WO1993001921A1 - Drill bit - Google Patents

Drill bit Download PDF

Info

Publication number
WO1993001921A1
WO1993001921A1 PCT/SE1992/000510 SE9200510W WO9301921A1 WO 1993001921 A1 WO1993001921 A1 WO 1993001921A1 SE 9200510 W SE9200510 W SE 9200510W WO 9301921 A1 WO9301921 A1 WO 9301921A1
Authority
WO
WIPO (PCT)
Prior art keywords
edges
pilot
drill bit
main radial
longitudinal sides
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/SE1992/000510
Other languages
French (fr)
Inventor
Erik Sundström
Gaudenz CALÖRTSCHER
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sandvik AB
Original Assignee
Sandvik AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sandvik AB filed Critical Sandvik AB
Priority to DE69205830T priority Critical patent/DE69205830T2/en
Priority to US08/175,346 priority patent/US5452970A/en
Priority to EP92915752A priority patent/EP0594746B1/en
Publication of WO1993001921A1 publication Critical patent/WO1993001921A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27G—ACCESSORY MACHINES OR APPARATUS FOR WORKING WOOD OR SIMILAR MATERIALS; TOOLS FOR WORKING WOOD OR SIMILAR MATERIALS; SAFETY DEVICES FOR WOOD WORKING MACHINES OR TOOLS
    • B27G15/00—Boring or turning tools; Augers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T408/00—Cutting by use of rotating axially moving tool
    • Y10T408/89—Tool or Tool with support
    • Y10T408/899—Having inversely angled cutting edge
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T408/00—Cutting by use of rotating axially moving tool
    • Y10T408/89—Tool or Tool with support
    • Y10T408/905—Having stepped cutting edges
    • Y10T408/906—Axially spaced
    • Y10T408/9065—Axially spaced with central lead
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T408/00—Cutting by use of rotating axially moving tool
    • Y10T408/89—Tool or Tool with support
    • Y10T408/909—Having peripherally spaced cutting edges

