GB2441438A

GB2441438A - Tool holder for a turret lathe

Info

Publication number: GB2441438A
Application number: GB0716802A
Authority: GB
Inventors: Colin Cooper
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-08-31
Filing date: 2007-08-31
Publication date: 2008-03-05
Anticipated expiration: 2027-08-31
Also published as: GB2441438B; GB2441310A; GB0617124D0; GB0716802D0

Abstract

The tool holder is adapted to be received in the bore of a tool support of a turret lathe. The holder includes a tubular body 4 having outer and inner surfaces, the outer surface being provided at one end with a threaded portion. The inner surface defines a cavity to receive a collet 3 which serves to hold the tool. A portion of the inner surface locates and cooperates with the received collet. A tubular collet clamping means 1 includes outer and inner surfaces. The inner surface of the clamping means engages the threaded portion of the body and cooperates with the collet when it is received in the cavity. The engagement of the clamping means with the threaded portion of the body causes pressure to be applied to the received collet, thereby causing the tool to be held to be gripped by the collet. The outer surface of the clamping means has a maximum edge-to-edge distance the same or less than the maximum edge-to-edge distance in a cross-section of the body. A tool stop element 5 is located within the cavity to engage with the body to provide a support for the tool. The body may also include a channel and a groove for coolant to flow.

Description

* 2441438 Tool holder

Field of the Invention

The present invention relates to a tool holder for a machine tool, especially for use in a turret lathe.

Background of the Invention

Turret lathes are commonly used machine tools, particularly for producing turned components such as screws, shafts or bolts. The turret of such a lathe provides a number of tool supports mounted on different faces of the turret, therefore allowing several different tools, such as drills of different diameters, to be positioned on the turret. Rotation of the turret allows the tool to be used to be changed, without the need for removing either the workpiece or the tools from the lathe. This facilitates complicated machining processes and affords the possibility of high speed operation.

Generally, the tool supports mounted on the turret are adapted to incorporate a bore into which the tool is inserted. In order to fasten the tool securely in place, a tool holder is generally required. Commonly, the tool holder is a simple bushing which is machined to match the shank of the tool it is to hold as well as * *e* the tool support bore. Because the range of sizes of commercially available bushings is limited, it is often necessary to turn down the shank of a tool before it can be inserted, to make it compatible with the bushing. The inconvenience of making these adjustments when a new tool is S. *S * * inserted makes the typical tool changeover time relatively long * which can be very costly in terms of manufacturing efficiency.

One approach to improving the changeover time is to use a tool holder that employs a collet to grip the inserted tool, rather than a conventional bushing. This provides much greater adjustability because a given collet can accept tools with a significant range of diameters. This approach is adopted, for example, in US 6,145,420, in which a novel turret design is described, which allows a number of tools to be secured in positions by means of collets. However in order to apply this approach to a conventional turret lathe, it would be necessary to replace the entire turret assembly, which would be a costly and complex process.

A further problem in the use of turret lathes is the very limited clearance which typically exists in use between the work piece and the surface of the tool support. This is particularly restricted if the tool holder protrudes beyond the tool support surface. The crowding resulting from the proximity of tools, tool holders and work piece means that collisions can occur between them, potentially resulting in serious damage which may be costly and time-consuming to remedy. This is a particular problem when using a collet-based tool holder, because the collet clamping means typically extends beyond the face of the tool support, in order to allow it to be tightened to the required extent to narrow the collet bore and secure the tool.

This is the case, for example, with an existing collet-based tool holder marketed by Weston Tooling.

Another difficulty encountered in operating any high speed cutting tool is the great heat generated by friction as the tool operates on the work piece. This can result in damage to both : the tool and the work piece unless the tool is actively cooled during operation. This can be achieved by spraying a coolant on to the tool. For the best effect the coolant should be directed along the length of the tool but it is difficult to achieve this satisfactorily in a turret lathe using a conventional tool holder assembly.

