet Metal Bending Pliers Flattening Tool. If the curve in a formed angle is to be quite sharp or if the flanges of the angle are rather broad, the shrinking block method is generally used. Titanium can be difficult to drill, but standard high-speed drill bits may be used if the bits are sharp, if sufficient force is applied, and if a low-speed drill motor is used. When heating magnesium and its alloys, watch the temperature carefully as the metal is easily burned. If water touches molten magnesium, a steam explosion could occur. The following paragraphs discuss some of these techniques. Light weight is the best known characteristic of magnesium, an important factor in aircraft design. Shearing and blanking of magnesium alloys require close tool tolerances. Hold one edge of the metal in the left hand and place the portion to be bumped near the edge of the pit on the sandbag. The machining characteristics of magnesium alloys are excellent, making possible the use of maximum speeds of the machine tools with heavy cuts and high feed rates. This requires preheating of the metal or dies, or both. Over 5 percent of all titanium in the United States is produced in the form of the alloy Ti 6Al-4V, which is known as the workhorse of the titanium industry. Keep a uniform pressure on the drill so the feed is constant at all times. Clamp the bumping block in a bench vise. If so, be sure to heat treat the part again before installing it on the aircraft. Remove the blister from the bumping block and trim to size. Lay out and cut the contour template to serve as a working guide and to ensure accuracy of the finished part. These dies are sufficiently soft and resilient to permit forming aluminum alloy parts on them without marring, and nicks and scratches are easily removed from their surfaces. It should also be curved slightly beyond 90° to allow for spring-back. Using the process outlined in the stretching paragraphs, begin at one end of the angle strip and work back and forth making light blows. In either case, the metal is ruined. Sheet stock can be cut on handsaws having raker-set or straight-set teeth with an 8-tooth pitch. The edges are filed smooth to prevent them from cracking or tearing. Filings, shavings, and chips from machining operations should be kept in covered metal containers because of the danger of combustion. Titanium must be isolated from magnesium, aluminum, or alloy steel because galvanic corrosion or oxidation of the other metals occurs upon contact. The forming of titanium alloys is divided into three classes: Elevated temperature forming (built-in stress relief). Several methods of stretching and shrinking may be used, depending on the size, shape, and contour of the part being formed. Ensure it is firmly supported yet it can slip a little toward the inside of the form. Particles of titanium often become welded to the sharp edges of the drill bit if the drill speed is too high. Annealed sheet may be heated to 600 °F, but hardrolled sheet must be held under 400 °F, depending on the alloy used. There are problems in lubricating and handling materials at these temperatures. To prevent burning, magnesium must be protected with a sulfur dioxide atmosphere while being heated.