DESCRIPTION

Field of invention ■

The invention relates to turning tools for use in turning wood, brass or aluminium. The invention is intended mainly for the D-I-Y (Do-It-Yourself) market and provides some facilities similar to that of a lathe.

Background of invention Machines for turning wood have generally include ^" a motor for turning a drive centre. An elongate piece of wood was supported at one end on the drive centre and at the other end on a centre of a tail stock. An adjustable stand for supporting a chisel could be located near to the turning wood material to enable the chisel to remove wood and give the turned shaped desired.

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Considerable skill and experience is required to hold the chisel so as to provide the desired shape with any degree of accuracy. If the chisel is held incorrectly, an operator may lose control over the chisel. The chisel may be wrenched from the operator's hand. Satisfactory operation also depends to a considerable extent on the proper sharpening of the chisel.

It is an object of the invention to provide a turning tool which is relatively easy to use, enables accurate shapes to be obtained, is relatively safe in operation, is easy to set up, and/or can be manufactured economically.

General description of invention

According to the invention there is provided a turning tool including a drive centre for turning a workpiece, a first elongate member, a tool arm angularly pivotable and slidable longitudinally with respect to the first member and a second elongate member parallel to the first and capable of being abutted by the tool arm. The tool arm is thus firmly supported even though it is movable radially and

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longitudinally of a workpiece. The second elongate member limits movement of the tool arm towards the workpiece and can be used by the operator to guide him in providing a cylindrical turned surface.

In a particularly convenient and simple construction the first and second elongate members are mounted at one end in a motor housing containing a motor for rotating the drive centre and support a tail stock between them at the other end, the position ^{" "} of the tail stock being adjustable lengthwise of the first and second members. The turning tool accordingly can occupy a small space and its construction can be kept very simple. The tool arm may be straight and mounted on a pair of superposed ^" rods. However, preferably the tool arm has a general U-shape so as to extend peripherally around the workpiece. The two elongate members can then be arranged horizontally. The arm so shields the workpiece to some extent and can be controlled by both the operator's hands if necessary. Conveniently tne tool arm mounts a tool holder.

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The tool holder in turn supports a tool bit for removing workpiece material using a negative rake. As a result of this arrang ment if an operator releases the tool arm the tool bit will be urged radially outward of the workpiece and will not dig in with possible risk of damage. Conveniently the tool holder has an adjustment knob for moving the tool bit towards or away from the workpiece. By adjusting the tool bit to the desired radius whilst using the abutment between the tool arm and second elongate member to provide a fixed tool arm arm attitude, it is possible to turn cylindrical surfaces of varying sizes relatively accurately.

Conveniently the tool bit is ^* formed by an exchangeable plate secured to a tool bit support member. The tool bit can then be ground in an easy manner to give a sharp edge without the need to maintain a heel as on a chisel.

Suitably the motor housing has a means for securing it to a work top and the elongate members are rods cantilevered outwards from the housing. Advantageously the motor in the

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housing is a low voltage DC motor so as to provide considerable power at a relatively low cost.

. Advantageously the motor housing contains a single casting or casting assembly for supporting on one side the elongate members and the drive centre and on the other side the motor with a gear transmission arrangement from the motor to the drive centre being supported in the casting or casting assembly. The use of a single casting or assembly contributes be a rigid construction and greatly facilitates assembly in manufacture.

DRAWINGS

Figure 1 shows an end view Of a turning tool of the invention with a tail stock removed-r- • Figure'2 shows a section along line A-A in

Figure 1;

Figures 3 and 4 show enlarged views of a spindle support member and tool bit for use in the turning tool of Figure 1 and Figure 2; o Figures 5 and 6 show a front view and longitudinal section respectively of a tool holder for mounting the spindle support member and tool bit of Figures 3 and 4;

Figures 7 to 18 show different views and sections of detailed designs for the motor housing, tool arm and tool stock of a turning tool according to the invention.