There therefore remains a continuing need for the development of an improved tool holder for use in a turret lathe in order to overcome the problems associated with current tool holders.

Summary of the Invention

The present invention is based on the finding that it is possible to construct a tool holder which can be accommodated in the tool support of a conventional turret lathe and which uses a collet to secure the tool in position but which does not protrude beyond the surface of the tool support, thus providing for rapid tool changeover without increasing crowding in the vicinity of the tools and work piece. It has further been found that such a tool holder can conveniently be adapted to provide a coolant flow pathway which allows a very effective cooling spray to be directed along the length of a tool in operation.

The invention therefore provides in a first aspect a tool holder adapted to be received in the bore of a tool support of a turret lathe, said tool holder comprising: a tubular body having outer and inner surfaces, the outer surface being provided at one end with a threaded portion, the inner surface of the body defining a cavity adapted to receive a collet which serves to hold a tool, a portion of said inner surface being adapted to locate and cooperate with said received collet; S..

tubular collet clamping means having outer and inner surfaces, S...

.. the inner surface of the clamping means being adapted to engage the threaded portion of the body and to cooperate with the collet when it is received in the cavity, such that engagement of the clamping means with the threaded portion of the body causes pressure to be applied to the received collet, thereby causing the tool to be held to be gripped by the collet, the outer surface of the clamping means having a maximum edge to edge distance in a cross-section which is the same or less than the maximum edge to edge distance in a cross-section of the body, the collet clamping means being provided at one end with an aperture through which the tool to be held protrudes; and a tool stop element located within the cavity of the body and adapted to engage with the body so as to provide a support for the tool to be held.

Tool holder assemblies comprising a tool holder according to the first aspect of the invention having a collet serving to hold a tool received in the cavity of the body of the tool holder, a tool support for a turret lathe incorporating such a tool assembly and a tool held in such a tool assembly form further aspects of the invention, as do methods of using the tool holder.

Other features of the present invention will become apparent from the following examples. Generally speaking, the invention extends to any novel feature, or combination of features disclosed in this specification and features described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. * * * *.*

Detailed description of the Invention S.. *SSS

The tool holders according to the invention may suitably be used in conjunction with any turret conventionally used in the art including normal and Vdu turrets. *5 *S * S S

S S

The body of the tool holder according to the invention and may be made of any suitably strong and durable material, such as hardened tool steel, preferably H13 plasma nitrided steel. The tubular body is preferably cylindrical and will be of such internal and external dimensions that the tool holder may be accommodated snugly within the bore of the tool support and can receive the desired collet within the cavity defined by its inner surface. The outer surface of the body will be adapted such that when the tool holder is received in the bore of a tool support of a turret lathe, at least part of the outer surface of the body is in contact with the inner surface of the tool support.

It will be appreciated that the chosen outer dimensions of the body will depend on the dimensions of the tool support in which the holder is to be accommodated. Similarly, the body may be formed with different inner surface dimensions depending on the dimensions of the collet to be inserted. Typically, the body will have an outer diameter of 25, 32, 40 or 50 mm depending on the diameter of the chosen tool support.

The collet receiving inner surface of the body for use in a tool holder according to the invention is adapted to locate and cooperate with the received collet. Suitably, the inner surface is shaped so as to be complementary to the size and shape of the collet to be used.

The body may suitably be provided with means for orienting a tool held in the tool holder. Suitably, these means comprise one or more threaded holes through which screws for engaging with the shank of the tool may be received. This hole or holes allow S...

the orientation of a single point cutting tool to centre cutting *5** height. A bolt from the turret can further orientate the holder on the flat or can pass through the orientation hole to contact the tool itself. * . .

S S

The collet clamping means in the tool holder according to the invention may suitably comprise any means which can engage the threaded portion of the body and which can cooperate with the received collet to cause a tool held by the collet to be gripped firmly.

Suitably, the collet clamping means comprise a nut.

