GB2150481A

GB2150481A - Machine tool posts

Info

Publication number: GB2150481A
Application number: GB08422616A
Authority: GB
Inventors: Alan Greig; Roy Alfred Gaved; Roy Howard
Original assignee: Sandvik Ltd
Current assignee: Sandvik Ltd
Priority date: 1983-09-09
Filing date: 1984-09-07
Publication date: 1985-07-03
Also published as: DE3432693A1; GB8324162D0; GB8422616D0; FR2551684A1; IT1225758B; GB2150481B; IT8422481A0; FR2551684B1

Abstract

A tool post assembly has mutually transverse bores (4, 6) in which drawbars (14, 16) are located, each having a cutting tool (62, 66) mounted releasably on its front end. At the front of the bores there are locating and supporting faces (8, 10, 32, 34, 36, 38) for the cutting tools, which can be drawn into firm engagement therewith by moving the associated drawbar rearwards in its bore. The bore (4) is located close to the side face (10) of the assembly to enable facing and parting-off tools to be used with a minimum obstruction, and to this end locating faces (34, 38) at the front of the other bore (6) are recessed into its associated side face (10), that other bore being utilisable for mounting cutting tools as boring bars. <IMAGE>

Description

SPECIFICATION Tooling for machine tools This invention relates to tooling for machine tools such as lathes.

A lathe tool post holds a number of cutting tools that are brought into use in sequence by rotating the post. Typically, the post comprises a platform with a number of top clamps that can be tightened onto cutting tools mounted along the edges of the platform to project from the corners thereof, to fix them to the tool post. Rotation of the post can then induce each cutting tool in turn to an operative position. Such an arrangement is relatively bulky, and suffers the inconvenience that with each replacement of a cutting tool it is necessary to perform a setting operation to ensure the tool is correctly positioned in the tool post.

More recently, cutting tools have been introduced with a form of tool holder that dispenses with the need for resetting when a tool is replaced. Such cutting tools are described in European patent specifications 0 010 074 and 0055998. A single such tool can be clamped by its holder body on a fixed tool post, since cutting elements can be easily substituted while the holder body remains fixed on the tool post, instead of deploying a number of tools on a conventional indexing tool post. However it may be difficult to achieve this simplification in practice if it is required to perform some sequences of operations, e.g. facing and boring.

According to one aspect of the present invention there is provided a tool post body comprising two mutually transverse bores, one of said bores being disposed close to a first side face of the body and substantially parallel thereto to open into a second side face transverse to the first side face close to a junction of said side faces, the bores being arranged to receive respective tool holders for holding cutting tools and the body providing locating means for supporting the tools held by the tool holders in fixed positions projecting from the respective side faces.

According to another aspect of the invention, there is provided a tool post assembly comprising a body as aforesaid, and tool holders disposed in said two mutually transverse bores of the body, said tool holders each comprising means for holding a cutting tool against a fixed location on the tool post, the tool holder in said bore close to the first side face of the body and the associated tool location being arranged to support the cutting tool so that it projects beyond the plane of said first side face.

Each of the bores preferably terminates at a front end face with side portions projecting forwards from opposite sides of said end face to provide engagements for clamping the cutting tool firmly in position laterally of the bore.

In a prefered arrangement of the assembly, said transverse bores intersect each other and at least one of the tool holders comprises a cut-away portion to permit the mutually transversely located tool holders to be independently displaceable in their bores for clamping and unclamping their respective cutting tools.

An embodiment of the invention is illustrated by way of example in the accompanying drawings, in which: Figure 1 is an isometric view of a tool post assembly according to the invention that also shows respective tools for the two tool holders, Figures 2 and 3 are plan and side views of the tool post assembly of Figure 1, and Figures 4 and 5 are diagrammatic illustrations of details of the two tool holders in the assembly of Figures 1 and 2 in the region of their crossing.

The illustrated assembly comprises a tool post body 2 of square plan form arranged to be carried in a fixed position on a slide of a lathe. Two main bores 4, 6 run through the body parallel to a pair of mutually transverse faces 8, 10 of the body that form the radial and axial leading faces respectively during cutting operations on a workpiece. The bore opening into the radial leading face 8 is disposed very close to the corner junction of the two faces. The bore 6 opening into the axial leading face is offset towards the corner junction but is further from it than the bore 4.

Tool holders 14, 16 are provided in the bores 4, 6 respectively, each comprising a drawbar 18 terminating at its front end in an enlarged portion 20 intended to be received in a complementary recess in a cutting tool. Each drawbar can be displaced axially in its bore, against the force of a compression spring 22, by turning a hand lever 24 engaging a threaded rear end of the drawbar 18 to draw the rear face of the cutting tool into firm engagement with a respective datum face, transverse to the tool holder bore, providing a location for the cutting tool, which has a known dimension from its cutting edge to its rear face abutted against the datum face. In the example illustrated, the side faces 8, 10 provide these datum faces.

