GB2490955A

GB2490955A - Hole finishing tool

Info

Publication number: GB2490955A
Application number: GB1108466.2A
Authority: GB
Inventors: Croy John Grossart; Gordon Ramsay
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 2011-05-20
Filing date: 2011-05-20
Publication date: 2012-11-21
Also published as: GB201108466D0

Abstract

The tool 10 for finishing a hole (2, Figure 4) in a work piece (1, Figure 4) includes a neck portion 16 having an axial length and a first portion 14 and a second portion 18 disposed either side of the neck portion. The first and second portions have first and second inclined finishing portions, 22 and 26 respectively, inclined inwardly towards the neck portion in opposing directions. The tool is arranged such that it can be disposed within the hole and simultaneously rotated and moved in a circular path so as to finish an edge of the hole with one of the finishing portions. The inclined portions may include at least part of a frusto-conical finishing surface. The tool may also include helical swarf passageways (28, Figure 3). The tool may be a deburring tool and may be used for finishing a blind hole in addition.

Description

HOLE FINISHING TOOL

The present invention relates to a tool for finishing holes, in particular, a tool for finishing through-holes or blind-holes in a workpiece.

When manufacturing a component, through-holes and blind-holes may be machined in a workpiece. The machining of the hole may result in an upper and/or lower edge having a burr. It is desirable and often necessary to remove this burr and deburring tools exist for finishing burred edges.

One known type of deburring tool is a countersink tool comprising a shaft and a conically shaped cutting bit which tapers towards the distal end of the tool. In order to remove the burr, the tip of the conically shaped cutting bit is located within the hole opening and the tool is rotated. This removes the burr by applying a chamfer to the edge. Such a countersink tool can also be used to create a lead-in angle for tapped holes.

While the above described tool is suitable for some applications, there are a number of disadvantages associated with it. For example, if it is necessary to remove a deburr from an upper edge and a lower edge of a hole, the tool must be inserted into the hole opening from the upper side of the workpiece to finish the upper edge, and then into the hole opening from the lower side of the workpiece to finish the lower edge.

Alternatively, the workpiece may be turned over. This can be a time-consuming, and therefore an expensive, process.

It is therefore desirable to provide an improved tool and method for finishing holes.

According to a first aspect of the present invention there is provided a tool for finishing a hole in a workpiece, the tool comprising: a neck portion having an axial length; and first and second portions disposed either side of the neck portion and having first and second inclined or angled finishing portions respectively that are inclined or angled inwardly towards the neck portion in opposing directions; wherein the tool is arranged such that it can be disposed within the hole and simultaneously rotated and moved in a circular path so as to finish an edge of the hole with one of the finishing portions. The tool has a diameter that allows it to be inserted into the hole which is to be finished.

The first (or lower) portion which is disposed at the distal end of the neck portion therefore may have a diameter which is less than that of the hole. Finishing an edge of the hole may comprise deburring the edge of the hole, chamfering the edge of the hole, countersinking the hole or applying a lead-in to a tapered hole, for example.

The first and/or second portion comprises at least one inclined finishing surface. The inclined finishing surface may be abrasive. The first and/or second portion may have a plurality of inclined finishing surfaces. The or each inclined finishing surface may be at least part of a frusto-conical surface. For example, the finishing surfaces may be formed from a frusto-conical surface which is interrupted by grooves, or other features,

for example.

The transition between the or each inclined finishing portion or surface and the neck portion may be filleted.

The first and/or second portion may comprise at least one inclined finishing edge, such as a cutting edge or blade. There may be a plurality of inclined finishing (or cutting) edges.

The tool may further comprise a swarf passageway extending at least partially in the longitudinal direction of the tool, the swarf passageway comprising a groove formed in the first portion and/or the neck portion and/or the second portion. The groove may define at least one inclined finishing or cutting edge or blade. There may be a plurality of swarf passageways that extend at least partially in the longitudinal direction. The or each swarf passageway may be curved around the longitudinal axis of the tool. The or each swarf passageway may be helical.

The first and/or the second portion may have a diameter that is greater than the diameter of the neck portion. The first and/or second portions may be coaxial with the neck portion.

The base of the first portion may lie in a plane that is perpendicular to the longitudinal axis of the tool. This may allow the tool to apply a flat surface to a blind hole.