Definitions

  • Flat bits are commonly used for drilling of holes with diameter 10 to 40 mm (3/8 to 1 1/2 inch) in wood with electric hand drills. Since they are not self-feeding it i ⁇ easy to control the penetration into the workpiece, and they are thus used above all for shallow holes and for through holes in relatively thin workpieces.
  • Simple flat bits consist of a shaft and a flat part made as a plate with substantially even thickness, a triangular pilot point, two substantially radial main cutting edges and two substantially parallel non-cutting longitudinal edges.
  • the shaft is attached to the flat part by welding, by brazing or by a threaded connection. It is in general required that flat bits should be possible to resharpen by filing.
  • the purpose of the pilot point is to commence the drilling of the hole at a well defined center, to stabilize the drill bit when the radial edges start to cut in order to get a clean non-splintered perimeter at the entry side, and when a through hole is to be drilled to make a pilot hole with small diameter in order to locate and guide the drill when the last part of the hole is drilled from the reverse side of the workpiece.
  • the purpose of the main radial edges is to cut and transport chips with a low and even force, and to form the major part of the bottom surface of a dead end hole.
  • a pilot point with even thickness offers acceptable stability but has a large negative rake angle, leading to high cutting force, unsatisfactory chip transport and overheating when drilling in resinous or hard wood. It will also deviate to the side if the hardness of the workpiece is not homogeneous, as in drilling parallel to the fibers or near a knot. The same problems but less serious are found with pyramid-shaped points.
  • a pilot point which has grooves along the edge according to US 2,782,824 has positive rake angle, lower cutting force and better defined position, but will not stabilize the drill well enough when the force on the the main cutting edges varies. All triangular pilot points will also cause a parallel error and lack of accuracy when a through hole is drilled at some other angle than normal to the surface of the workpiece.
  • a drill bit with a pilot point with partly parallel sides is described in US 2,543,206 and provides good stability and good guiding in through holes, but other features of this drill bit restrict it to drilling with high rpm, slow penetration and limited diameter. Pilot points where the width decreases near the main radial edges are known from US 3,920,350 and lead to somewhat less cutting force but less stability.
  • the main radial cutting edges are normally located at an angle of 70 to 90 degrees to the drill axis, 90 degrees giving the lowest cutting force when drilling at right angle to the fibres but a greater risk of uneven or splintered perimeter except when drilling with very low feed rate.
  • a smaller angle produces a neater perimeter, less vibrations when entering the workpiece and has less requirements for stabilizing, but needs more cutting force and wears more rapidly.
  • If grooves are made parallel to the main radial edges the rake angle will be positive and the cutting force lower, but the perimeter less neat.
  • the invention is a flat drill bit which better than previous types can fill the different requirements.
  • a new design of the outer ends of the main radial edges makes it possible to acheive at the same time a satisfactory hole perimeter, simple resharpening, and low and smooth cutting forces which are simple to stabilize with the pilot point when the main radial edges start cutting.
  • the radial component of the cutting force at each main radial edge can be made so small that there is no difficulty in producing holes overlapping each other or the workpiece edge.
  • the new design of the outer ends of the main radial edges means that a minor portion of the substantially parallel longitudinal sides of the plate are made as cutting edges with positive rake angle, but without any extending spurs.
  • a flat drill bit according to the invention comprises a plate (12) and a shank (10) the free end (11) of which can be designed for easy clamping by a drill chuck, with three or six flat surfaces.
  • the plate has two longitudinal sides (16,17) which are substantially parallel or preferrably slightly converging towards the shank end, forming an angle not over 2 degrees with the axis of the shank (10) , two main radial edges (14,15) forming an angle of from 65 to 90 degrees, preferrably from 70 to 85 degrees, with the axis of the shank (10) , and a pilot point with two converging pilot edges (18,19) .
  • the main radial edge (14) and the pilot edge (18) moving forward are provided with grooves (20,21) milled, ground or swaged along the edges to make the rake angle positive, at least 5 degrees at the main radial edge (14) .
  • the longitudinal sides of the plate are blanked or ground at an angle to the faces to provide a relief angle.
  • the width and depth of the grooves (20,21) are substantially constant along the whole edges (14,18) except in a small region near the end of the main radial edge (14) at the longitudinal side (16) , where the depth of the groove is rapidly reduced to create a short lateral edge (26) with positive rake angle.
  • the lateral edge (26) meets the main radial edge (14) in a corner with a slightly acute angle, but without forming a protruding spur.
  • the length of the lateral edge (26) can be equal to the width of the groove (21) as shown in figure 1, or the lateral edge (24) can be slightly longer by provision of a groove (25) along a portion of the longitudinal side (16) .
  • the groove (20,21,25) section is preferrably unsymmetric with the deeper parts farther from the edge than half the width of the groove.
  • the drill bit can then be resharpened more times before the rake angle becomes disadvantageous.
  • pilot point is made with both converging pilot edges
  • the parallel sides (27,28) should be so long that they at least to some extent have entered the workpiece before the main radial edges (14,15).
  • a drill bit according to the invention has positive rake angle at the main radial edge (14) as well as at the first cutting edge part (24,26) of the longitudinal side (16). The cutting force is then much lower, and easier to balance with forces ' on the pilot point.

Landscapes

  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Wood Science & Technology (AREA)
  • Forests & Forestry (AREA)
  • Drilling Tools (AREA)

Abstract

Flat drill bit for drilling holes in wood, comprising a plate (12) with two longitudinal sides (16, 17), two main radial edges (14, 15) and a pilot point with two converging pilot edges (18, 19), where main radial edges, pilot edges and short lateral edges (24, 26) being short portions of the longitudinal sides, all have positive rake angle produced by grooves parallel to the edges facing forwards during rotation. For larger diameters the pilot point has two converging pilot edges and two parallel sides (27, 28).

