A glass article (100) includes a core layer (102) formed from a core glass composition with a core coefficient of thermal expansion (CTE) and first (104) and second (106) cladding layers fused to first and second major surfaces of the core layer (102) and formed from a clad glass composition comprising a clad CTE. An aperture (120) extends through each of the core layer (102), the first cladding layer (104), and the second cladding layer (106). The clad CTE is less than the core CTE such that each of the first (104) and second (106) cladding layers is under a compressive stress and the core layer (102) is under a tensile stress. A flexural strength of the glass article (100) can be at least about 75 MPa. A peak load sustainable by the glass article (100) in a modified ring-on-ring test can be at most 96.5% less than a peak load sustainable by a reference glass article in the modified ring-on-ring test.

A magnetic base for an electric machine tool, in particular for a magnetic core drilling machine. A body that is accommodated in a receiving space. At least one first magnet coil constituting an electromagnet, a coil winding of the at least one first magnet coild being wound on a bobbin and a magnetic force of which is switchable between a maximum resultant holding force and a minimum resultant holding force. The coil winding of the magnet coil has two end sections that are each connected to a connecting cable that serves to make electrical contact between the magnetic coil and the electric machine tool. The body has a first side adapted to be coupled to the electric machine tool and has an opposite second side adapted to be placed on a workpiece that is to be processed. End sections of the coil winding are connected to the connecting cables.

An insert tool, in particular a chisel or a drill, has a tool head, with a shaft region in which a main body is arranged. The main body has a first hardness, and with a coating which has a second hardness that is greater than the first hardness. The coating has chromium carbide or consists of chromium carbide. Advantageously, the durability of the insert tool can be prolonged as a result.

A method and apparatus is provided to rehabilitate and beautify cracked concrete surfaces by adding channels that look like the cracks to the surface.

A drill bit includes a drill bit head, a multi-strand helix made up of three or more helix ribs, and a shank end along a drill bit axis. The multi-strand helix is made up of a conveyance area, a helix gradient, and a pitch. The helix ribs extend parallel to the drill bit axis in a first area adjacent to the drill bit head and a second area adjacent to the shank end.

A tool head capable of introducing deep recesses into hard and brittle material such as glass and glass ceramics is provided. The tool head includes a hollow cylindrical abrasive body merging into a hollow shank. The hollow cylindrical abrasive body has an end face with a central abrasive area at the location of a cylinder axis. The central abrasive area is connected with the inner wall surface of the hollow cylindrical abrasive body by at least one web. The end face of the abrasive body, the web, and at least a portion of the outer wall surface of the abrasive body are covered with abrasive. The hollow shank has at least one opening to the interior between the at least one web and the inner wall surface of the abrasive body.

A method for producing a drill includes cold forming of a rod-shaped blank to form a semifinished product having three or more rectilinear longitudinal ribs extending along a longitudinal axis of the semifinished product, introducing the longitudinal ribs into a first die and a second die in a working direction, where the first die bears against the longitudinal ribs in a direction of rotation about the longitudinal axis and the second die bears against the longitudinal ribs counter to the direction of rotation, pivoting the first die in the direction of rotation in relation to the second die in order to twist the longitudinal ribs between the first and second dies, pulling the longitudinal ribs 31 through the pivoted first die and the second die counter to the working direction in order to twist the longitudinal ribs and apply a drill head to the rear end in the working direction.

A method for setting a screw, which has an external thread in a front region and a drive in a rear region for introducing a torque into the screw, in a drilled hole in a substrate of a mineral material includes producing an internal thread in the drilled hole by a threaded drill provided with a cutting thread and then introducing the screw into the drilled hole and in so doing the external thread of the screw is screwed into the internal thread, produced by the threaded drill, in the drilled hole. The external diameter of the cutting thread of the threaded drill is smaller than the external diameter of the external thread of the screw.

A drill bit that serves to remove mineral materials and that consecutively has on a longitudinal axis (6) a drill head (2), a helix (3), an insertion end (4) and an impact surface (7) on the end face of the insertion end (4) that faces away from the drill head (2) and that serves to absorb impact along a direction of impact (8), is provided. The drill head (2) has at least two cutting edges (13) and at least two blades (20). The cutting edges (13) each have a cutting face (16) and a free face (17). The blades (20) run parallel to the longitudinal axis (6) and adjoin the cutting edges (13). The blades (20) each have a radially projecting tooth (24) that adjoins the cutting face (16), whereas it adjoins the free face (17) either only partially or not at all. The axial dimension (29) of the tooth (24) is smaller than the axial dimension (25) of the blade (20).

A drilling device for forming an enlarged-diameter hole includes: a guide sleeve with a cylindrical body and a guide to be inserted into a bottomed hole; a slide body that slides in the cylindrical body; and a bit holder provided on the slide body swingably; and a diameter-enlarging bit with a cutting blade. The bit slides between a first position where the cutting blade is separated from a bottom of the bottomed hole and a second position where the cutting blade is closer to the bottom than that at the first position. The guide has: a guide piece that guides the cutting blade to a side part, of the bottomed hole, following an advance of the bit from the first position to the second position; and an opening which allows passage of the bit removed from the bit holder where the bit is at the first position.