Abstract: The present invention provides a drill bit sharpening device, for use with a support carrying a rotatable grindstone and having pivot arm retaining means. The device comprises a drill bit jig having clamp means for releasably retaining a drill bit therein in a position wherein the drill bit axis extends forward from the clamp means along a corresponding clamp axis. The clamp means has a first and second opposed jaw movable toward and away from one another so as to accommodate different diameter drill bits positioned therebetween. A jaw adjuster connected to the first jaw has a U-shaped frame with upper and lower threaded flanges extending over the second jaw. A nut adapted to mate with the threaded flanges is provided for securing the drill bit. A retaining guide is connected to the second jaw and is adapted to urge the second jaw away from the first one.

Abstract: Integral, elongated panels have sets of converging corrugations arranged on lines defined by folded, transversely triangular elements. These elements extend laterally across the panel, and are dimensioned such that a pair of adjacent parallel side edges of two corresponding panels can mate. Preferably, each corrugation has a planar element arranged on lines generally perpendicular to the side edges defining congruent elements with triangular faces meeting at the apex.By such arrangement, a panel is obtained which in conjunction with other such panels, can produce a curved surface, which curvature may be reversed in direction in any point along a structure surface, by inverting the next adjacent series of panels.

Abstract: Integral, elongated panels have sets of converging corrugations arranged on lines defined by folded, transversely triangular elements. These elements extend laterally across the panel, and are dimensioned such that a pair of adjacent parallel side edges of two corresponding panels can mate. Preferably, each corrugation has a planar element arranged on lines generally perpendicular to the side edge defining congruent elements with triangular faces meeting at the apex.By such arrangement, a panel is obtained which in conjunction with other such panels, can produce a curved surface, which curvature may be reversed in direction in any point along a structure surface, by inverting the next adjacent series of panels.

Abstract: Integral, elongated panels have sets of flanges arranged on lines which define folded, transversely triangular elements. These elements extend laterally across the panel, and are dimensioned such that a pair of adjacent parallel side edges of two corresponding panels can mate. The flanges preferably extend along the entire length of the lines defining the folded transversely triangular elements, and may usefully be linear and arranged on lines defining congruent elements with triangular faces, and sloping side edge portions of the panel. By such arrangement, a panel is obtained which in conjunction with other such panels, can produce a curved surface, which curvature may be reversed in direction in any point along a structure surface, by inverting the next adjacent series of panels.

Abstract: A sharpening device, particularly useful for sharpening tools having two identical cutting edges such as drill bits, comprised of a jig for holding a drill bit used with an adjustable support having a rotatable grindstone and a pivot arm retaining means. The jig has a clamp means for releasably retaining a tool or drill bit in it, and a frame. The frame is connected to the clamp means, and typically carries first and second pivot arms which are symmetrically disposed at an angle to the clamp axis. The first pivot arm is placed in the pivot arm retaining means of the support where the jig can rest in a first rest position in which the clamp axis extends forwardly to intersect a grinding face of a grindstone carried in the support, at a predetermined lateral angle of A.sub.1 thereto.