GB2217241A - Drill router and chuck therefor - Google Patents

Abstract

The drill router 15 has a drill portion 30 with drill flutes 31, 32 a router portions 33 extending from said drill portion 30 part-way along the flutes, the remainder of the tool comprising a non-fluted shank portion 39 having a pair of flats 41, 42 defined therein, a first flat 41 being aligned with a drill flute face and a second flat 42 being disposed at substantially right angles thereto. A chuck has screws 51, 52 for engaging the flats 41, 42 and the tool axial position is set by a screw 50. The chuck nose end is tapered concavely to align with the flutes for swarf removal. <IMAGE>

Description

Title: Drill Router The present invention relates to a cutting tool for drilling and routing. In particular the present invention relates to a cutting tool for the drilling and routing of workpieces comprising stacks of thin sheets of material.

Previously proposed drill-router designs comprise a machine tool having a rotary bit therein. The tool is traversed into a workpiece comprising a stack of thin sheets of material such as aluminium which are drilled through completely. The tool is then moved laterally with respect to the workpiece so as to form slots or aperture by a routing or milling action, the tool being moved so as to cut shapes from the sheets.

However, where the workpiece comprises a stack of thin sheets of material which distort or break easily, problems have been encountered in distortion of the workpiece due to the pressure used during the drilling step and vibration of the tool causing fretting and degradation of surface finish.

It is an object of the present invention to provide a drill-router in which the problems identified above are obviated or mitigated such that the tool rotational speed can be increased without reduction in finish quality.

In accordance with the present invention, there is provided a rotary tool comprising a drill portion including drill flute formations, a router portion extending from said drill portion part-way along said tool, the remainder of the tool comprising a non-fluted shank portion having a pair of flats defined therein, a first flat being aligned with a drill flute face a second flat being disposed at substantially right angles to said first.

Preferably, the non fluted shank portion is generally cylindrical and conveniently includes complete cylindrical surfaces disposed on either side of the pair of flats to act as register sections of the tool.

It is particularly preferred that the plane of each flat is angled relative to the axis of the bit, typically such that the plane diverges from the axis as the distance from the fluted portion increases. A typical degree of 0 divergence is 1-5 The drilling and routing geometry of the bit is conveniently arranged to allow optimum penetration of material with as little pressure as possible. To achieve this for the drilling operation, the chisel point is about 5-15%, preferably about 10% calculated relative to the outside diameter of the bit. The web of the drill portion is also arranged to be about 10% -30% calculated on the same basis. The angle and length of the drill flutes are preferably such that the drill point has penetrated a first sheet of material and has begun to drill the next sheet in a stack before the begining of the routing portion or tool diameter is engaged.

To reduce burring, the transition from a drilling flute to a routing flute i.e. the tool diameter is radiussed over 10% of the total diameter.

The outer diameter of each routing flute peak is typically radially relieved to form a curved surface.

The tool is normally located in an axial bore in a chuck, a pair of radial locating screws being provided which can project into the bore and bear against a respective flat.

The locking screws are typically arranged to be perpendicular to the flats.

It is also preferred that an axial positioning screw is provided which can be used to ensure that an appropriate length of tool projects from the chuck.

The end of the chuck is conveniently relieved so as to reduce in outside diameter toward the end from which the tool projects. It is particularly preferred that the chuck end is curved so as to correspond with the curve of the routing flutes and so direct chips away from the tool and workpiece.

The present invention will now be described by way of example, with reference to the accompanying drawing in which: Figure 1 is a sectional view of a tool for use in a machine tool as shown in Figure 1; Figure 2 is a perspective view of a tool for use in a machine tool as shown in Figure 1; Figure 3 is an end view on arrow A of the tool shown in Figure 2; Figure 4 is a detailed view of the portion X of Figure 2; Figure 5 is a detailed view of the portion Y of Figure 2, and Figure 6 is a part sectional side view of a chuck for use in a machine tool as shown in Figure 1.

Referring to Figure 1, machine tool shown therein comprises a spindle (not shown) on which a chuck of generally circular cross section indicated by reference numeral 11, can be rotatably mounted. A tool change flange 12 is provided around the chuck 11 such that the chuck 11 can be automatically changed by an appropriate mechanism (if present). A cylindrical portion 13 extends beyond the flange 12 and is provided with a concentric bore 14 for locating a tool 15. The tool 15 is retained in the bore 14 by means of a pair of lateral grub screws, which bear upon flats (not shown) provided on the shank of the tool 15. Further aspects of the chuck 11 and the tool 15 will be described in detail below.

The free end 18 of the cylindrical portion 13 is tapered and curved radially inwardly to the point at which the tool 15 projects from the chuck 11. The taper is concavely curved and corresponds in curvature to the curve defined by flutes in the tool 15.

A nose piece 21 is provided between the chuck 11 and a workpiece 27. The nose piece 21 comprises an end plate 22 adjacent to the free end 18 of the chuck 11. An aperture 23 is provided in the end plate 22 through which the bit 15 can project. The end plate 22 is provided with a rebate 24 around the aperture 23 and the curved portion 18 and the rebated plate 22 together define an annular channel 25 which surrounds the aperture 23. The channel 25 communicates with a side passage 26 in the nose piece 21, which opens from the side thereof.

