GB2067440A

GB2067440A - Combined screw tap and drill

Info

Publication number: GB2067440A
Application number: GB8010214A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-12-31
Filing date: 1980-03-26
Publication date: 1981-07-30

Abstract

A rotary tool comprises a unitary, elongate, rod-form member. The member is formed in one length region as a drill 12 for drilling a hole and is formed in its other length region as a screw tap 13 for tapping a hole. The member is adapted to be held by a machine for rotating the member about the common axis of the two length regions thereby to effect the drilling and tapping. <IMAGE>

Description

SPECIFICATION Combined screw tap and drill This invention relates to improved tools for tapping.

Tapping is conventionally carried out by first drilling a hole in the workpiece and then tapping the hole, i.e. providing the hole with internal screwthreads, with a separate screw tap. This conventional method has a number of disadvantages. For example, it involves use of separate tools for drilling and tapping causing inconvenience to the person carrying out the operation. Moreover, the operation of tapping the hole may result in the tapped hole not being coaxial with the drilled hole, since the external diameter of the screw tap is larger than the diameter of the previously drilled hole and therefore there is a tendency for the screw tap to wander. Use of two separate tools in the conventional tapping method is also time consuming.

According to the present invention there is provided a rotary tool comprising a unitary, elongate, rod-form member having two coaxial length regions, the member being formed in one length region as a drill for drilling a hole and being formed in its other length region as a screw tap for tapping a hole, said member being adapted to be held by a machine for rotating the member about the common axis of the two length regions thereby to effect said drilling and tapping.

For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawing in which: Figures 1, 2, 3, and 4 show elevational views of respective rotary tools.

The tools illustrated in Figures 1 to 3 each comprise a unitary, elongate, rod-form member which is formed at its upper end (the left end seen in the drawing) to be held in the chuck of a drilling machine and is formed at its lower end (the right end) as a drill 12. Intermediate its ends, the rod-form member is formed as a spiral tap 13. The diameter of the spiral tap 13 is slightly larger than that of the drill 12. When the tool is fitted in a drilling machine, drilling and tapping can be carried out without any need to change tools, although it is of course to reduce the speed of rotation of the tool for tapping. If the workpiece and the drilling machine are fixed relative to one another against movement perpendiocular to the common axis of the drill and the spiral tap, the central axis of the tapped hole will necessarily coincide with the central axis of the drilled hole.

The drill itself assists in achieving this coaxial relationship, since it guides the spiral tap into the hole. This leads to improved precision.

The chip capacity of the tool is as high as that of a conventional drill or screw tap, because the flutes of both the drill and the tap are available to accommodate chips. Figure 1 shows a tool in which the drill and the tap have the same number of flutes, and in this case the flutes of the tap are arranged as continuations of the flutes of the drill. In the case of Figure 2, on the other hand, the tap has more flutes than the drill and therefore an intermediate region 14 of reduced diameter is provided between the drill and tap to facilitate discharge of chips and prevent jamming of the tool. In the case of Figure 3, there is provided between the region 14 and the leading end of the screw tap 13 a fluted region 15 in order to improve chip capacity. The flutes of the region 15 constitute prolongations of the flutes of the tap 13.

It is of course necessary that the minimum diameter of an internal thread tapped using the screw tap be at least as large as the diameter of a hole formed using the drill, since otherwise parts of the screw tap will not enter into cutting engagement with the workpiece when the hole is tapped. Normally, the diameter of the tap is 1/16 as large again as the diameter of the drill.

Figure 4 illustrates a tool in which the screw tap 13 and the drill 12 are provided at opposite ends of the rod-form member, which in use is gripped in the chuck of the drilling machine at the intermediate region 16. This of course requires that the chuck should have a deep socket and that the gripping ends of the jaws of the chuck should be set inwardly from other parts of the jaws in order to avoid damaging the chuck or that part of the tool which is in the chuck socket. Provided the workpiece and the drilling machine are fixed against relative movement perpendicular to the axis of rotation of the chuck, the axis of the tapped hole will coincide with the axis of the drilled hole even though the tool has to be removed from the chuck and reversed after drilling in order to carry out the tapping operations.In the case of the Figure 4 tool, there is no required relationship between the diameter of the drill and that of the tap, although the relationship of the Figure 1 to 3 tools will normally obtain.

The tool may be manufactured by integral molding, machining or welding to combine a drill and a screw tap having the same respective numbers of flutes. Where the tool is constructed as shown in Figure 2 or 3, with the drill and the tap having different respective numbers of flutes, an appropriate section of smaller diameter is provided at the rear end of the drill before the drill and the tap are combined.

The invention is not restricted to the particular tool described and illustrated; since it will be apparent to those skilled in the art that variations may be made without departing from the invention as defined in the appended claims. For example, it is not necessary that the screw tap and the drill be of the spiral type, since other types of screw tap and drill can be used depending upon the requirements of the particular task to be performed. In particular any type of tap other than a hand tap may be used.