In each case, the front of the bore 4, 6 opens into a recess 30 which comprises pairs of parallel side walls 32, 34. Respective support platforms 36, 38 for the cutting tools are provided at the bottom of the recesses either as fixed integral parts of the tool box body or as separate parts that are adjustable in height, and at the top of each recess the side walls are succeeded by divergent faces 34a to facilitate the insertion of the cutting tool into the recess. In the case of the radial leading face 8, shoulders 40 project from the face to provide the sides of the recess whereas the axial leading face 10 has its recess set into it. Together with the use of the shorter support platform 38 the result is that the cutting tool mounting and clamping means on the axial leading face project only a very small amount from that face.

The axes of the two tool holders 14, 16 are at different heights but their bores 4, 6 intersect. There are reliefs 44, 46 in the upper face of the lower holder 14 and in the lowerface of the upper holder 16 where the holders cross. In each case the axial length of the relief is somewhat greater than the width of the opposed face of the other tool holder in order to allow freedom for axial movement when a cutting tool is to be clamped or released. The relief 44 in the lower tool holder is accommodated entirely within the main cylindrical length of the holder fitting its bore 4. However, that bore also intersects the recess in the axial leading face 10 and a further relief 54 is provided in the lower tool holder on the side nearer the face 10 so as not to obstruct the rearwards movement of the cutting tool when it is being drawn into contact with its datum face.

In use, with the tool post body fixed on a lathe slide, a cutting tool having a rear portion complementary to the enlarged portion 20 of a drawbar 18 is slipped onto the portion 20 in the appropriate one of the two tool holders 14, 16 and the clamping lever 24 is rotated to retract the drawbar 18 against the biasing spring 22. The bifurcated rear of the cutting tool is thereby forced into firm engagement with its datum face and the side faces of the recess so that it is rigidly held with its cutting edge at a known distance from the tool post datum. For a further description of the form of releasable engagement between the cutting tool and its holder, and of some possible modifications thereof, reference can be made to the aforementioned European patents 0 010 074 and 0055998.

Figure 1 illustrates a cutting tool 62, comprising a hard metal cutting insert 64, to be mounted in the tool holder of the radial leading face to overhang the axial leading face. This tool position may be chosen, typically, for end facing operations or for external turning. It will be noted that because of the very small projection ofthetool holder 16 and support platform 38 on the axial leading face 10, the tool post can be brought very close to the workpiece (or the lathe chuck) so as to achieve a very rigid set-up, aided by the closeness of bore 4 to the axial leading face. For internal turning operations, the tool holder of the axial leading face 10 is used to mount a boring bar 66 shown here with a replaceable cutting tip 68.

In each instance it is possible to change the cutting tool easily and quickly by releasing the tool from its drawbar. The replacement, mounted on the same tool holder or the alternative tool holder, as appropriate, is brought to a known position by clamping it against its associated datum face so that a series of different cutting operations can be performed with little loss of time for tool replacement and setting.

It will be understood that the ability to change over between the two tool holders when machining the same workpiece requires that the cutting tools have a common centre height (cutting edge height), as indicated in Figure 3 at C, and that the form of each cutting tool will be chosen to give this result by compensating for the different heights of the two tool holders.

Claims

1. Atool post body comprising two mutually transverse bores, one of said bores being disposed close to a first side face of the body and substantially parallel thereto to open into a second side face transverse to the first side face close to a junction of said side faces, the bores being arranged to receive respective tool holders for holding cutting tools and the body providing locating means for supporting the tools held by the tool holders in fixed positions projecting from the respective side faces.

2. A tool post body according to claim 1, wherein each bore terminates at a front end face and side portions project forwards from opposite sides of said end face to provide engagements for supporting the cutting tool in position laterally and nonrotatably of the bore.

3. A tool post body according to claim 2, wherein said side portions at said second side face of the body project forwards of said second side face.

4. Atool post body according to claim 2 or claim 3, wherein said side portions at said first side face of the body are recessed into said first side face.

5. A tool post assembly comprising a tool post body according to any one of the preceding claims and tool holders disposed in said two mutually transverse bores of the body, said tool holders each comprising means for holding a cutting tool against a fixed location on the tool post, the tool holder in said bore close to the first side face of the body and the associated tool location being arranged to support the cutting tool so that it projects beyond the plane of said first side face.

6. Atool post assembly according to claim 5, wherein said transverse bores intersect each other and at least one of the tool holders comprises a cut-away portion to permit the mutually transversely located tool holders to be independently displaceable in their bores for clamping and unclamping their respective cutting tools.

7. Atool post assembly according to claim 6, wherein said first side face of the body is provided with a recess in which the bore leading to said first side face terminates, said recess interesecting the bore opening into the second side face and the tool holder in said second bore comprising a cut-away portion providing clearance for the tool holder.

8. A tool post body constructed and arranged for use and operation substantially as described herein with reference to the accompanying drawings.

9. Atool post assembly constructed and arranged for use and operation substantially as described herein with reference to the accompanying drawings.