Referring to Figures 2-5, the tool shown therein comprises an elongate body which is generally cylindrical. One end 30 of the body is formed as a drill point having a pair of o flutes 31, 32. The point angle is approximately 120 0 o 140 the chisel point is approximately 10% of the outer diameter of the body, this small point ensuring that little pressure is required to drill so avoiding distortion of soft workpieces such as aluminium and delamination of materials such as kevlar.

The portion of the body extending from the end 30 is formed as a router section 33, the routing flutes 34, 35 being formed as continuations of the drilling flutes 31, 32. The transition from a drilling flute to a routing flute is effected gradually at a radiussed edge 36 over approximately 10% of the outer diameter of the body.

This blending of the two types of flute reduces burring.

The web diameter of the tool is typically 40-60% of the outside diameter which is generally 3-12mm. Typical rotational speeds are 6000 - 30000 rpm. The cutting edges 37 of the routing flutes 34, 35 are radially relieved to form a curved surface 38.

The router section 33 terminates part way along the body, the remainder of which comprises a generally cylindrical shank portion 39. The free end 40 of the shank portion 39 is chamfered slightly to form a lead-in. A pair of elongate flats 41, 42 are formed in the shank portion 39.

The plane of each flat 41, 42 is arranged so as to diverge o from the axis of the body by about 1-5 toward the free end 40. One of the flats , 41 is aligned with a cutting face of one of the drill flutes 31, 32, the plane of the other flat 42 being arranged substantially perpendicular thereto. The flats 41, 42 terminate short of both the free end 40 and the end of the router section 33 leaving cyl-indrical register portions 43,44 at both ends of the shank portion 39.

Referring now to Figure 6, the chuck shown therein is substantially as described in relation to Figure 1 above.

The bore 14 terminates short of the upper end of the chuck and an adjusting screw 50 is provided in this region so as to allow adjustment of the overall reach of the tool in the bore 14. A pair of threaded bores 51, 52 for locating screws (not shown) are provided in the cylindrical portion 13 opening into the bore 14. The bores 51, 52 are arranged substantially at right angles to each other and o the axis of each bore 51, 52 is approximately 1-5 from the radial plane. In order that the shank 39 of the bit 15 can be inserted into the bore 14 a small clearance must remain this clearance being the cause of certain vibrations in other designs. In the present case, the shank 39 is inserted into the bore 14 and the adjusting screw 50 adjusted until a predetermined length of bit projects from the chuck 11.The tool is arranged so that the flats 41, 42 align with the bores 51, 52 and the locating screws are tightened so as to fix the position of the tool. The provision of the two flats 41, 42 and the corresponding locating screws in the chuck reduces the vibration of the tool due to the clearance mentioned above. The provision of the adjusting screw 50 means that bits can be used after re-servicing without detriment to the performance of the machine tool.

In use, the machine tool is traversed gently onto the workpiece 27 which typically comprises a stack of sheets of aluminium or kevlar often up to 10mum thick. The drill point penetrates the workpiece, the next sheet in the stack being drilled before the drill diameter has completely passed through the previous sheet. The swarf and chips are drawn up the flutes in the bit, through the aperture 23 into the channel 25 from which they are removed via the passage 26. Because the tapered section corresponds to the curve of the bit flutes, the swarf is easily removed with reduced possibility of clogging.

The chuck is thus able to support a greater length of bit than would be normally possible and so further reduces vibration problems.

Claims (1)

1. Claims:

   1. A rotary tool comprising a drill portion including drill flute formations, a router portion extending from said drill portion part-way along said tool, the remainder of the tool comprising a non-fluted shank portion having a pair of flats defined therein, a first flat being aligned with a drill flute face and a second flat being disposed at substantially right angles to said first.

   2. A tool as claimed in claim 1, wherein the non-fluted shank portion is generally cylindrical and includes complete cylindrical surfaces disposed either side of the pair of flats.

   3. A tool as claimed in claim 1 or 2, wherein the plane of each flat is angled relative to the axis of the bit, such o that the plane diverges by 1-5 from the axis as the distance from the fluted portion increases.

   4. A tool as claimed in any preceding claim, wherein the chisel point of the drill portion is 5-15% calculated relative to the outside diameter of the bit and the web of the drill portion is 10%-30% calculated on the same basis.

   5. A tool as claimed in any preceding claim, wherein the transition from a drilling flute to a routing flute is radiussed over 10% of the total tool diameter.

   6. A rotary machine tool in which a tool as defined in any preceding claim is located in an axial bore in a chuck, a pair of radial locating screws being provided which can project into the bore and bear against a respective flat on the tool.

   8. A machine tool as claimed in claim 7, wherein the locking screws are arranged to be perpendicular to the flats.

   9. A machine tool as claimed in claim 7 or 8, wherein an axial positioning screw is provided to determine the length of tool projecting from the chuck.

   10. A machine tool as claimed in claim 7, 8 or 9 wherein the end of the chuck is relieved so as to reduce in outside diameter toward the end from which the tool projects.

   11. A machine tool as claimed in claim 10, wherein the chuck end is curved so as to correspond with the curve of the routing flutes on the tool.

   12. A rotary tool which is substantially as herein described in relation to the drawings.

   13. A rotary machine tool which is substantially as herein described in relation to the drawings.