The tool may further comprise a shaft portion which is arranged to be attached to a machine, such as a computed numerically controlled machine.

The tool may be integrally formed. The tool may be machined from a solid carbide blank, for example. The tool may be a deburring tool, a countersinking tool or a chamfering tool, for example.

The present invention also relates to a method of finishing a through-hole in a workpiece, the method comprising: inserting a tool in accordance with any statement herein into the hole so that the tool extends through the entire thickness of the hole and so that the first and/or second inclined finishing portion is adjacent to a first and/or second edge of the hole; and simultaneously rotating the tool about its longitudinal axis and moving the tool in a circular path that is concentric with the hole, thereby finishing the first and/or second edge of the hole. This method allows the underside edge of a hole to be finished by inserting a tool from the upper side.

The method may further comprise moving the tool in the axial direction so that the second inclined finishing portion is adjacent to the second edge of the hole; and simultaneously rotating the tool about its longitudinal axis and moving the tool in a circular path that is concentric with the hole, thereby finishing the second edge of the hole. The tool may be inserted into the hole so that the tool is coaxial with the hole and then moved in the radial direction so that the first and/or second inclined finishing portion is adjacent the first and/or second edge. Finishing the first and or second edge of the hole may deburr or chamfer the edge.

The present invention further relates to a method of finishing a blind hole, comprising: inserting a tool in accordance with any statement herein into the hole; and simultaneously rotating the tool about its longitudinal axis and moving the tool in a circular path that is concentric with the hole, thereby machining a chamferred undercut to the hole.

The second inclined finishing portion of the tool may be moved or inserted so that it is adjacent to the open edge of the hole. The tool may be simultaneously rotated about its longitudinal axis and moved in a circular path that is concentric with the hole so as to finish the open edge of the hole. Finishing the open edge of the hole may deburr or chamfer the edge. The hole may be a tapped hole and any of the aforementioned methods may include machining a hole, by drilling for example, and tapping the hole.

The invention also concerns a numerically controlled machine comprising a tool in accordance with any statement herein arranged to perform a method according to any

statement herein.

In a broad aspect the invention relates to a tool for finishing an edge of a workpiece, the tool comprising: a neck portion having an axial length; and a first portion disposed at the distal end of the neck portion and having a first inclined finishing portion inclined inwardly towards the neck portion in a direction away from the distal end of the tool; wherein in use the tool is disposed relative to the workpiece such that the first inclined finishing portion is adjacent to the edge the workpiece, and wherein the tool is simultaneously rotated and moved in a path so as to finish the edge of the workpiece with the first finishing portion. The edge may be the internal edge of a hole or the external edge of a workpiece.

The tool may further comprise a second portion disposed on the opposite side of the neck portion to the first portion, the second portion comprising a second inclined finishing portion inclined inwardly towards the neck portion in a direction towards the distal end of the tool.

The invention may comprise any combination of the features and/or limitations referred to herein, except combinations of such features as are mutually exclusive.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 schematically shows a tool according to an embodiment of the present invention; Figure 2 schematically shows an enlarged view of the distal end of the tool of Figure 1; Figure 3 schematically shows a perspective view of the tool of Figure 1; Figure 4 schematically shows the tool of Figure 1 inserted into a hole in a workpiece; Figure 5 schematically shows the tool of Figure 1 inserted into a through-hole in a workpiece and positioned so as to finish the lower edge of the hole; Figure 6 schematically shows the machining path of the tool when used to finish a hole; Figure 7 schematically shows the tool of Figure 1 inserted into a hole in a workpiece and positioned so as to finish the upper edge of the hole; Figure 8 schematically shows a workpiece having a hole finished by the tool shown in Figure 1; Figure 9 schematically shows the tool of Figure 1 inserted into a blind-hole in a Figure 10 schematically shows the tool of Figure 1 inserted into a blind-hole in a workpiece and offset from the axis of the hole; and Figure 11 schematically shows a workpiece having a blind hole finished by the tool shown in Figure 1.