It will be appreciated that the dimensions of the clamping means will be chosen such that the maximum edge to edge cross-sectional distance is the same or less than the maximum edge to edge distance of a cross-section of the body so as to ensure that both the body and clamping means can be accommodated within the bore of the tool support in which the assembled tool holder is to be received. Suitably, the clamping means and the body will have a matching outer cross-section, at least at their point of contact, to ensure a close fit between the assembled tool holder and the bore wall of the tool support in which it is to be inserted, although the use of clamping means having a smaller maximum edge to edge distance in cross-section than the body may be envisaged.

The collet clamping means is conveniently adapted at or towards one end on the outer surface to allow engagement with means for tightening the clamping means so as to apply pressure to the collet.

Suitably the inner surface of the clamping means is provided with means suitable for engaging with the threaded portion provided on the outer surface of the body and is adapted to cooperate with a collet received in the tool holder.

.. : Conveniently the inner surface of the clamping means has a threaded portion for engaging with the threaded portion of the body. Suitably the inner surface of the clamping means has a * * I * * * tapered portion which cooperates with the surface of a collet received in the tool holder. This taper suitably has a radial groove to allow high coolant flow (discussed below) to the outside diameter of the collet.

The overall length of the body and clamping means when assembled together will be such that the tool holder according to the invention does not protrude beyond the front plane of the tool support into which the tool holder is inserted such that the tool holder is accommodated entirely within the bore of the tool support.

The tool stop element may comprise any element which can be located within the body and which can engage with the body so as to prevent a tool inserted into the tool holder from sliding backwards within the body cavity in use. Suitably, the tool stop element is a grub screw which engages with a threaded portion provided on the inner surface of the body.

The diameter of the body cavity may suitably be selected to allow a single point tool such as a boring bar to be supported within the cavity.

The tool holder according to the invention may suitably be provided with means for directing a coolant fluid therethrough to allow a jet or flood of coolant fluid to be directed along the length of the tool to be held, passing through the collet and emerging at the front of the tool holder adjacent to the tool.

Cooling the tool in this way is particularly effective because the entire surface area of the tool is coated with coolant, such

I

that more coolant reaches the cutting edge of the tool, even in *.

.. : the case of long tools such as long drills. In tool holders available to date, the coolant fluid is generally provided at an angle on the side of the tool and does not cover the entire tool s S. * S * * * length. In order to force coolant to the cutting edge, it is necessary to modify the tool, for example by providing holes along the length of the tool. Using the tool holder according to the present invention avoids the need for such expensive and complicated additional operations.

Suitably, the means for directing coolant fluid according to the present invention comprise an attachment to a coolant fluid delivery channel and ducting through the holder.

Suitably, the coolant fluid is directed through the slots of the collet. In a particular embodiment, the wall of the body has an channel extending therethrough which connects with a groove formed around the circumference of the inner wall of the body at a point where it is adjacent to the collet when the collet is in position in the body. This will allow coolant flow from outside of the tool holder directly to the collet slots.

Suitably, the tool holder may additionally be provided with a coolant jet-forming element which serves to increase the pressure of the coolant fluid and direct it along the axis of an inserted tool. The jet-forming element is suitably located between the collet clamping means and the received collet.

It will be appreciated that this approach to cooling the tool may be implemented with other collet based tool holder systems by modifying them to convey coolant fluid through the tool support to the collet and along the length of the tool held therein. This forms a further aspect of the present invention.

Preferred embodiments of the tool holder assemblies of the invention are similar to those described above in relation to the tool holder. *** * . . S. I

An embodiment of the invention will now be particularly described by way of non-limiting example with reference to the accompanying drawings in which: *SS

