A DRILL JIG FOR DOWEL JOINTS

Abstract: A drill jig for preparing dowel joints between two work­ pieces (50, 52) to be interconnected end-face to side-face, has a guide hole (5) for drilling into the end face of workpiece (50) arranged parallel to bearing surface (7) against which work­ piece (50) abuts and a guide bore (8) for drilling into the side face of workpiece (52) arranged parallel to a positioning zone (10) against which workpiece (52) abuts. The longitudinal axes of the guide hole (5) and guide bore (8) define a right angle. In each embodiment the bearing surface (7) and positioning zone (10) lie completely inside or completely outside that right angle.

Description: A DRILL JIG FOR DOWEL JOINTS This invention relates to a drill jig for preparing dowel joints between two workpieces to be interconnected end-face to side-face. A prior art drill jig is disclosed in German OS 31 05 180. This drill jig comprises two members, namely a one-piece jig member having two portions extending at right angles to one another, and a second member which is slidably connected to the jig member. The second member is connected to the jig member on the side of an arm thereof, lying opposite a bearing surface thereon for a workpiece which is to be drilled on its end face. This connection may be for example, via rods attached to the jig member or an elongation of the jig member, so that the distance between the arm of the jig member and the second member may be adjusted in accordance with the thickness of the other workpiece which is to be drilled on its side face. The second slidable member is provided with the guide bores for making the bores in the workpiece which is to be drilled on its side face. The rods on the jig member or the elongation of the jig member define a positioning zone for the alignment of this workpiece in relation to the guide bores in the second member. This prior art drill jig enables workpieces of different thicknesses to be machined, the second member being slid for the purpose of adaptation to varying workpiece thickness. During machining the two workpieces lie parallel with one another, the arm of the jig member forming the bearing surface being disposed between them. Another drill jig is also known (German Patent Specification 24 37 724) in which both a bearing surface and a guide hole and also a positioning zone and bore hole are formed on and in a single jig member, in order to provide workpieces to be interconnected end-face to side-face with associated bores. However, with that prior art drill jig for drilling purposes the workpieces must be arranged at right angles to one another in the manner of their subsequent connection. This arrangement of the workpieces relative to the drill jig causes considerable retaining difficulties, more particularly in the machining of large boards. The present invention seeks to provide a drill jig for preparing dowel joints, in which the workpieces to be interconnected end-face to side-face are retained parallel with one another for the production of the bores, in which said workpieces contact respective guide surfaces of the jig member, and in which no guide surfaces must be displaced for adaptation to the dimensions of the workpieces. According to one aspect of the present invention there is provided a drill jig for preparing dowel joints between two workpieces to be interconnected end-face to side-face, comprising a jig member having a bearing surface for the workpiece which is to be drilled at its end face, at least one guide hole extending parallel to the bearing surface, a positioning zone extending perpendicularly to the bearing surface and against which positioning zone abuts in use the end face of the workpiece which is to be drilled on its side face, at least one guide bore extending parallel with the positioning zone, the longitudinal axes of said guide bore and said guide hole extending perpendicular to one another in the same plane, the distance between said axis of said guide bore and said positioning zone being equal to the distance between said axis of said guide hole and said bearing surface, characterised in that the bearing surface and the positioning zone lie completely inside or completely outside the right angle enclosed by said longitudinal axes of the guide hole and the guide bore. In preferred embodiments said jig member is formed as a one piece jig member which is open on at least three sides. The guide hole extends through an inner surface which is at right angles to the bearing surface. The guide hole and guide bore have the same diameter. The positioning zone and said at least one guide bore are integral with said one piece jig member. In one embodiment of the invention the positioning zone and the bearing surface lie completely inside the right angle enclosed by the longitudinal axes of the guide hole and the guide bore, the guide hole extends through