As shown in Figures 1 and 2, the hole finishing tool 10 is elongate and comprises a shaft 12 portion, an upper portion 14, a neck portion 16 and a lower portion 18. The shaft, upper portion, neck portion and lower portion are coaxial with one another. The upper and lower portions 141 18 are disposed either side of the neck portion 16 and the shaft 12 is disposed above the upper portion 14. The diameters of the shaft 12 and upper portion 14 are substantially the same, the diameter of the lower portion 18 is slightly smaller than that of the upper portion 14 and the diameter of the neck portion 16 is less than the diameters of the upper and lower portions 14, 16.

The upper portion 14 comprises an upper axial portion 20 and an upper inclined finishing portion 22. The lower portion 18 comprises a lower axial portion 24 and a lower inclined finishing portion 26. In each case, the inclined finishing portion 22, 26 is disposed between the axial portion 20, 24 and the neck portion 16. The axial portions 20, 22 have a constant diameter and the inclined finishing portions 22, 26 taper radially inwardly from the larger diameter axial portion 20, 24 to the smaller diameter neck portion 16. The upper and lower finishing portions 22, 26 are inwardly inclined in opposing directions so that an oblique angle of between 90 and 180 is formed between the inclined finishing portion and the neck portion.

With reference to Figure 3, in this embodiment the upper and lower finishing portions 22, 26 comprise frusto-conical surfaces and inclined cutting edges. The transition between each of the frusto conical surfaces and the neck portion 16 is filleted 23, 27.

The tool 10 is further provided with three swarf passageways 28 that extend from the lower tip (distal end) of the tool to the upper portion of the tool in the general axial direction. The swarf passageways 28 curve around the longitudinal axis of the tool and in this embodiment are helical. Each swarf passageway 28 is a groove that is cut in the lower portion 18, the neck portion 16 and the upper portion 14. The swarf passageways 28 interrupt the frusto-conical surfaces of the inclined finishing portions 22, 26 and divide them into three parts. The grooves also define cutting edges 30, 32 in the upper and lower portions 14, 18 respectively. Each cutting edge 30, 32 comprises an upper and lower inclined cutting edge 30a, 32a, where the groove interrupts the inclined finishing surfaces 22, 26, and a cutting edge 30b, 32b that is not radially inclined with respect to the tool axis and which is defined by the groove extending the axial portion 20, 24. The base, or tip, 34 of the lower portion 18 is substantially flat and lies in a plane that is perpendicular to the longitudinal axis of the tool 10.

The finishing tool 10 can be used with conventional computed numerically controlled (CNC) machines to finish holes that have already been machined (for example by drilling) in metal workpieces, for example. Finishing the hole may comprise chamfering, deburring or countersinking the hole, for example.

The finishing tool 10 may be used to finish a through-hole 2 that has been machined in a metal workpiece 1. As shown in Figure 4, the tool 10 is inserted into the hole 2 such that it extends through the entire thickness of the hole 2 and is coaxial with the hole 2.

In order for this to be possible, the diameter of the lower portion 18 must be smaller than the diameter of the hole 2. As shown in Figure 5, the tool 10 is then moved radially outwards so that the lower inclined finishing portion 26 is in contact with the lower edge 3 of the hole 2. The longitudinal axis of the tool 10 is now offset from the axis of the hole 2. With reference to Figure 6, the tool 10 is then simultaneously rotated about its longitudinal axis T and moved it in a circular path P centred on the axis H of the hole 2. This action causes the inclined cutting edges 32a of the lower inclined finishing portion 26 to chamfer the entire circumference of the lower edge 3 of the hole 2 by cutting. The chamfer angle applied to the lower edge 3 of the hole corresponds to the angle of inclination of the cutting edge 32a. The swarf cut from the lower edge 3 of the hole by the cutting edge 32a falls downwards and away from the workpiece.

The tool 10 is then moved radially inwards so that it is coaxial with the hole 2 and is then moved axially downwards and radially outwards so that the upper inclined finishing portion 22 is in contact with the upper edge 4 of the hole 2 (Figure 7). The longitudinal axis of the tool 10 is now offset from the axis of the hole 2. The tool 10 is then moved in the same manner as shown in Figure 6 which causes the upper inclined cutting edge 30a of the upper inclined finishing portion 22 to apply a chamfer to the upper edge 4 of the hole 2 by cutting. The chamfer angle corresponds to the angle of inclination of the upper inclined cutting edge 30a. The swan cut from the upper edge 4 of the hole falls downwards and away from the workpiece. The tool 10 is then moved radially inwardly so that it is coaxial with the hole 2 and is retracted out of the hole 2. The workpiece having a finished hole 2 having upper and lower chamfered edges 3, 4 is shown in Figure 8. The filleted transitions 23, 27 between the upper and lower finishing portions 22, 26 and the neck portion 16 provides a rounded lead-in 3a, 4a to the hole 2. This may prevent a burr being formed on the edges between the chamfers and the hole 2.