I

Figure 1 shows the tool support of a turret lathe with a tool holder according to the invention inserted in the bore of the tool support; Figure 2 is an exploded view of the components of a tool holder according to the invention; Figure 3 shows a view in partial cross- section of a coolant high volume jet-forming element for use in an embodiment according to the invention; Figure 4 shows a view in partial cross- section of a collet clamping means; Figure 5 shows a section through the head of a tightening tool suitable for insertion into the bore of a tool support in order to engage with the collet clamping means of a tool holder according to the invention; Figures 6 and 7 shows side views in partial cross-section of the body of tool holders according to the invention, Figures 6a and 7a shows views of the end which engages with the collet clamping means and Figures 6b and 7b show views of the other end of the body of a tool holder As shown in Figure 1, a tool holder according to the invention can be inserted into the bore (23) of a conventional tool support (11) on the turret (12) of a turret lathe. Many turret variants are known in the art but in general they all have such tool supports with a bore for accommodating a tool holder and a tool holder according to the present invention is therefore suitable for use with any conventional turret. The tool support has threaded holes (13) into which bolts may be screwed, which will engage with the inserted tool holder, thereby orienting and .... gripping the tool holder firmly in place. If these bolts clamp S...

on a flat plane of a toolholder or tool they will orientate the S...

.. : flat to 900 off the centre line of the bolt. The bolt can pass through hole (7) seen in figure 2 to clamp the tool directly. * S *

* * When inserted in this way into the tool support of a lathe turret, the tool holder is accommodated entirely within the bore of the tool support, so that no part of the tool holder protrudes beyond the face (22) of the tool support. This minimises crowding in the space between the turret and a work piece mounted on the lathe and hence reduces the risk of damaging collisions when the turret rotates to effect a tool changeover or when the machine is working at its centreline.

A typical tool (9) is shown in place in the tool holder, with a surrounding jet of coolant (10) emerging from the tool holder.

The components of a tool holder according to the invention are illustrated in figure 2. The body (4) is adapted at one end to receive a collet (3) and to engage with a nut (1) which acts as a collet clamping means. A coolant jet-forming element (2) may be inserted between the collet (14) and the nut (1) . The other end of the body (4) is adapted to allow insertion of a tool stop element (5). A plate (6) is also provided which, when positioned in the tool support bore at the end distal from that from which the tool projects, acts as an enclosing means for the tool support bore.

Details of the components of the tool holder are shown in figures 3-6. The body portion (4) has a cavity (26) which is defined by the inner surface of the body. A tapered portion (17) of the inner surface is formed towards one end of the body, so that the cavity cross section increases in size towards the end of the body. This allows the body to accommodate a collet (3) The conical surface of the collet cooperates with the tapered portion of the inner surface (17) of the body. When an axial force is applied to the collet by means of engagement with the nut (1), the collet is crushed against the tapered portion of * SI the inner surface (17) so that the collet will grip firmly a tool inserted into it. S. S. * * *

* * The detailed form of the inner surface of the body, and in particular of the tapered portion (17) is accurately machined to match the particular collet to be accommodated. A variety of collets are available commercially, for example ER collets and double angle colj.ets, and the form of the inner surface of the body can readily be formed to accommodate any of these.

Towards the other end of the body, the cavity (26) is narrower and of a substantially constant cross section sufficient to accommodate the base of the tool to be held. This part of the cavity is defined by a threaded inner surface portion (16) Continuous with this portion, and running parallel with it, there is a narrower channel (15) for the passage of coolant fluid.

At the end of the body in which the collet is received, there is provided a threaded portion (20) of the outer surface of the body, which is adapted to engage with the nut (1). Proximal to this portion, there is an intermediate portion of the outer surface (27) which, when the tool holder is inserted into a tool support, will form a close fit around the entire circumference of the body between the body and the bore wall of the tool support. This provides for accurate location of a tool when it is inserted into the tool holder, and also ensures that coolant fluid cannot leak out around the outside of the body. Towards the other end of the body, the outer surface is machined so that the greater part of it will similarly maintain close contact with a tool support into which the body is inserted, but portions of the outer surface are here formed as flat surfaces (8), so that when inserted into a tool support a gap will be formed between the tool support and the holder, allowing passage of coolant fluid. S. *. * . S *. S

There are also provided in the body portion one or more threaded holes (7) which pass through the body wall. These are adapted to *. S. * S * * * receive grub screws which will engage with the shank of a tool located in the holder. This is important for orienting tools such as boring bars, where precise orientation is important for accurate cutting.