an inner surface at right angles to said bearing surface, the bearing surface lies between the inner surface and the positioning zone, and the positioning zone terminates at that surface of the jig member through which the guide bore extends. The bearing surface and positioning zone thus form a shoulder between guide hole and guide bore. In use the workpiece, which is to be drilled at the end face, is arranged to bear against the bearing surface. Also, in use, the workpiece, which is to be drilled on the side face, made to lie against the afore-mentioned workpiece with its end face against the positioning zone. Thus arranged the two workpieces are disposed in parallel, with their corresponding end faces offset. In this position both the end-face bore in one workpiece, and the side-face bore in the other workpiece may be produced at the required places by means of the drill jig. In another embodiment of the invention, wherein the positioning zone and the bearing surface lie completely outside the right angle enclosed by the longitudinal axes of the guide hole and the guide bore, and said guide hole extends through an inner surface at right angles to said bearing surface, and the positioning zone is formed by the inner surface, and the bearing surface is formed by that surface of the jig member through which the guide bore extends. In this embodiment also for machining the two workpieces to be machined are disposed in parallel and with their end faces disposed in an offset relation. This allows for a bore to be produced through the guide bore on the side face of the workpiece bearing via its end face against the positioning zone without hindrance from the other workpiece. The other workpiece lies between the guide bore and the workpiece to be machined and is to be drilled at its end face through the guide hole. Hindrance is avoided since the end face (to be drilled) is in this manner arranged to be outside the machining zone of the guide bore. In the context of so arranging the end face (to be drilled), it is a preferred feature to provide stops disposed outside the zone of the guide bore and adjacent that surface of the jig member through which the guide bore extends, said stops extend to beyond the side of the guide bore remote from said inner surface. The end face (to be drilled) abuts the stops and is therefore retained outside the zone of the guide bore. When using the drill jig, the two workpieces may be interconnected by screw clamps in conventional manner. This clamping of the workpieces allows the drill jig to be moved along the workpiece edges without the risk that the workpieces may become displaced in relation to one another: if the workpieces are displaced, the bores/holes are misaligned and joints cannot be made. A preferred feature enables the drill jig to be retained in a fixed position during the making of two associated bores whereby the bores produced are in alignment with one another when the workpieces are connected. According to this preferred feature, an arm of the jig member is arranged, opposite a zone of the jig member, said zone defining said at least one guide bore and a clamping arranged with its clamping end extending out of the arm on the side adjacent the guide bore. The screw clamp enables that workpiece, which is to be drilled at the end face, to be presed tightly against the bearing surface, thus fixing the position of the drill jig. It may be that the two workpieces to be machined are not to be so interconnected that one surface of the workpiece, which is to be drilled at the end face, is in alignment with the corresponding end face of the other workpiece, which is to be drilled on the side face. Instead the workpiece which is to be drilled at the end face, may be required to be applied a location intermediate the length of the other workpiece, which is to be drilled on the side face. In that event it is impossible to place the workpieces into suitable positions relative to the guide hole and guide bore if one follows the manner of positioning the workpieces at the bearing surface and positioning zone afore described. However, to enable the drill jig according to the invention to be used even in that event, it is a preferred feature that a flat outer side of the jig member is parallel with the positioning zone and extends at right angles to the longitudinal axis of said at least one guide hole, and a pin-receiving bore is provided in the outside of that zone of the jig member which has at least one guide bore, said pin-receiving bore extending parallel with the guide bore with its longitudinal axis lying in the plane of the longitudinal axes of guide hole and guide bore, the distance of said pin-receiving bore from the outer side of the jig member is equal to the distance between the bearing surface and the guide hole. It is also a preferred feature that a pin is provided for insertion in the