GB2172534A - Tool holder - Google Patents

Abstract

The holder 4 carries a cutting tool 6 and has a projecting cut limiting device 7 which engages the workpiece W above the tool 6 and thus limits the depth of cut. The tool holder 4 is supported on a tool rest 1 comprising a cylindrical bar disposed parallel to the turning axis TA and along which is slidable a saddle 2 with a guideway 5. The tool holder 4 is directly supported as a sliding fit in the guideway 5 which is disposed laterally of the turning axis TA. An adjustably clamped follower 11 can engage a rear profile edge 14 of a template 15. <IMAGE>

Description

SPECIFICATION Tool holders and arrangements thereof The invention relates to tool holders and tool holder arrangements suitable for use with woodworking lathes, for example. It is particularly, but by no means exclusively, applicable to tool holder arrangements adapted for profile turning of a workpiece.

The turning of wood and like materials normally requires considerable skill in controlling the cutting tool so that it cuts correctly and does not dig into the workpiece. To enable the requisite control to be exercised the tool rest has to be set close to the workpiece, and thus the reduction of a large workpiece of square-section stock to å small diameter necessitates re-setting of the tool rest as the diameter is reduced.

It is an object of the invention to provide an improved tool holder with which the setting of the tool rest is not so critical, so that a considerable reduction in diameter can be achieved without resetting the tool rest, and which prevents the tool digging in and thus gouging pieces out of the workpiece. A further object is to provide such a tool holder which can readily be arranged for profile turning, with the tool following the contour shape of a pattern or template, thus making possible rapid reproduction of the pattern with a minimum of skill being required.

According to the invention a tool holder adapted to be supported on a tool rest carries a cutting tool and has a projecting cut limiting device which engages the workpiece above the tool and thus limits the depth of cut of the latter.

Preferably the tool holder comprises an elongate bar of rectangular section with an inclined bore adjacent the forward end in which the tool is adjustably secured and above which the cut limiting device projects forwardly over the tool. The device may be of inverted hook-like form, being secured to the tool holder at one end and at the other free end engaging the workpiece a short distance above and slightly rearwardly of the cutting edge of the tool.

The tool rest may be a bar which extends parallel to the turning axis and along which is slidable a saddle providing a sliding guide for the tool holder, with a guideway along which the tool holder is advanced into cutting engagement with the workpiece. The tool rest may be a cylindrical bar on which the sliding guide can pivot to vary the inclination of the tool holder and thus, for a given relative setting of the tool and cut limiting device, vary the depth of cut.

For profile turning the tool holder may have a projecting follower which engages the rear profiled edge of a master such as a pattern or template, the contour shape of which is reproduced on the workpiece. This pattern or template is preferably disposed below the tool rest and on the rear side thereof, that is between the tool rest and the operator. The master may be a replica of the workpiece and mounted between centres.

Alternatively, guidance of the tool holder may employ a long bar fixed at right angles to the tool holder with a free end projection which slides in a groove in the tool rest some distance from the tool holder.

The invention will now be described with reference to the accompanying drawings which illustrate, by way of example, a profile turning tool holder arrangement in accordance with the invention. In the drawings: Fig. 1 is a schematic perspective view of the arrangement; Fig. 2 is a view in the direction of the turning axis, showing a position of the tool holder providing a large depth of cut; and Fig. 3 is a similar view showing another tool holder position providing a smaller depth of cut.

In the drawings onlythe arrangement described and a portion of the workpiece Ware illustrated, the arrangement being embodied in a woodworking lathe which is otherwise of conventional form. A tool rest 1 comprises a cylindrical bar disposed parallel to the turning axis TA and with a spacing therefrom which is adjustable. A saddle 2 with a complementary underneath groove 3 is mounted on and slidable along the tool rest 1.

The saddle 2 provides a sliding guide for a tool holder 4 which is directly supported on the saddle 2 which has a rectangular section guideway 5. The elongate tool holder 4 is a bar of rectangular section which is a sliding fit in the guideway 5, and at the front end the tool hdlder 4 has a downwardly projecting nose section 4a with an inclined bore in which a cutter tool 6 is adjustably secured, by means of a clamp screw for example, at the correct cutting angle relative to the workpiece.

