3.  Using a soft-faced shrinking mallet, start hammering  near the center and work the flange down gradually  toward both ends. The flange tends to buckle at the  bend because the material is made to occupy less  space. Work the material into several small buckles  instead of one large one and work each buckle  out gradually by hammering lightly and gradually  compressing the material in each buckle. The use of  a small hardwood wedge block aids in working out  the buckles.  [Figure 4-152] 4.  Planish the flange after it is flattened against the form  block and remove small irregularities. If the form blocks  are made of hardwood, use a metal planishing hammer.  If the forms are made of metal, use a soft-faced mallet.  Trim the excess material away and file and polish. 1.  Cut the material to size (allowing for trim), determine  bend allowance for a 90° bend, and round off the edge  of the block to conform to the desired radius of bend. 3.  Using a soft-faced stretching mallet, start hammering  near the ends and work the flange down smoothly and  gradually to prevent cracking and splitting. Planish  the flange and angle as described in the previous  procedure, and trim and smooth the edges, if necessary. 2.  Clamp the material in the form blocks.  [Figure 4-153] To form a flanged angle by stretching, use the same forming  blocks, wooden wedge block, and mallet as used in the  shrinking process and proceed as follows: The concave flange is formed by stretching, while the  convex flange is formed by shrinking. Such parts are  shaped with the aid of hardwood or metal forming blocks.  [Figure 4-154]  These blocks are made in pairs and are  Curved flanged parts are usually hand formed with a concave  flange, the inside edge, and a convex flange, the outside edge.  Curved Flanged Parts Stretching Figure 4-153.  Stretching a flanged angle.  Figure 4-154.  Forming blocks.  Figure 4-152.  Shrinking. 4-77