Smiths' work - Tapa blanda

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1904 Excerpt: ... heavy, bending blocks are necessary. It is easier to bend bar-iron flatwise than edgewise; the reason is apparent if it is remembered that when a wide bar is bent two things happen. Along the centre of the bar(A, A, Fig. 110) there will be a neutral axis of metal that bends without Fig. 110.--Diagram to Illustrate Tension and Compression, compression or extension of fibre. But outside this neutral axis, the metal, B, B, is extended, and inside of this axis the metal, c, c, is compressed. The metal in tension and the metal in compression will seek relief from the intense stresses to which it is subjected. It will become wrinkled and puckered upwards and downwards. This tendency has to be corrected by hammering, or by the use of mechanical devices. Many devices are resorted to in bending work of various sections and outlines. The making of a special cast iron templet, or bending block, is a question of relative cost. Where only a few plain pieces have to be bent, it will not pay to make the simplest block. Where there are many pieces, all alike, it pays to cast most elaborate blocks, and to fit them up with clips and cottars, or whatever may be necessary besides. It is usually easy for the smith to design blocks for forgings which he may require. Fig. Ill shows a common type of block used for bending flat bars. Made in suitable sections, it is also often employed for bending T-iron. As shown, the working edge, A, is a circular arc; but it could be shaped to other curves equally well. The block has cast in it a stout cottared pin, projecting from its bottom face. This pin passes through a suitable hole in the levelling block, o, and is cottared beneath. For holding down cast-iron templet blocks, this is the most conve nient method--better than having movable ...