A tool stop element (5) is located within the cavity of the body. This is conveniently in the form of a conventional grub screw with a diameter selected to allow it to engage with the threaded portion (16) of the inner surface and the diameter of the thread supports tools by a precision fit on the tool diameter. Typically, a different tool holder may be necessary for each tool size. In use, the tool stop abuts the base of the tool which inserted into the holder, hence preventing the tool from sliding backwards within the body cavity when it is pressed against a work piece. The precise location of the tool stop within the cavity may be adjusted by means of the screw threads, to accommodate tools of different lengths. If a tool is to be replaced by another of the same length, the use of a tool stop also helps to minimise changeover time, since the new tool can be immediately inserted at the correct depth.

The nut (1) has an outer surface which matches the outer surface of the body (4), so that it forms a close fit with the bore wall when inserted into a tool holder. The end wall of the nut (20) has a hexagonal raised portion (21) . When the tool holder is located in the bore of a tool support, there will be a gap between the hexagonal raised portion (21) and the bore wall of the support, into which a spanner (24), compatible with the hexagonal portion, may be inserted. This feature allows the tightening of the nut whilst in place in the tool support such that the whole assembly need not protrude from the tool support front. This facilitates tightening of the tool holder assembly, so that an inserted collet is compressed, causing it to grip firmly an inserted tool. An aperture (28) is formed in the end wall of the nut through which a tool, gripped by the holder, may project and through which a jet of coolant fluid may be S. S. * S * * * expelled. ***

S

The inner surface of the nut has a threaded portion (18) at one end which is adapted to engage with the threaded portion of the body (20) . Proximal to this there is a tapered portion (17) of the inner surface. This is shaped so that it will cooperate with the top surface of a collet inserted into the tool holder, causing an axial force to compress the collet when the engagement of the body and the nut is tightened.

A coolant jet-forming disc (2) is located within the cavity defined by the inner surface of the nut. When the tool holder is assembled with a collet in place, this disc is held between the top surface of the collet and a flange formed by the end wall of the nut (20) . This disc has a bore (25) with a shape tailored to direct a coolant jet effectively over an inserted tool. The bore may be in the form of a single drilled hole, with a constant or a tapering cross section, or it may be in the form of a series of slots or holes.

The coolant fluid to be used in conjunction with the tool holder may be any suitable fluid. A mixture of oil and water being preferred, since the oil performs an additional lubricating role. Coolant fluid is pumped through a channel (19) in the tool support and passes into the gap between the flat portion of the body (8) and the bore wall of the tool support. The channel (19) can be drilled into a conventional tool support to connect into the ducting that feeds the conventional coolant jet(29)provided in a typical tool support. The fluid then passes into a gap between the body (4) and the plate 6),the plate acting as an : ... enclosing means, preventing fluid loss at this end of the tool support bore. Next, the fluid passes into the channel (15) which runs alongside the body cavity in which a tool is inserted, * .* .. : through the slots (14) in the collet (3) located in the tool holder, through the bore of the coolant jet-forming disc (2) and out through the aperture (28) in the end wall of the nut (1) * * I S * Alternatively or additionally, as seen in Figure 7, a groove (29) may be formed around the circumference of the inner wall of the body at a position where it will be adjacent to the collet and a connecting channel (30) is provided through the wall of the body allowing coolant to flow from the outside of the tool holder more freely through the slots in the collet. The length of the disc bore is at least the bore diameter in order to concentrate the flow around the tool. The coolant emerges in the form of a jet directed along the axis of the inserted tool. In cases where a small collet is used which is collapsed to the limit of its range the slots (14) in the collet are sufficiently narrow to form an effective jet without the need for a disc (2) It will be appreciated by those skilled in the art that modifications and variations to the embodiments described above may be made in the invention without departing from the scope as described herein. * S * *5* S... * . S... *SSS * S * * S S. .S * . . * *