1. A rotary tool comprising a unitary, elongate, rod-form member having two coaxial length regions, the member being formed in one length region as a drill for drilling a hole and being formed in its other length region as a screw tap for tapping a hole, said member being adapted to be held by a machine for rotating the member about the common axis of the length regions thereby to effect said

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Combined screw tap and drill This invention relates to improved tools for tapping. Tapping is conventionally carried out by first drilling a hole in the workpiece and then tapping the hole, i.e. providing the hole with internal screwthreads, with a separate screw tap. This conventional method has a number of disadvantages. For example, it involves use of separate tools for drilling and tapping causing inconvenience to the person carrying out the operation. Moreover, the operation of tapping the hole may result in the tapped hole not being coaxial with the drilled hole, since the external diameter of the screw tap is larger than the diameter of the previously drilled hole and therefore there is a tendency for the screw tap to wander. Use of two separate tools in the conventional tapping method is also time consuming. According to the present invention there is provided a rotary tool comprising a unitary, elongate, rod-form member having two coaxial length regions, the member being formed in one length region as a drill for drilling a hole and being formed in its other length region as a screw tap for tapping a hole, said member being adapted to be held by a machine for rotating the member about the common axis of the two length regions thereby to effect said drilling and tapping. For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawing in which: Figures 1, 2, 3, and 4 show elevational views of respective rotary tools. The tools illustrated in Figures 1 to 3 each comprise a unitary, elongate, rod-form member which is formed at its upper end (the left end seen in the drawing) to be held in the chuck of a drilling machine and is formed at its lower end (the right end) as a drill 12. Intermediate its ends, the rod-form member is formed as a spiral tap 13. The diameter of the spiral tap 13 is slightly larger than that of the drill 12. When the tool is fitted in a drilling machine, drilling and tapping can be carried out without any need to change tools, although it is of course to reduce the speed of rotation of the tool for tapping. If the workpiece and the drilling machine are fixed relative to one another against movement perpendiocular to the common axis of the drill and the spiral tap, the central axis of the tapped hole will necessarily coincide with the central axis of the drilled hole. The drill itself assists in achieving this coaxial relationship, since it guides the spiral tap into the hole. This leads to improved precision. The chip capacity of the tool is as high as that of a conventional drill or screw tap, because the flutes of both the drill and the tap are available to accommodate chips. Figure 1 shows a tool in which the drill and the tap have the same number of flutes, and in this case the flutes of the tap are arranged as continuations of the flutes of the drill. In the case of Figure 2, on the other hand, the tap has more flutes than the drill and therefore an intermediate region 14 of reduced diameter is provided between the drill and tap to facilitate discharge of chips and prevent jamming of the tool. In the case of Figure 3, there is provided between the region 14 and the leading end of the screw tap 13 a fluted region 15 in order to improve chip capacity. The flutes of the region 15 constitute prolongations of the flutes of the tap 13. It is of course necessary that the minimum diameter of an internal thread tapped using the screw tap be at least as large as the diameter of a hole formed using the drill, since otherwise parts of the screw tap will not enter into cutting engagement with the workpiece when the hole is tapped. Normally, the diameter of the tap is 1/16 as large again as the diameter of the drill. Figure 4 illustrates a tool in which the screw tap 13 and the drill 12 are provided at opposite ends of the rod-form member, which in use is gripped in the chuck of the drilling machine at the intermediate region 16. This of course requires that the chuck should have a deep socket and that the gripping ends of the jaws of the chuck should be set inwardly from other parts of the jaws in order to avoid damaging the chuck or that part of the tool which is in the chuck socket. Provided the workpiece and the drilling machine are fixed against relative movement perpendicular to the axis of rotation of the chuck, the axis of the tapped hole will coincide with the axis of the drilled hole even though the tool has to be removed from the chuck and reversed after drilling in order to carry out the tapping operations.In the case of the Figure 4 tool, there is no required relationship between the diameter of the drill and that of the tap, although the relationship of the Figure 1 to 3 tools will normally obtain. The tool may be manufactured by integral molding, machining or welding to combine a drill and a screw tap having the same respective numbers of flutes. Where the tool is constructed as shown in Figure 2 or 3, with the drill and the tap having different respective numbers of flutes, an appropriate section of smaller diameter is provided at the rear end of the drill before the drill and the tap are combined. The invention is not restricted to the particular tool described and illustrated; since it will be apparent to those skilled in the art that variations may be made without departing from the invention as defined in the appended claims. For example, it is not necessary that the screw tap and the drill be of the spiral type, since other types of screw tap and drill can be used depending upon the requirements of the particular task to be performed. In particular any type of tap other than a hand tap may be used. CLAIMS

1. A rotary tool comprising a unitary, elongate, rod-form member having two coaxial length regions, the member being formed in one length region as a drill for drilling a hole and being formed in its other length region as a screw tap for tapping a hole, said member being adapted to be held by a machine for rotating the member about the common axis of the length regions thereby to effect said drilling and tapping.

2. A rotary tool as claimed in claim 1, wherein the member has two opposite end regions and an intermediate region therebetween, one of said end regions constituting said one length region, the intermediate region constituting said other length region, and the other end region being coaxial with said one end region and being adapted to be gripped in a chuck of a drilling machine for rotating the member about said common axis.

3. A rotary tool as claimed in claim 1 or claim 2, wherein the screw tap is a spiral screw tap.

4. A rotary tool as claimed in claim 2, wherein the rod-form member has a length region of reduced diameter between said one length region and said other length region.

5. A rotary tool as claimed in claim 4, wherein the rod-form member has a fluted length region between said other length region and said length region of reduced diameter, said fluted length region being without cutting edges.

6. A rotary tool substantially as hereinbefore described with reference to Figure 1 or Figure 2 or Figure 3 or Figure 4 of the accompanying drawings.