CONSTRUCTION OF BINDING SCREWS. 



657 



long, 15 mm wide, and 3 mm thick, a hole is drilled 8 mm from one end 

 and a hollow screw cut in it with the smallest of our screw-taps 

 (see page 94), or the middle-sized one. A piece of wire of suitable 

 diameter, and 3 cm long, is softened in the middle over the flame and 

 bent at right angles, clamping it in the vice and using the mallet. 

 The bent wire is clamped in the vice, so that one half lies hori- 

 zontally between the jaws and the other half stands out vertically, 

 and a screw is cut on the projecting half, which corresponds to the 

 nut previously cut. The piece which contains the nut is then bent 

 into the shape shown in the figure ; the side where the nut is must 



FIG. 337 (A, E, anproj. ; A to G real size). 



be clamped up to about 18 mm from the end in the vice between leaden 

 cheeks, in order to protect the nut, and the projecting portion bent 

 by hammering it with the mallet until it is horizontal.. The piece 

 is then taken out of the vice, and both halves are hammered together 

 over a flat piece of hard wood, about 5 mm thick, until they are 

 parallel, as in the figure. This operation may be rendered easier by 

 softening the metal previously ; but in afterwards using the clamp 

 the screw should never be drawn very tight, or the two halves will 

 be forced away from each other. This simple kind of binding screw 

 cannot be used for clamping the wires themselves ; but if the ends 

 of the wires have flat pieces of sheet copper soldered to them, in the 



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