Читать книгу The Handyman's Book of Tools, Materials, and Processes Employed in Woodworking - Paul N. Hasluck - Страница 125

The automatic screwdriver is made in variety, but the principle of all is much the same. The blade of the screwdriver, which is cylindrical throughout its length except for about 1 in. at the point, where it is flattened so as to enter the slot in the screw head, works in a hollow handle partly of brass and partly of wood. In using it the blade must be drawn out to its full length, and inserted in the slot of the screw, which is then driven home by pressure on the top of the handle (see Fig. 358), which by travelling down the spiral grooves in the spindle causes the blade to revolve. It is useful for rapidly driving a number of screws in a small space. If the blade is buried in its handle as far as may be, the tool can be used as any ordinary screwdriver for turning either forwards or backwards. A quick-action screwdriver (see Fig. 359), has a wooden handle of ordinary shape, into which slides a metal rod traversed from end to end by two spiral grooves—one right- and one left-handed—which receive an adjustable pin placed just inside the handle-sheath. A moderately strong coiled spring forces the rod outwards from the handle when not under pressure. The outer end of the rod is provided with adjustable jaws in which to hold slot bits. A turn of the ferrule at the end of the handle tightens the rod and admits of its being used as an ordinary screwdriver, while the twists necessary before the final tightening when driving in a screw or after the preliminary loosening when taking it out, are given very rapidly by Archimedean action following pressure of the handle in the direction of the tool’s length.

Fig. 357.—Plane iron Screwdriver.

Fig. 358.—Automatioc Screwdriver in use.

Fig. 359.—Millers Falls Automatic Screwdriver.