pin-receiving bore, said pin having a head which has a diameter only slightly smaller than the diameter of the guide hole. A hole may be drilled in the end face of one workpiece first of all in the manner disclosed hereinbefore, using a drill jig constructed as specified. The workpiece may then be so applied to that surface of the jig member which has the pin-receiving bore that the head of the pin extends into the bore produced, one main surface of the workpiece being in alignment with the flat outer side of the jig member. In this position the other workpiece may be so applied to the workpiece in engagement with the head of the pin and the flat outer side of the jig member that the guide hole is situated at the place at which a hole is to be drilled into the side face of the workpiece. When the side-face hole is produced in this way, the result is that the holes or bores produced in the workpieces lie in a common plane, namely in the plane in which the longitudinal axes of the guide hole, guide bore and pin-receiving bore are also disposed. Another embodiment further comprises a flat, outer side of the jig member which is parallel with the positioning zone and extends at right angles to the longitudinal axis of said at least one guide hole, a zone of the jig member extending normally of said guide bore, at least one pin-receiving slot having a semi-circular slot bottom, said slot extending through a zone of the jig member through which the guide bore extends, said pin-receiving slot having a longidutinal axis which extends through the centre of the semicircle of the slot bottom and parallel with the longitudinal axis of the guide bore, said longitudinal axis of the slot lying in the plane of the longitudinal axes of guide hole and guide bore, the distance of said slot from the outer side of the jig member being equal to the distance between the bearing surface and the guide hole, and the radius of the semicircle slot bottom is equal to or slightly greater than the radius of the guide hole. If such pin-receiving slots are used, the previously mentioned pin to be inserted in the pin-receiving bore is no longer necessary, but is replaced by a dowel which is to be used to interconnect the two workpieces and which is inserted, with a suitable arrangement in relation to the jig member, into the bottom of the pin-receiving slot. Embodiments of the invention will now be described in greater detail by using by way of example only, with reference to the embodiments shown in the accompanying drawings, in which: Fig. 1 is a section through a drill jig; Fig. 2 is a side elevation of a drill jig similar to that shown in Fig. 1; Fig. 3 is a plan view of the drill jig shown in Fig. 2; Fig. 4 is a view of the drill jig of Fig. 2 viewed from the left, the screw clamp being omitted; Fig. 5 is a section taken along the line V-V in Fig. 4; and, Fig. 6 is a section through another embodiment of the drill jig. Referring to Fig. 1, a drill jig comprises a jig member 1 having a top arm 3, a central portion 2 and a bottom arm 4. A lining bush 9 of hardened material is inserted in the arms in order to bound a continuously extending guide bore 8. A flat positioning zone 10 extends on the underside of the arm 3 at a distance from the longitudinal axis of the guide bore 8 and parallel therewith. A lining bush 6 also of hardened material, is inserted in the central portion of the drill jig 2 in order to bound a continuously extending guide hole 5 whose diameter is equal to the diameter of the guide hole 8. On the inner side of the central portion 2 and adjacent the arm 3 is formed a bearing surface 7 which extends parallel with the longitudinal axis of the guide hole 5 and co-operates with the positioning zone 10 to enclose a right angle. It is a decisive feature that the distance between the bearing surface 7 and the longitudinal axis of the guide hole 5 is equal to the distance between the positioning zone 10 and the longitudinal axis of the guide bore 8. The arm 4 is formed with a screwthreaded bore (not shown) into which is screwed the shank 14 of a spindle screw. Shank 14 has a gripping head 15 and a clamping member 16, the latter lies between the arm 4 and the bearing surface 7. The upper surface of the jig member 1, extending at right angles to the outer surface 11, is formed with a screwthreaded bore 12 into which a pin 13 is screwed. The head of pin 13, which is formed with a slot for receiving a screwdriver, has a diameter which is equal to or slightly smaller than the diameter of the guide hole 5. The distance of the longitudinal axis of the screwthreaded bore 12 from the outer surface 11 is equal to the distance of the longitudinal axis of the guide hole 5 from the bearing surface 7. The drill jig illustrated may be used to drill holes in two workpieces, for example, two timber boards, to enable the two workpieces to be interconnected at right angles