Description

DRILL BIT
Background
Flat bits are commonly used for drilling of holes with diameter 10 to 40 mm (3/8 to 1 1/2 inch) in wood with electric hand drills. Since they are not self-feeding it iε easy to control the penetration into the workpiece, and they are thus used above all for shallow holes and for through holes in relatively thin workpieces.
Simple flat bits, described in the patents US 2,794,468 and US 4,066,379 consist of a shaft and a flat part made as a plate with substantially even thickness, a triangular pilot point, two substantially radial main cutting edges and two substantially parallel non-cutting longitudinal edges. The shaft is attached to the flat part by welding, by brazing or by a threaded connection. It is in general required that flat bits should be possible to resharpen by filing.
The purpose of the pilot point is to commence the drilling of the hole at a well defined center, to stabilize the drill bit when the radial edges start to cut in order to get a clean non-splintered perimeter at the entry side, and when a through hole is to be drilled to make a pilot hole with small diameter in order to locate and guide the drill when the last part of the hole is drilled from the reverse side of the workpiece.
The purpose of the main radial edges is to cut and transport chips with a low and even force, and to form the major part of the bottom surface of a dead end hole.
These different purposes set partly conflicting requirements for the design of the flat bit, and it has been difficult to satisfy all to an acceptable extent, in spite of many improvements on the original design. A pilot point with even thickness offers acceptable stability but has a large negative rake angle, leading to high cutting force, unsatisfactory chip transport and overheating when drilling in resinous or hard wood. It will also deviate to the side if the hardness of the workpiece is not homogeneous, as in drilling parallel to the fibers or near a knot. The same problems but less serious are found with pyramid-shaped points. A pilot point which has grooves along the edge according to US 2,782,824 has positive rake angle, lower cutting force and better defined position, but will not stabilize the drill well enough when the force on the the main cutting edges varies. All triangular pilot points will also cause a parallel error and lack of accuracy when a through hole is drilled at some other angle than normal to the surface of the workpiece.
A drill bit with a pilot point with partly parallel sides is described in US 2,543,206 and provides good stability and good guiding in through holes, but other features of this drill bit restrict it to drilling with high rpm, slow penetration and limited diameter. Pilot points where the width decreases near the main radial edges are known from US 3,920,350 and lead to somewhat less cutting force but less stability.
The main radial cutting edges are normally located at an angle of 70 to 90 degrees to the drill axis, 90 degrees giving the lowest cutting force when drilling at right angle to the fibres but a greater risk of uneven or splintered perimeter except when drilling with very low feed rate. A smaller angle produces a neater perimeter, less vibrations when entering the workpiece and has less requirements for stabilizing, but needs more cutting force and wears more rapidly. If grooves are made parallel to the main radial edges the rake angle will be positive and the cutting force lower, but the perimeter less neat. It is known from the patent US 4,682,917 to make spurs protruding from the outer ends of the main radial edges in order to sever the fibers before they are touched by the main radial edges. This allows main radial edges at 90 degrees to the drill axis and positive rake angle, producing neat holes with low cutting force, but this type of drill cannot easily be resharpened.
Purpose of the invention
The invention is a flat drill bit which better than previous types can fill the different requirements. A new design of the outer ends of the main radial edges makes it possible to acheive at the same time a satisfactory hole perimeter, simple resharpening, and low and smooth cutting forces which are simple to stabilize with the pilot point when the main radial edges start cutting. The radial component of the cutting force at each main radial edge can be made so small that there is no difficulty in producing holes overlapping each other or the workpiece edge.
This allows a pilot point with positive rake angle in order to give low cutting force, or for large diameters a combination of positive rake angle and partially parallel sides, to give excellent stability and precision for through holes.
The new design of the outer ends of the main radial edges means that a minor portion of the substantially parallel longitudinal sides of the plate are made as cutting edges with positive rake angle, but without any extending spurs.
This will make it possible to balance not only the radial forces from the corner, but also the radial force component appearing along the main radial edge which due to the finite thickness of the plate is not perpendicular to its local direction of motion.
Description The invention is described with reference to figures 1 and 2, showing alternative embodiments of flat drill bits according to the invention, figure 3 showing a cross- section through the pilot point and figure 4 showing a cross-section close to the main radial edges.
A flat drill bit according to the invention comprises a plate (12) and a shank (10) the free end (11) of which can be designed for easy clamping by a drill chuck, with three or six flat surfaces. The plate has two longitudinal sides (16,17) which are substantially parallel or preferrably slightly converging towards the shank end, forming an angle not over 2 degrees with the axis of the shank (10) , two main radial edges (14,15) forming an angle of from 65 to 90 degrees, preferrably from 70 to 85 degrees, with the axis of the shank (10) , and a pilot point with two converging pilot edges (18,19) .
On each face of the plate (12) the main radial edge (14) and the pilot edge (18) moving forward are provided with grooves (20,21) milled, ground or swaged along the edges to make the rake angle positive, at least 5 degrees at the main radial edge (14) . The longitudinal sides of the plate are blanked or ground at an angle to the faces to provide a relief angle.
The width and depth of the grooves (20,21) are substantially constant along the whole edges (14,18) except in a small region near the end of the main radial edge (14) at the longitudinal side (16) , where the depth of the groove is rapidly reduced to create a short lateral edge (26) with positive rake angle. The lateral edge (26) meets the main radial edge (14) in a corner with a slightly acute angle, but without forming a protruding spur. The length of the lateral edge (26) can be equal to the width of the groove (21) as shown in figure 1, or the lateral edge (24) can be slightly longer by provision of a groove (25) along a portion of the longitudinal side (16) .
The groove (20,21,25) section is preferrably unsymmetric with the deeper parts farther from the edge than half the width of the groove. The drill bit can then be resharpened more times before the rake angle becomes disadvantageous.
In the alternative version shown in figure 2, which is preferrably used for diameters above 20 mm (3/4 inch) the pilot point is made with both converging pilot edges
(18,19) and parallel sides (27,28), with the parallel sides preferrably made with zero relief angle or slightly rounded to give maximal stability against unbalanced radial forces at the main radial edges (14,15) and the lateral edges (24,26). The parallel sides (27,28) should be so long that they at least to some extent have entered the workpiece before the main radial edges (14,15).
When drilling a hole with a drill bit according to figure 2 the first part of the hole is drilled from the front of the workpiece far enough that the parallel sides (27,28) of the pilot point have penetrated the reverse side of the workpiece, and the last part of the hole from the reverse side. Since the parallel sides will then follow a a cylindrical pilot hole the first and last parts of the hole will match perfectly and the hole perimeter on the reverse side will be free of splinters and chipping.
When drilling a hole at an oblique angle to the workpiece surface the critical moment is when the outer end of the main radial edge (14) starts to cut into the surface. If the cutting force at this end is larger than the forces at the pilot point, there is a risk that the drill bit will rotate around some other axis than the pilot point, and damage the workpiece surface. The risk is especially great if the main radial edge (14) joins a non-grooved longitudinal side (16) . A drill bit according to the invention has positive rake angle at the main radial edge (14) as well as at the first cutting edge part (24,26) of the longitudinal side (16). The cutting force is then much lower, and easier to balance with forces' on the pilot point. For large diameter drills the high tangential velocity will increase the cutting force at the outer end of the main radial edge (14) , and to balance this with higher forces at the pilot point it is advantageous to make the pilot point with partly parallel sides (27,28) according to figure 2. A very great force would then be needed to tear the pilot point from its hole in the work piece.

