Both points should be sharpened, for although the centre leg is usually located by a punch mark, it may be required to mark dimensions when stepping-off points along a line.
Shears. The end portion of a pair of shears, as used by the tinsmith and sheet-metal worker, is depicted in Fig. 54, whilst reference to Fig. 55, showing the assembled blades in section, will make clear the cutting and shearing action of these members.
As the handles are closed, the line of contact between the cutting edges travels from the base of the blades towards their tips, ' and this close contact is maintained by giving a slight curvature lengthwise to one of the blades, also by providing a well-fitting pivot joint.
It will be apparent that, with continued use, wear will
take place on both the flat shear-face and on the inclined cutting-face of the blades. To resharpen the blades, therefore, each is in turn ground on both these faces, but before grinding, the blades should be separated by removal of the pivot-bolt or joint rivet.
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