by means of dowels. When so connected, the end face of one workpiece is in alignment with the outer surface of the other workpiece arranged at right angles thereto. For this purpose, the workpieces are moved into a position in relation to one another such as is shown for the workpieces 50 and 52 in Fig. 1. In this position the workpieces 50 and 52 may be pressed together by screw clamps (not shown) for secure positioning. As shown the bearing surface 7 lies on the upper surface zone of the workpiece 50. Workpiece 50 projects beyond the adjacent end face of the workpiece 52. The workpiece 52 lies on the workpiece 50 and its end face abuts the positioning zone 10. In this position, holes 51 and 53 are drilled through the guide hole 5 and the guide bore 8 in the workpieces 50 and 52. The drilled holes have substantially the same diameter as the guide hole 5. The hole 53 lies at the same distance from the end face of the workpiece 52 bearing against the positioning zone 10, as the hole 51 lies from the surface of the workpiece 50 bearing against the bearing surface 7. The holes 51 and 53 also lie in a common plane. In this manner, a number of spaced out holes may be made in the workpieces 50 and 52, which are interconnected by clamping. Then, after the workpieces 50 and 52 have been separated, dowels can be inserted in the holes 53 in the workpiece 52. The dowels project from the holes 53. The workpiece 50 with the holes 51 is then placed on to such dowels. For this purpose the workpiece 50 is so positioned on the workpiece 52 that the surface of the workpiece 50 bearing against the bearing surface 7 (Fig. 1) is in alignment with the end face of the workpiece 52 bearing against the positioning zone 10 (Fig. 1). It may be required that the connection between the workpiece 50 and the workpiece 52 is not to be performed in such a way that one end face of the workpiece 52 is in alignment with one outer surface of the workpiece 50, i.e. unlike the arrangement of the holes 51 and 53 shown in Fig. 1. Instead it may be that the workpiece 50 is to be attached to the workpiece 52 at a fairly large distance from the end face bearing against the positioning zone 10 (Fig. 1). The latter arrangement may be achieved by means of the pin 13. For this purpose the workpiece 50 is first caused to bear against the bearing surface 7 in the manner illustrated in Fig. 1, and the hole 51 is drilled. After such hole or several such holes have been drilled in the workpiece 50, the workpiece 50 is so placed on the upper surface of the drill jig 1 (Fig. 1) that the pin 13 extends into the hole 51. This ensures that the surface of the workpiece 50, which previously bore against the bearing surface 7, is now in alignment with the flat outer side 11 of the jig member. In this position the workpiece 52 may be brought to bear against the workpiece 50 and against the outer side 11 of the jig member 1. It is then so positioned that the guide hole 5 is at the place at which a dowel is to be inserted. Thereafter on connection of the workpiece 52 to the workpiece 50, the dowel extends into the hole 51 into which the pin 13 extends. In this position of the workpiece 52, the corresponding hole 53 (Fig. 1) is drilled from the right through the guide hole 5. This procedure ensures that each of the holes 51 and 53, which are to receive a dowel, lies in a common plane whereby the connection is made without difficulty. The drill jig shown in Figs. 2 to 5 corresponds in functional principle to the drill jig shown in Fig. 1. For this reason like members have like references, but with the addition of 100. In what follows, basically only the differences from the drill jig in Fig. 1 will be described. The drill jig shown in Figs. 2 to 5 is suitable for the drilling of holes of difference diameters: the guide hole 135 and guide bore 138 having the smallest diameter, the guide hole 125 and the guide bore 128 having the largest diameter, and the guide hole 105 and the guide bore 108 having a middle diameter. The distance from the bearing surface 107 and the positioning zone 110 also differs in accordance with their diameters. However, the guide holes and guide bores also have insert bushes of hardened material. The only bushes shown in Fig. 5 are the bushes 126 and 129 for the guide hole 125 and the guide bore 128. The bearing surface 107 and the positioning zone 110 are formed by four parallel, rib-shaped projections 120, 121, 122 and 123 which merge into a step-shaped wall 137 (Fig. 5) of the jig member 101. A cavity is disposed between the step-shaped wall 137, the outer side 111, the top horizontal wall (Fig. 5) of the jig member 101 and the end walls, one of which is shown in Fig. 2. The upper horizontal wall is formed with pin-receiving slots 130, 132 and 134, so that the cavity is accessible through such slots. As shown in Fig. 3, the bottom of these pin-receiving slots is