Claims

1. Flat drill bit for drilling holes in wood, comprising a plate (12) with two substantially parallel longitudinal sides (16,17), two main radial edges (14,15) at their outer ends forming acute angles with the longitudinal sides
(16,17) without protruding spurs, and a pilot point which has two converging pilot edges (18,19) along at least part of its length, c h a r a c t e r i z e d by having positive rake angle at the pilot edges (18,19), at the main radial edges (14,15) and at short lateral edges (24,26) which are portions of the longitudinal sides (16,17), said positive rake angle being produced by grooves (20,21,25) along the edges facing forwards during rotation.
2. Flat drill bit according to claim 1, c h a r a c t e r i z e d by the length of the lateral edges (24,26) being not less than the width of the groove
(21) along the main radial edge and being not more than half the length of the longitudinal sides (16,17).
3. Flat drill bit according to claim 1, c h a r a c t e r i z e d by the pilot point having two converging pilot edges (18,19) and two parallel sides (27,28) .
4. Flat drill bit according to claim 3, c h a r a c t e r i z e d by the parallel sides (27,28) being made without clearance angle.
5. Flat drill bit according to claim 3, c h a r a c t e r i z e d by the parallel sides (27,28) being rounded.
PCT/SE1992/000510 1991-07-15 1992-07-07 Drill bit Ceased WO1993001921A1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
DE69205830T DE69205830T2 (en) 1991-07-15 1992-07-07 DRILL CHISEL.
US08/175,346 US5452970A (en) 1991-07-15 1992-07-07 Drill bit
EP92915752A EP0594746B1 (en) 1991-07-15 1992-07-07 Drill bit

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9102180-8 1991-07-15
SE9102180A SE468708B (en) 1991-07-15 1991-07-15 FLAT DRILL

Publications (1)

Publication Number Publication Date
WO1993001921A1 true WO1993001921A1 (en) 1993-02-04

Family

ID=20383330

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1992/000510 Ceased WO1993001921A1 (en) 1991-07-15 1992-07-07 Drill bit

Country Status (5)

Country Link
US (1) US5452970A (en)
EP (1) EP0594746B1 (en)
DE (1) DE69205830T2 (en)
SE (1) SE468708B (en)
WO (1) WO1993001921A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU784668B2 (en) * 2001-12-05 2006-05-25 Sandvik Intellectual Property Ab A plate drill bit with multiple prongs
CN106994585A (en) * 2016-01-25 2017-08-01 洲晟实业股份有限公司 Method for manufacturing woodworking flat drill

