[Fig. 2145] represents another common form of connecting rod strap, and in this case the pening may be most quickly and effectively done at the crown as denoted by the dots; and as this would alter the inside curve, the brass or box fitting into it must be refitted. In case the pening should be overdone it is better to modify it by filing away some of the pened surface.
Fig. 2146.
Cast iron is more rapidly affected by pening than either wrought iron or steel. One of the most useful applications of pening is in the case of moulding patterns, which in time may become warped from the rapping of the pattern in the mould, and this warping may be corrected by judicious pening, or suppose that a number of plates, such as represented in [Fig. 2146], having been cast, it is found that the ends of the tongues a b curl up when cooling in the mould, then the tongues may be pened as at c d, throwing them down to the requisite amount, and thus moulding the pattern to accommodate the curling in cooling.
The riveting usually performed by the machinist is generally upon cold metal. The blows in this case should fall dead and the riveting be performed with a view to stretching the metal uniformly and evenly over the surface to be riveted.
Fig. 2147.