jaws of the C-clamps should be covered with masking tape.  If the angle has already closed, bring the flange back to the  correct angle with a few blows of a mallet or with the aid  of a small hardwood block. If any portion of the angle strip  is curved too much, reduce it by reversing the angle on the  V-block and hammering with a suitable mallet, as explained  in the previous paragraph on stretching. After obtaining the  proper curve, smooth the entire angle by planishing with a  soft-faced mallet. 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. In this process, crimp the flange  that is to form the inside of the curve. When making a crimp, hold the crimping pliers so that the  jaws are about  1 ⁄ 8-inch apart. By rotating the wrist back and  forth, bring the upper jaw of the pliers into contact with the  flange, first on one side and then on the other side of the  lower jaw. Complete the crimp by working a raised portion  into the flange, gradually increasing the twisting motion of  the pliers. Do not make the crimp too large because it will  be difficult to work out. The size of the crimp depends upon  the thickness and softness of the material, but usually about  1 ⁄ 4-inch is sufficient. Place several crimps spaced evenly along  the desired curve with enough space left between each crimp  so that jaws of the shrinking block can easily be attached. After completing the crimping, place the crimped flange in  the shrinking block so that one crimp at a time is located  between the jaws.  [Figure 4-150]  Flatten each crimp with  light blows of a soft-faced mallet, starting at the apex (the  closed end) of the crimp and gradually working toward the  edge of the flange. Check the curve of the angle with the  pattern periodically during the forming process and again  after all the crimps have been worked out. If it is necessary to  increase the curve, add more crimps and repeat the process.  Space the additional crimps between the original ones so that  the metal does not become unduly work hardened at any one  point. If the curve needs to be increased or decreased slightly  at any point, use the V-block. After obtaining the desired curve, planish the angle strip over  a stake or a wooden form. The forming process for the following two flanged angles  is slightly more complicated than the previously discussed  angles because the bend is shorter (not gradually curved) and  necessitates shrinking or stretching in a small or concentrated  area. If the flange is to point toward the inside of the bend, the  material must be shrunk. If it is to point toward the outside,  it must be stretched.  In forming a flanged angle by shrinking, use wooden forming  blocks similar to those shown in  Figure 4-151  and proceed  as follows: 1.  Cut the metal to size, allowing for trimming after  forming. Determine the bend allowance for a 90° bend  and round the edge of the forming block accordingly. 2.  Clamp the material in the form blocks as shown in  Figure 4-151,  and bend the exposed flange against  the block. After bending, tap the blocks slightly. This  induces a setting process in the bend. Shrinking Flanged Angles Figure 4-151.  Forming a flanged angle using forming blocks. Figure 4-150.  Crimping a metal flange in order to form a curve.  4-76 Form blocks Hardwood wedge block