In the above description it has been described that the lower edge 3 is finished first, and then the upper edge 4 is subsequently finished. However, it is possible to finish the upper edge followed by the lower edge. Also, the length of the neck portion 16 may be chosen such that the upper and lower edges 3, 4 can be finished (chamfered or deburred, for example) at the same time.

The finishing tool 10 may also be used to finish a blind hole 2 that has been machined in a metal workpiece 1. As shown in Figure 9, the tool 10 is inserted into the hole 2 such that the tip 34 of the tool 10 is in contact with the bottom of the hole 2 and is tool 10 coaxial with the hole 2. As shown in Figure 10, the tool 10 is then moved radially outwards so that the lower axial portion 24 is in contact with the inner wall of the hole 2 and the upper inclined finishing portion 22 is in contact with the upper edge 4 of the hole 2. The longitudinal axis of the tool 10 is now offset from the axis of the hole 2.

The tool 10 is then simultaneously rotated about its longitudinal axis T and moved it in a circular path P centred on the axis H of the hole 2 (as shown in Figure 6).

This causes the upper inclined cutting edge 30a to apply a chamfer to the entire circumference of the upper edge 4 of the hole by cutting. The lower portion 18 machines a chamfered undercut to the blind hole 2 by cutting with the lower cutting edges 32a, 32b. The swan created by machining an undercut is directed away from the bottom of the hole by the swan passageways 28 which direct the swarf upwards and out of the hole 2. The workpiece having a finished hole 2 having a chamfered undercut 5 and an upper chamfered edge 3 is shown in Figure 11.

The chamfer may be applied to the edges 3, 4 of the hole 2 in order to deburr the edges. If the hole is a threaded hole 2 then the chamfer may provide a lead-in for the thread. If the transition between the inclined surface and the neck portion 16 is filleted, this will provide a chamfer or lead-in having a rounded edge corresponding to the radius of curvature of the fillet. This may prevent a burr being formed on the deburr if the tool is worn or is being used on harder metals.

It is important that the diameter of the lower portion 18 of the tool 10 is less than the diameter of the hole 10 so that the tool can extend into the hole 10. The dimensions of parts of the tool 10 can be chosen depending on the application. For example, the angle between the inclined finishing portions 22, 26 can be chosen to give the desired chamfer angle. Further, the length of the neck portion 16 can be chosen depending on the depth of the hole or the thickness of the workpiece.

Although it has been described that a chamfer angle is applied by cutting, the tool may comprise upper and lower inclined abrasive surfaces so that the chamfer is applied to the edges of the hole by abrading away material.

Although in the foregoing description it has been described that there are upper and lower inclined finishing portions, there may only be a lower finishing portion which is disposed towards the distal end of the tool and which is inclined inwardly towards the neck portion in a direction away from the distal end of the tool.

The finishing tool 10 is suitable for any size of hole and can be dimensioned depending on the geometry of the hole and the workpiece. The tool 10 is simple to use with conventional CNC machines and both edges of a through-hole can be finished without the need to turn over the workpiece. The CNC machine can be programmed to carry out the necessary deburring, countersinking or chamfering action which results in a high level of repeatability. This ensures a high quality finished component.

