Patent GB-1425368-A (GB)
Title: Point sharpening machine for drills
IPC: B24B3/26
Filed: 1973-02-19
Abstract: 1425368 Grinding drills HAWERA PROBST KG HARTMETALL - WERKZEUGFABRIK RAVENSBURG 19 Feb 1973 [17 Feb 1972 15 Jan 1973] 8073/73 Heading B3D A machine for grinding the point of a drill 20, Fig. 5, such as a twist drill, comprises a drill holder 26, and at least two sharpening tools 10, Figs. 1 and 3, such as diamond grinding wheels, arranged with offset axes to form a recessed working area 68 along which the drill moves relative to the tools. As described, each tool 10 is in the form of a grinding wheel having coarse, medium and fine sections 11, 12, 13, Fig. 2. The wheels are mounted on adjacent end of spindles 5 in respective headstocks 4 vertically adjustable by screws 7 on a guide 6 to adjust the shape of the re-entrant working area about a central plane 69. The headstocks are adjustable towards and away from the drill holder by a spindle 9. The outer ends of the spindles 5 have pulleys 14 connected by elastic belts to pulleys 15 on the opposite ends of the shaft of a motor 17 on a base 2. A pair of guide rods are mounted on the base parallel to the axes of the grinding wheel spindles 5 and slidably mount a support 19 for movement between adjustable abutments 21. A block 22 is adjustable about a bolt 23 on the support and can be secured in position by screws 24. An arm extends from the block and has a guide 25 along which a carriage 31 is adjusted by a spindle 38. A fork 32 on the carriage supports the drill holder for movement about a horizontal axis 28. The drill holder consists of a sleeve 33, Fig. 5, in which is a supporting sleeve 35 having a ring 36 formed with a diametral slot engageable by a spring-pressed detent 37 whereby the drill 70 is inclined through 180 degrees. An intermediate sleeve 77 is disposed within sleeve 35 and has a disc 79 which bears through a dish spring 74 against ring 36 so that the sleeve 77 is frictionally rotatable relative to the sleeve 35. A clamping tube 42 and sleeve 39 are disposed within sleeve 77 and the rear end of tube 42 has screwed thereon a sleeve 47 for a clamping spindle 46 which acts through a bolt 49 on the sleeve 39 to move it forwardly relative to tube 42 so that an inner cone 41 acts on collets 76 retained by a nut 81 to grip the drill 70. An ejector bolt 48 is located within the sleeve 39 and urged forwardly by a spring 50. A spring 44 urges the sleeve 39 towards its release position. A bearing 51 on the carriage 31 supports an aligning means 52 for the clamping tube 42 and a supporting means 55 for the front end of the drill. An abutment (53, Fig. 4, not shown) can be pivoted in alignment with the drill axis whereby when the drill is released, the ejector bolt urges the drill into contact with the abutment to position the drill axially. A microscope 57 is mounted on a carriage 59 movable along an axis 58, Fig. 2, parallel to the axis of the drill. The guides for the carriage are adjustable about a vertical axis 60 in a support 61 in a bearing 62 in a frame 1 on the base 2. The drill to be sharpened is placed in the drill holder and clamped therein by turning spindle 46. The abutment (53) is placed in front of the drill so that upon temporary release of the drill by action of the spindle 46, the ejector spring urges a drill against the abutment. The abutment (53) is retracted and the support 19 is moved to position the drill in alignment with the microscope and a handle 45 turned to rotate sleeve 39 to align the cutting edges of the drill with a crosswire in the microscope. Thereafter the support 19 is moved to carry the drill so that one face of the end of the drill is ground by passage through the re-entrant area 68, the drill being at an angle to the central horizontal plane 69 of the area. The drill is fed towards the grinding wheels by rotation of spindle 38. Thereafter, the drill is indexed through 180 degrees for grinding the outer face. In another embodiment, the drill holder is pivotable about a vertical axis between a position in which the end of the drill is presented to the grinding area with the drill axis inclined to the axes of the grinding wheels and a position in which the drill axis is parallel to that of the grinding wheels and its end can be observed in a microscope.