Families Citing this family (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4409631C1 (en) * 1994-03-09 1995-11-09 Sfs Ind Holding Ag Self-drilling fastener with a plate-shaped drilling part
US5842267A (en) * 1994-12-30 1998-12-01 Black & Decker, Inc. Method and apparatus for forming parts of a predetermined shape from a continuous stock material
US6290439B1 (en) 1994-12-30 2001-09-18 Black & Decker, Inc. Method and apparatus for forming parts from a continuous stock material and associated forge
US5700113A (en) * 1994-12-30 1997-12-23 Black & Decker Inc. Spade-type boring bit and an associated method and apparatus for forming metallic parts
AUPN119295A0 (en) * 1995-02-17 1995-03-16 W.A. Deutsher Pty Ltd Attaching sheet material to a support
USD376809S (en) 1995-11-07 1996-12-24 Black & Decker Inc. Spade-type boring bit
USD394663S (en) 1996-03-25 1998-05-26 Black & Decker Inc. Spade-type boring bit having chamfered corner portions
US6227774B1 (en) * 1999-06-24 2001-05-08 Tetrason Diversified Corp. Spade drill bit
US6957937B2 (en) * 2001-02-20 2005-10-25 Maxtech Manufacturing Inc. Spade bits with angled sides
WO2003092938A1 (en) * 2002-04-30 2003-11-13 Iqbal Singh Spade-type drill bit having helical configuration
US7147414B2 (en) * 2002-06-27 2006-12-12 Allied Machine & Engineering Corp. Spur point drill insert
US20080101879A1 (en) * 2006-10-31 2008-05-01 Durfee Laverne R Spade-type bit
US7473056B2 (en) * 2005-10-20 2009-01-06 Irwin Industrial Tool Company Spade bit
US20080202780A1 (en) * 2007-02-28 2008-08-28 Reiter John P Power Drill Accessory for Loosening Soil
US8979444B2 (en) * 2007-06-07 2015-03-17 Robert Bosch Gmbh Cutting bit adapted to cut metal and wood and associated method
US7887269B2 (en) * 2007-10-10 2011-02-15 Robert Bosch Gmbh Spade bit with improved cutting geometry
US20090136306A1 (en) * 2007-11-26 2009-05-28 Howard Russell J Planing Apparatus And Method
USD608801S1 (en) 2009-07-20 2010-01-26 Techtronic Power Tools Technology Limited Drill bit
WO2015109485A1 (en) 2014-01-23 2015-07-30 杭州巨星工具有限公司 Flat drill bit
CN104802245B (en) * 2014-01-23 2019-07-09 杭州巨星工具有限公司 Chit drill
CN105014125B (en) * 2015-08-07 2018-05-29 杭州航天电子技术有限公司 A kind of double-sided blade fluting chit drill suitable for rotating processing
USD1049186S1 (en) * 2022-12-20 2024-10-29 Disston Company Drill bit
USD1056005S1 (en) * 2023-02-21 2024-12-31 Shanghai Dragon-Star Tools Co., Ltd. Drill

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2782824A (en) * 1954-04-27 1957-02-26 Irwin Auger Bit Company Flat or spade type wood boring bit
US4682917A (en) * 1986-01-24 1987-07-28 The Irwin Company Spade bit with fluted shoulders

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1221247A (en) * 1915-11-27 1917-04-03 Samuel W Traylor Drilling, reaming, and centering machine.
US2543206A (en) * 1948-07-23 1951-02-27 Benjamin D Aufderheide High-speed wood-boring bit
US3997279A (en) * 1975-01-20 1976-12-14 Parker Manufacturing Co. Drill bit
US4043698A (en) * 1976-11-02 1977-08-23 Rodney Chelberg Drill attachment

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2782824A (en) * 1954-04-27 1957-02-26 Irwin Auger Bit Company Flat or spade type wood boring bit
US4682917A (en) * 1986-01-24 1987-07-28 The Irwin Company Spade bit with fluted shoulders

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU784668B2 (en) * 2001-12-05 2006-05-25 Sandvik Intellectual Property Ab A plate drill bit with multiple prongs
CN106994585A (en) * 2016-01-25 2017-08-01 洲晟实业股份有限公司 Method for manufacturing woodworking flat drill

Also Published As

Publication number Publication date
DE69205830D1 (en) 1995-12-07
SE468708B (en) 1993-03-08
EP0594746A1 (en) 1994-05-04
SE9102180L (en) 1993-01-16
DE69205830T2 (en) 1996-04-04
SE9102180D0 (en) 1991-07-15
US5452970A (en) 1995-09-26
EP0594746B1 (en) 1995-11-02

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