The tool 10 may be manufactured from a solid carbide blank. The tool may therefore be a single integrated piece. This reduces the cost of the tool and allows the tool to be manufactured to a high tolerance. -11 -

Claims

CLAIMS1 A tool (10) for finishing a hole (2) in a workpiece (1), the tool comprising: a neck portion (16) having an axial length; and first and second portions (14, 18) disposed either side of the neck portion and having first and second inclined finishing portions (22, 26) respectively that are inclined inwardly towards the neck portion in opposing directions; wherein the tool is arranged such that it can be disposed within the hole and simultaneously rotated and moved in a circular path so as to finish an edge of the hole with one of the finishing portions.
2 A tool according to claim 1, wherein the first and/or second portion (14, 18) comprises at least one inclined finishing surface.
3 A tool according to claim 2, wherein there are a plurality of inclined finishing surfaces.
4 A tool according to claim 2 or 3, wherein the or each inclined finishing surface is at least part of a frusto-conical surface.
5 A tool according to any of claims 2-4, wherein the transition between the or each inclined finishing surface and the neck portion is filleted.
6 A tool according to any preceding claim, wherein the first and/or second portion (14, 16) comprises at least one inclined finishing edge (30a, 32a).
7 A tool according to claim 6, wherein there are a plurality of inclined finishing edges (30a, 32a).
8 A tool according to any preceding claim, further comprising a swarf passageway (28) extending at least partially in the longitudinal direction of the tool, the swan passageway comprising a groove formed in the first portion (14) and/or the neck portion (16) and/or the second portion (18).
9 A tool according to claim 8 when appended to claim 6 or 7, wherein the groove defines the at least one inclined finishing edge (30a, 32a).
A tool according to claim 9, wherein there are a plurality of swarf passageways (28) extending at least partially in the longitudinal direction.
11 A tool according to claim 9 or 10, wherein the or each swarf passageway (28) is curved around the longitudinal axis of the tool.
12 A tool according to claim 11, wherein the or each swarf passageway (28) is helical.
13 A tool according to any preceding claim, wherein the first and/or the second portion (14, 18) has a diameter that is greater than the diameter of the neck portion (16).
14 A tool according to any preceding claim, wherein the first and/or second portions (14, 18) are coaxial with the neck portion (16).
A tool according to any preceding claim, wherein the tip (34) of the tool in a plane that is perpendicular to the longitudinal axis of the tool.
16 A tool according to any preceding claim, further comprising a shaft portion (12) which is arranged to be attached to a machine.
17 A tool according to any preceding claim, wherein the tool (10) is integrally formed.
18 A tool according to any preceding claim, wherein the tool (10) is a deburring tool.
19 A method of finishing a through-hole in a workpiece, the method comprising: inserting a tool (10) in accordance with any of claims 1-18 into the hole (2) so that the tool extends through the entire thickness of the hole and the first and/or second inclined finishing portion (22, 26) is adjacent to a first and/or second edge (3, 4) of the hole; and simultaneously rotating the tool about its longitudinal axis and moving the tool in a circular path that is concentric with the hole, thereby finishing the first and/or second edge of the hole.
20 A method according to claim 19, further comprising: moving the tool (10) in the axial direction so that the second inclined finishing portion (22) is adjacent to the second edge (4) of the hole; and simultaneously rotating the tool about its longitudinal axis and moving the tool in a circular path that is concentric with the hole, thereby finishing the second edge of the hole.
21 A method according to claim 19 or 20, wherein the tool (10) is inserted into the hole (20) so that the tool is coaxial with the hole and then moved in the radial direction so that the first and/or second inclined finishing portion (22, 26) is adjacent the first and/or second edge (3, 4).

-14 -
22 A method according to any of claims 19-21, wherein finishing the first and or second edge (3, 4) of the hole deburrs or chamfers the edge.
23 A method of finishing a blind hole, comprising: inserting a tool (10) in accordance with any of claims 1-18 into the hole (2); and simultaneously rotating the tool (10) about its longitudinal axis and moving the tool in a circular path that is concentric with the hole, thereby machining a chamferred undercut (5) to the hole.
24 A method according to claim 23, wherein the second inclined finishing portion (22) of the tool is adjacent to the open edge (3) of the hole (2) and wherein the tool is simultaneously rotated about its longitudinal axis and moved in a circular path that is concentric with the hole to finish the open edge of the hole.
A method according to claim 23 or 24, wherein finishing the open edge (3) of the hole deburrs or chamfers the edge.
26 A method according to any of claims 19-25, wherein the hole is a tapped hole.
27 A numerically controlled machine comprising a tool in accordance with any of claims 1-18 and arranged to perform the method of any of claims 19-26.
28 A tool or method substantially as described herein with reference to the accompanying drawings.