S *

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Claims

Claims 1. A tool holder adapted to be received in the bore of a tool

support of a turret lathe, said tool holder comprising: a tubular body having outer and inner surfaces, the outer surface being provided at one end with a threaded portion, the inner surface of the body defining a cavity adapted to receive a collet which serves to hold a tool, a portion of said inner surface being adapted to locate and cooperate with said received collet; tubular collet clamping means having outer and inner surfaces, the inner surface of the clamping means being adapted to engage the threaded portion of the body and to cooperate with the collet when it is received in the cavity, such that engagement of the clamping means with the threaded portion of the body causes pressure to be applied to the received collet, thereby causing the tool to be held to be gripped by the collet, the outer surface of the clamping means having a maximum edge to edge distance in a cross-section which is the same or less than the maximum edge to edge distance in a cross-section of the body, the collet clamping means being provided at one end with an aperture through which the tool to be held protrudes; and a tool stop element located within the cavity of the body and adapted to engage with the body so as to provide a support for the tool to be held.

2. A tool holder according to claim 1 which when received in the bore of a tool support of a turret lather does not protrude beyond the front plane of the tool support. *. .. * . . *

3. A tool holder according to claim 1 or claim 2 wherein the portion of the inner surface of the body adapted to locate and cooperate with the received collet tapers inwardly.

4. A tool holder according to any preceding claim wherein the outer surface of the end of the body at which the collet is received is provided with a threaded portion.

5. A tool holder according to any preceding claim wherein the inner surface of the body is provided with a threaded portion for engaging with the tool stop element.

6. A tool holder according to any preceding claim wherein the collet clamping means comprise a nut.

7. A tool holder according to any preceding claim wherein the outer cross-section of the clamping means matches the outer cross-section of the body at the point of contact between the body and clamping means.

8. A tool holder according to any preceding claim wherein the outer surface of the clamping means is adapted to allow engagement with means for tightening the clamping means.

9. A tool holder according to any preceding claim wherein the inner surface of the clamping means is provided with means for engaging with the threaded portion provided on the outer surface of the body and is adapted to cooperate with a collet received in the tool holder. * S * *S

10. A tool holder according to any preceding claim wherein the tool stop element comprises a screw. ** *e * S S *5 S

11. A tool holder according to any preceding claim wherein the :.. body is provided with means for orienting a tool held in the * tool holder.

S *,. *

12. A tool holder according to claim 11 wherein the means for orienting the tool comprise one or more threaded holes adapted to receive one or more screws which engage with the tool held in the holder.

13. A tool holder according to any preceding claim wherein the holder further comprises means for directing a coolant fluid the rethrough.

14. A tool holder according to claim 13 wherein the coolant fluid directing means direct the coolant fluid through a collet received in the holder.

15. A tool holder according to claim 13 or claim 14 wherein at least a portion of the outer surface of the body is formed as a flattened surface such that when the holder is inserted in a tool support, a passage to allow coolant fluid to flow along the outer surface of the body is provided.

16. A tool holder according to any preceding claim wherein the e body has a channel therethrough connecting with a groove formed around the circumference of the inner surface of the body, the groove being located in the portion of the inner surface of the body which is adapted to locate and cooperate with the received collet.

i_I. A tool holder assembly comprising a tool holder according to any preceding claim having a collet received in the cavity of the body of the tool holder. * as. **S

.. : 18. A tool holder assembly according to claim 17 further comprising a tool received in the collet. a. *

 a 19. A tool held in a tool holder assembly according to claim 18.

20. A tool holder substantially as described herein with reference to the accompanying drawings.

21. A tool holder assembly substantially as described herein with reference to the accompanying drawings.

22. A method for holding a tool in a turret lathe substantially as described herein.

23. A method for cooling a tool held in a turret lathe substantially as described herein. * * *** **** S * *5*S *S**

S S *SS * ** * S * * S

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