A cut limiting device 7 comprises a length of rod bent into an inverted hook shape and welded at one end to the top of the tool holder 4 at 8, close to the end nose section 4a. The leading edge of the device 7 at 9 engages the workpiece W during cutting to limit the depth of cut of the adjacent cutting edge 10 of the tool 6. The tool 6 is positioned and clamped in the tool holder 4 so that the cutting edge 10 is disposed adjacent and slightly forwardly of the edge 9 of the cut limiting device 7. The provision of the cut limiting device 7 in conjunction with a long tool holder 4 enables a large square section workpiece to be reduced to a small diameter with a single setting of the tool rest 1.

A tracing finger or follower 11 projects downwardly from the tool holder 4 and is adjustable along a longitudinal slot 12. It is clamped in the adjusted position by a lever nut 13, and it is engageable with the rear edge profile 14 of a pattern or template 15 secured below and rearwardly of the tool rest 1. In order to reproduce the pattern profile accurately the tool cutting tip 10, the edge 9 of the cut limiting device 7 and the follower 11 are of the same section and size.

The arrangement illustrated allows the tool holder 4 to be slid in two directions during the profile turning; a forward feed at right angles to the turning axis TA sliding on the saddle 2 into cutting engagement with the workpiece W, and longitudinal traverse by sliding of the saddle 2 along the tool rest 1. During such traverse the cut limiting device 7 at all times limits the depth of cut, so that the tool 6 does not dig in and gouge pieces out of the work.

Figs. 2 and 3 illustrate how the angular position of the tool holder 4 determines the effective depth of cut, which can be varied by pivoting the saddle 2 around the cylindrical tool rest 1. Upward pivoting increases the depth of cut by withdrawing the cut limiting device 7 relative to the tool 6 with Fig. 2 showing a large depth of cut, and downward pivoting advances the cut limiting device 7 relative to the tool 6 as shown by Fig. 3 to provide a smaller depth of cut.

The follower 11 engages the edge profile 14 to determine the maximum inward movement of the tool holder 4, so that the edge profile of the pattern or template 15 is accurately reproduced on the turned surface of the workpiece W.

Although the cut limiting device is shown in the illustrated embodiment as non-adjustablyfixed to the tool holder 4, it may be adjustably mounted thereon. Such an adjustable mounting provides greater versatility for the relative adjustment of the tool 6 and the device 7 when setting up the tool holder arrangement. It will also be appreciated that the tool holder 4 can be used directly supported on the tool rest 1, without using the sliding guide or saddle 2, when the pattern or template 15 is not employed.

Claims (12)

1. A turning tool holder adapted to be supported on a tool rest, the tool holder carrying a cutting tool and having a projecting cut limiting device which engages the workpiece above the tool and thus limits the depth of cut of the latter.

2. A tool holder according to claim 1, comprising an elongate bar of rectangular section with an inclined bore adjacent the forward end in which the tool is adjustably secured and above which the cut limiting device projects forwardly over the tool.

3. A tool holder according to claim 1 or claim 2, wherein the cut limiting device is of inverted hooklike form, being secured to the tool holder at one end and at the other free end in use engaging the workpiece a short distance above and slightly rearwardly of the cutting edge of the tool.

4. A tool holder according to any one of the preceding claims, adapted to be supported on a tool rest in the form of a bar which extends parallel to the turning axis and along which is slidable a saddle providing a sliding guide forthe tool holder.

5. A tool holder according to any one of the preceding claims in an arrangement having a tool rest comprising a bar which extends parallel to the turning axis and along which is slidable a saddle providing a sliding guide for the tool holder, said saddle having a guideway along which the tool holder is advanced into cutting engagement with the workpiece.

6. An arrangement according to claim 5, wherein the tool rest is a cylindrical bar on which the sliding guide can pivot to vary the inclination of the tool holder and thus, for a given relative setting of the tool and cut limiting device, vary the depth of cut.

7. A tool holder or arrangement according to any one of the preceding claims, wherein the tool holder has a projecting follower for engagement with a profiled edge of a master such as a pattern or template, the contour shape of which is reproduced on the workpiece.

8. An arrangement according to claim 7, wherein said master is disposed below the tool rest and on the rear side thereof.

9. An arrangement according to claim 7 or claim 8, wherein said master is a replica of the workpiece to be turned and mounted between centres.

10. A tool holder or arrangement according to any one of claims 7 to 9, wherein the follower is mounted on the tool holder so as to be adjustable longitudinally thereof.

11. An arrangement according to claim 7, wherein the projecting follower comprises a bar fixed to the tool holder and having a free end projection which slides in a groove in the tool rest some distance from the tool holder.

12. A tool holder or arrangement thereof, substantially as hereinbefore particularly described with reference to the accompanying drawings.