DE2312365B1 - Auger bits for drilling large holes in rock - Google Patents

Description

An embodiment of the invention is shown in the drawing and will be discussed in more detail below

wrote. It shows Fig. 1 part of a worm drill in the Front view, FIG. 2 also seen in the direction of the line A-B of Fig. 1, F i g. 3 is an enlarged illustration of a detail, partially broken away.

This auger bit has a replaceable attached to the shaft 1, double-bladed precutter 2, the hexagonal coupling pin 3 of which in the hollow, inside hexagonal shaft 1 is inserted. For fixing in the axial direction a cross pin 4 is used.

Each of the helically arranged wings 5 carries three Chisel 6.

Furthermore, on the screw conveyor 7, the width of the pre-cutter 2 starting over about a half Winding length increases, but then up to to the upper end part of the drill maintains the same width, four drill bits 8 interchangeable attached. The radial distance between the drill bit 8 and the drill axis increases from drill bit to drill bit by about twice the cutting width 9 of one Drill bit 8 to.

The drill bits 8 have a clearance angle 10 of approximately 15 ". For exchangeable Attachment to the screw conveyor 7, the drill bits 8 have a stepped pin 11, which is inserted into a corresponding hole 12 in the screw conveyor 7. For releasable locking of this plug connection, an angle to the pin is used 11 arranged clamping screw 13 which engages in an incision 14 of the pin 11.

Claims (4)

Claims: 1. Auger with a smaller diameter, at least two-winged pre-cutter and with one from the pre-cutter in the Increasing width of the screw conveyor for creating large boreholes in rock, starting at the roughing cutter along the side cutting edge several spaced apart arranged, axially parallel and aiming in the drilling direction drill bits with a cutting clearance angle of more than 5 ° are provided, their radial distance from the drill axis of Drill bit to drill bit increases, d a -characterized in that the precutter (2) per wing (5) with several spaced apart, forward, outwardly and in the direction of rotation aiming chisels (6) is provided, the cutting edge of which When turning the drill, describe a cone surface and the same one Have a cutting clearance angle of more than 5 °, and the screw conveyor (7) provided drill bit (8) in the radial direction by more than the cutting width the drill bit (8) are arranged offset from one another. 2. Auger according to claim 1, characterized in that at least the chisels (8) arranged on the screw conveyor each have an angular cutting edge have, the tip of which is arranged aiming in the drilling direction. 3. Auger according to claim 1, characterized in that the Chisels (6, 8) have a clearance angle of about 15 °. 4. Auger according to claim 1, characterized in that the radial distance of the drill bit (8) from the drill axis from drill bit to drill bit increases by about twice the cutting width (9). The invention relates to an auger bit with a diameter smaller, at least two-winged pre-cutter and with one from the pre-cutter from a screw conveyor increasing in width for the production of large boreholes in rock, with several starting at the cutting edge along the side cutting edge Drill bits arranged at a distance from one another, axially parallel and aiming in the drilling direction are provided with a cutting clearance angle of more than 5 °, their radial distance increases from drill bit to drill bit axis. In a known auger (US-PS 3,024,856) with an im Smaller diameter, two-winged pre-cutter and with one of the pre-cutter from the conveyor screw increasing in width and starting along the pre-cutter the side cutting edge of the screw conveyor arranged at a distance from one another, axially parallel and bits pointing in the direction of drilling are the bits of the roughing cutter and the chisels arranged on the screw conveyor are designed to be identical to one another and have cutting edges running at right angles to the drill axis with a cutting edge clearance angle of more than 5 ". Furthermore, the radial distance of the arranged on the screw conveyor increases Drill bit from bit to bit by less than the width of the cutting edge. From GB-PS 707 981 a rock drill of the type described above is known, in which, however, a massive pointed drill with three on the Circumferentially arranged, axially and pointed cutting is provided. In such rock drills that require a large torque and where the cuttings are very fine-grained, however, is the drilling performance relatively low. The invention is now based on the object for a worm drill to create opportunities to increase the drilling performance of the type described above. The solution to this problem is characterized according to the invention by that the pre-cutter per wing with several, spaced apart, forwards, outwards and in the direction of rotation aiming chisels is provided whose When turning the drill bit describe a cone surface and the same have a cutting clearance angle of more than 5 °, and that on the screw conveyor provided drill bit in the radial direction by more than the cutting width the drill bits are offset from one another. Dig through these measures Both the chisels of the precutter and those arranged on the screw conveyor Chisels into spaced apart zones and break them between The rock located in the grave zones, whereby the drill cuttings are much coarser-grained than occurs with the known auger bits. This means that for drilling with the subject of the invention either far less low torques than required for the known auger bits are, or that with the same torque a multiple increase in drilling performance is achieved. It is known ("Glückauf" magazine, July 5, 61, p. 831 and 5. 2. 70, p. 114) to adapt the radial distance of drill bits to the hardness of the rock, but these are roller bit combinations in which the rock pieces be knocked off by the chisel teeth. However, roller bits are far more complicated and expensive than auger bits. These references also reveal that in solid rock, like sandstone, large boreholes can only be produced economically with roller drills, although US Pat. No. 2,289,935 has long had a multi-winged precutter it was known that per wing several, spaced apart, forward, has outward and in the direction of rotation aiming chisels, the cutting of which when turning describe a cone surface of the drill. In the subject matter of the invention, it has also been found to be advantageous if at least the chisels arranged on the screw conveyor each have an angular Have cutting edge, the tip of which is arranged aiming in the drilling direction. In addition, they are advantageous for increasing drilling performance Contributing features in that the chisel has a Have clearance angles of about 150 and preferably also the radial distance the drill bit from drill bit to drill bit by about twice as much Cutting width increases.