semicircular, the centres 131, 133, 135 of such semicircles lying in the same plane as the longitudinal axis of the guide bore 102, 128; 138 (cf. Fig. 3) and the longitudinal axis of the guide hole 105, 125; 135. The distance of the particular centre of the semicircle from the outer surface 111 is equal to the distance of the associated guide hole 105, 125 or 135 from the bearing surface 107. The drill jig shown in Figs. 2 to 5 may be used in the same manner as the drill jig shown in Fig.l for drilling holes in two workpieces, these holes corresponding to the holes 51 and 53 in the workpieces 50 and 52 shown in Fig. 1. Pin-receiving slots 130, 132 and 134 are provided instead of one or more screwthreaded bores 12 (Fig. 1). The slots have the same function as the screwthreaded bores 12 in Fig. 1. One or more end-face bores are made in a workpiece, corresponding to the bore 51 in Fig.1. The dowels to be used for the subsequent connection are then inserted in such bores. The particular dowel so inserted, is introduced into the corresponding pin-receiving slot for the positioning of the workpiece and brought into engagement with the slot bottom. The surface of the workpiece formerly bearing against the bearing surface 107 for the drilling of the holes, is now in alignment with the flat outer side 111. Then the bores are made in the other workpiece in the same manner, as described in connection with the use of the screwthreaded bore 12 and the pin 13 in Fig. 1. The drill jig shown in Fig. 6 differs from those shown in Fig. 1 and Figs. 2 to 5 in respect of the location of the positioning zone and the bearing surface on the jig member. However, since otherwise it is similar to the drill jig shown in Fig. 1, like members have given like references with the addition of 200. The jig member 201 of the drill jig shown in Fig 6 is substantially U-shaped and has an upper arm 203, a lower arm 204 and a central portion 202. A guide bore 208 which is bound by aligning bush 209, extends through the top arm 203. A guide hole 205, which is bound by aligning bush 206, extends through the central portion 202. The longitudinal axes of such bores extend perpendicular to one another in a common plane. A flat bearing surface 207 is arranged parallel with the longitudinal axis of the guide hole 205 and extends on the underside of the arm 203 between its free end and the boundary of the guide bore 208 adjacent thereto. A positioning zone 210 is aligned to be parallel with the longitudinal axis of the guide bore 208 and is disposed on the inner side of the central portion 202. This positioning zone extends between the arm 204 and the boundary of the guide hole 205 adjacent thereto. In this case also the distance between the longitudinal axis of the guide bore 208 and the positioning zone 210 is equal to the distance between the longitudinal axis of the guide hole 205 and the bearing surface 207.. In the transitional zone between the arm 203 and the central portion 202 but outside the zone of the guide hole 205 the guide bore 208, are disposed stops 236 which extend from the central portion 202 beyond the opposite boundary of the guide bore 208. A shank 214 of a screw clamp is inserted in a screwthreaded bore of the bottom arm 204. This screwthreaded bore corresponds to screwthreaded bore 117 in Fig. 5. The shank 214 has a gripping head 215 and a clamping member 216. The procedure for drilling holes into two workpieces, corresponding to the holes 51 and 53 in the workpieces 50 and 52 in Fig. 12 is as follows. The workpiece 250, which is to be drilled at its end face, is caused to bear against the bearing surface 207. The stops 236 prevent the workpiece 250 from moving into the zone of the guide bore 208. The other workpiece 252, which bears against the lower surface of the workpiece 250 as viewed in Fig. 6, is caused to bear against the positioning zone 210. In this position the two workpieces 250 and 252 may be rigidly interconnected by screw clamps (not shown). In this context, the screw clamp 214 extending through the arm 204 merely attaches the drill jig to the workpieces 250, 252. In this position the holes 251 and 253 can be made by drills guide by the guide hole 205 and the guide bore 208. This ensures that the holes 251 and 253 lie in a common plane and have the same diameter. After all the holes 251 and 253 have been made, the drill jig is removed, and the screw clamps holding the workpieces 250 and 252 together are loosened. The required dowels are inserted into the holes 253, and the workpiece 250 must then be merely pivoted through 900 anticlockwise (Fig. 6) to bring the holes 251 into engagement with the dowels in the holes 253. In this position the end face of the workpiece 250, which was previously bearing against the positioning zone 210, is in alignment with that surface of the workpiece 250 which was previously bearing against the bearing surface 207.