Description of preferred embodiment

With reference to the Figures, a turning tool 2

includes a housing 4 containing a motor 42 for rotating a drive centre 6- A irst bar 8 and a second bar 10 are cantilevered outwards from the housing 4. The bar 8 supports a tool arm 12, pivotably and slidably. The motor 42 (Figure 2) is mounted on a casting 14 which further supports reduction gears 16 and 18 and a drive sha t 20 or the drive centre 6.

The bars 8 and 10 slidably support between them a tail stock 24 carrying a tail stock centre 26 axially aligned with the drive centre 6. The tail stock 24 can be clamped in any desired position longitudinally of. ^" the • bars 8 and 10.

The tool arm 12 ( ^" Figures 1, 3, 4, 5 and 6) -has secured thereto a tool holder 28. The tool holder 28 contains a rotatable adjustment knob 32. The adjustment knob 32 has an internal thread engaging a square sectioned spindle support member 34 non-rotatably and slidably supported by the tool holder 28. A tool bit 30 can be secured to the spindle support member 34 by a grub screw at 36 (Figure 4) . Thus by turning the adjustment knob 32, the spindle 34 and the tool bit 30 can be moved radially with respect to the workpiece supported between the drive centre 6 and the tail stock centre 26. It can be seen in Figure 1 that the tool bit 30 is at a negative rake with respect to any

workpiece supported between the centres 6 and 26.

The housing 4 has a means for receiving a clamp 38 so that the housing and thereby the turning tool 2 ca be secured to a work top shown at 40.

The turning tool is of simple and cheap construction.

The motor 42 may be a 12 Volt DC motor which is conne to the mains by means of a transformer. Thus the equipment is electrically safe. The operator has considerable control over the turning operation and can turn both shapes and parallel surface with considerable accuracy and ease.

The turning tool may be modified for working on materials other than wood by changing the tool bit

36. after removing the grub screw/ Plastic, brass and aluminium may be turned in a similar way using the negative rake. The angle of the tool bit 30 could changed to provide a positive rake for turning other materials such as metal. This may however require general strengthening of the turning tool as the turning forces will be greater.

With reference to Figures 7 to 11, the housing 4 (Figure 7) can be made from two moulded components and include a main housing moulding 50 (shown in section in Figure 9) and a motor cover moulding 52 (shown in side elevation in Figure 8) . The cover

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moulding 52 is connected to the moulding 50 by clips 54 engaging in recesses 56. The main moulding 50 (shown in side elevation in Figure 9) has a recess 58 for the clamp.38 and an aperture 59 for an ON/OFF switch 60. The main moulding 50 further has internally (see Figure 9 and Figure 11 which shows the moulding in plan) posts 62 for fastening a casting and is provided' with holes 64 for a number of shafts projecting from the casting.

With reference to Figures 12 and 13, the casting 66 (see Figure 12) has three lugs 68 for receiving ^' screws for connecting to the posts 62; a wiring anchor projection 70; a pair of a semi-circular recesses 72 for receiving the bars 8 and 10 which are held in position by a clamping 5 plate (not shown) fastened by a screw into hole 74; a hole 76 for the motor output gear and shaft; a circular recess 78 for the drive centre shaft 20. The final assembly is illustrated by Figure 13.

With reference to Figure 14, (a side view of the tool o a-*-" ¹¹¹ 12) , a tool arm can be moulded and support the various components discussed previously.

With reference to Figures 15 to 18, the tail stock 24 (Figure 15) has a lower part 82 (seen from above in Figure 17 and from the side in Figure 16) and an upper 5 part 84 (seen from below in Figure 18) . The parts 62

and 84 are pulled together by a belt 86 passing throug a slot 87 in the part 82. A handle 88 is fitted in a recess 89 in the part 84 for limited travel to release and apply the pulling force so as to enable th tail stock 24 to be shifted on the bars 8, 10 without risk of over tightening of the tail stock 24 on the rods 8, 10. The tails stock centre 26 is supported a ball 90 (Figure 16) retained behind a bush 92. A centre 26 can be retained in the bush 92 and pushed against the ball 90 without giving rise to friction wi material of the tail stock which may be of moulded plastics material.

The components shown and described with reference to Figure 7 to 18 can be combined into a single turning tool joined by the bars 8, 10 as described generally with reference to Figures 1 to 6.

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