Claims: CLAIMS 1. A drill jig for preparing dowel joints between two workpieces to be interconnected end-face to side-face, comprising a jig member (1, 101, 201) having a bearing surface (7, 107, 127) for the workpiece (50, 150, 250) which is to be drilled at its end face, at least one guide hole (5, 105. 205) extending parallel to the bearing surface (7, 107, 207), a positioning zone (10, 110, 210) extending perpendicularly to the bearing surface (7, 107, 207) and against which positioning zone (10, 110, 210) abuts in use the end face of the workpiece (52, 152, 252) which is to be drilled on its side face, at least one guide bore (8, 108, 208) extending parallel with the positioning zone (10, 110, 210), the longitudinal axes of said guide base (8, 108, 128) and said guide hole (7, 107, 207) extending perpendicular to one another in the same plane, the distance between said axis of said guide bore (8, 108, 208) and said positioning zone (10, 110, 210) being equal to the distance between said axis of said guide hole (5, 105, 205) and said bearing surface (7, 107, 207), characterized in that the bearing surface (7, 107, 207) and the positioning zone (10, 110, 210) lie completely inside or completely outside the right angle enclosed by said longitudinal axes of the guide hole (5, 105, 205) and the guide bore (8, 108, 128). 2. A drill jig as claimed in Claim 1, wherein the positioning zone (10, 110) and the bearing surface (7, 107) lie completely inside the right angle enclosed by the longitudinal axes of the guide hole (5, 105) and the guide bore (8, 108, 208) and wherein said guide hole (5, 105) extends through an inner surface at right angles to said bearing surface (7, 107), said bearing surface (7; 107) lies between said inner surface and the positioning zone (10; 110), and the positioning zone (10; 110) terminates at that surface of the jig member (1; 101) through which the guide bore (8; 108, 128 138) extends. 3. A drill jig as claimed in Claim 1, wherein the positioning zone (210) and the bearing surface (207) lie completely outside the right angle enclosed by the longitudinal axes of the guide hole (205) and the guide bore (208), and wherein said guide hole (205) extends through an inner surface at right angles to said bearing surface (207), and the positioning zone (210) is formed by said inner surface, and the bearing surface (207) is formed by that surface of the jig member (201) -through which the guide bore (208) extends. 4. A drill jig as claimed in Claim 3, wherein stops (236) are disposed outside the zone of the guide bore (208) and adjacent that surface of the jig member (201) through which the guide bore (208) extends, and said stops (236) extend to beyond the side of the guide bore (208) remote from said inner surface. 5. A drill jig as claimed in any one of Claims 1 to 4, wherein an arm (4) of the jig member is arranged opposite a zone (3) of the jig member, said zone (3) defining said at least one guide bore (8), and a clamping screw (14, 15, 16) is arranged with its clamping end (16) extending out of the arm (4) on the side adjacent the guide bore (8). 6. A drill jig as claimed in any one of Claims 1 to 5, wherein a flat outer side (11; 211) of the jig member (1; 201) is parallel with the positioning zone (10, 210) and extends at right angles to the longitudinal axis of said at least one guide hole (5; 205), and a pin-receiving bore (12; 212) is provided in the outside of that zone of the jig member (1; 201) which has at least one guide bore (8; 208), said pin-receiving bore (12; 212) extending parallel with the guide bore (8; 208) with its longitudinal axis lying in the plane of the longitudinal axes of guide hole (5; 205) and guide bore (8; 208), the distance of said pin-receiving bore (12, 212) from the outer side (11; 211) of the jig member (1; 201) is equal to the distance between the bearing surface (7; 207) and the guide hole (5; 205). 7. A drill jig as claimed in Claim 6, further comprising a pin (13; 213) for insertion in the pin-receiving bore (12; 212), wherein said pin (13, 213) has a head which has a diameter only slightly smaller than the diameter of the guide hole (5; 205). 8. A drill jig as claimed in any one of Claims 1 to 5, wherein a flat outer side (111) of the jig member (101) is parallel with the positioning zone (110) and extends at right angles to the longitudinal axis of said at least one guide hole (105, 125, 135) a zone (103) of the jig member (101) extending normally of said guide bore (108, 128, 138), at least one pin-receiving slot (130, 132, 134) having a semi-circular slot bottom and being located in the outside of said zone (103) said pin-receiving slot (130, 132, 134) having a longitudinal axis which extends through the centre (131, 132, 134) of the semi-circle of the slot bottom and parallel with the longitudinal axis of the guide bore (108; 128; 138), the said longitudinal axis of said slot (130, 132, 134) lying in the plane of the longitudinal axes of guide hole (105; 125; 135) and the guide bore (108; 128; 138), the distance of said slot (130, 132, 134) from the outer side (111) of the jig member (101) being equal to the distance between the bearing surface (107) and the guide hole (105; 125; 135), the radius of said semicircle slot bottom being equal to or slightly greater than the radius of the guide hole (105; 125; 135).

Inventors: MARX, DIETRICH
Applicants: BLACK & DECKER INC.
Application year: 1984
Main classification: B27C3
IPC codes: B23B47