Method and apparatus for forming thin discs

Abstract

A method of supporting a workpiece on a fixture, the workpiece having a first surface and an opposite second surface, and an aperture positioned at a center of the first surface and extending from the first surface to the second surface the fixture having a first end, an opposite second end, and a center portion, the center portion comprising a supporting surface, the second end being adapted to be mounted in a lathe, the supporting surface comprising an annular recess, the annular recess accommodating a supporting medium, the second surface of the workpiece being in intimate contact with the supporting medium, the method comprising the steps of: (i) mounting the fixture in the lathe; (ii) locating the aperture on the first end of the fixture; and (iii) securing the workpiece on the fixture, with the second surface of the workpiece being coplanar with the supporting surface of the fixture.

Claims

1. A fixture for supporting a workpiece in a lathe, the fixture comprising: a body having a first end, an opposite second end, and a centre portion, the first end comprising a spigot extending from the centre portion, the second end being adapted to be mounted in the lathe and having a larger diameter than the spigot, the centre portion comprising a backing disc, the backing disc having a supporting surface and a single annular recess, the single annular recess accommodating a supporting medium, the supporting medium providing the supporting surface, the plane of the supporting surface being normal to the axis of the spigot; and a clamping element, securable on the spigot to thereby clamp a workpiece against the supporting surface.

2. The fixture as claimed in claim 1, wherein the spigot comprises a threaded portion, and the clamping element threadingly engages with the threaded portion.

3. The fixture as claimed in claim 1, wherein the backing disc is integrally formed with the fixture.

4. The fixture as claimed in claim 3, wherein the workpiece is adhesively bonded to the supporting medium.

5. The fixture as claimed in claim 3, wherein the supporting medium is a composite resin.

6. The fixture as claimed in claim 1, whereby the workpiece has a first surface and an opposite second surface, and wherein the supporting surface completely accommodates the second surface of the workpiece.

7. The fixture as claimed in claim 6, wherein the diameter of the supporting surface is larger than the diameter of the second surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) There now follows a description of an embodiment of the invention, by way of non-limiting example, with reference being made to the accompanying drawing:

(2) FIG. 1 shows a schematic sectional view of a fixture according to an embodiment of the invention.

(3) It is noted that the drawing may not be to scale. The drawing is intended to depict only typical aspects of the invention, and therefore should not be considered as limiting the scope of the invention.

DETAILED DESCRIPTION

(4) Referring to FIG. 1, a fixture according to an embodiment of the invention is designated generally by the reference numeral 100.

(5) The fixture 100 comprises a body 120 and a damping element 150. The body 120 comprises a first end 122, a second end 124 and a centre portion 126.

(6) In the present arrangement, the body 120 and the damping element 150 are each formed from a steel alloy material. In alternative arrangements, the body 120 and the clamping element 150 may be formed from another metal or metal alloy.

(7) In a further alternative, the body 120 and the clamping element may be formed from a composite material.

(8) The first end 122 comprises a spigot 130 extending from the centre portion 126, the spigot 130 having an axis 132. The second end 124 of the body 120 is adapted to be mounted in a lathe (not shown). In the present arrangement, the second end 124 of the body 120 is formed as a cylindrical stub extending from the centre portion 126 in an opposite axial direction to the spigot 130.

(9) In an alternative arrangement the second end 124 of the body 120 may be formed with a hexagonal circumferential surface to more easily facilitate its accommodation within a lathe.

(10) The centre portion 126 comprises a backing disc 140. In the present arrangement the backing disc 140 is formed as a separate component from the body 120. Alternatively, the backing disc 140 may be integrally formed with the body 120. The backing disc 140 is formed from a steel alloy. In alternative arrangements the backing disc 140 may be formed from another metal or metal alloy, or from a composite material.

(11) The backing disc 140 has a locating hole 141 and a supporting surface 142. In use, the locating hole 141 is positioned over the spigot 130 such that a plane 144 of the supporting surface 142 is normal to the axis 132 of the spigot 130.

(12) The damping element 150 is securable on the spigot 130 to thereby clamp the workpiece 110 against the supporting surface 142. In the present arrangement, the clamping element 150 is formed as a nut with an internal threaded portion which threadingly engages with a threaded portion 134 of the spigot 130.

(13) In an alternative arrangement, the clamping element 150 may comprise any conventional mechanical clamping element, such as an over-centre clamp or a tapered collet clamp.

(14) The backing disc 140 comprises an annular recess 146 on the supporting surface 142. The annular recess 146 is filled with a supporting medium 148 such that the supporting medium 148 comprises the supporting surface 142.

(15) In one arrangement the supporting medium 148 is a wax compound. Alternatively, the supporting medium may be a composite resin material.

(16) In use, the fixture 100 is used to support a workpiece 110 having a first surface 112, an opposite second surface 114, and an aperture 116 positioned at a centre of the first surface 112.

(17) The annular recess 146 of the backing disc 140 is filled with the supporting medium 148, and the backing disc 140 is positioned over the spigot 130, with the backing disc 140 located at the centre portion 125 of the body 120, and with the spigot 130 extending through the backing disc 140.

(18) The workpiece 110 may then be located over the spigot 130 with the spigot 130 extending through the aperture 116 such that the second surface 114 of the workpiece 110 is coplanar with the supporting surface 142.

(19) The clamping element 150 is then secured to the spigot 130 to clamp the workpiece 110 to the backing disc 140.

(20) The fixture 100 may then be located in a lathe and the first surface 112 of the workpiece machined by the cutting tool(s) (not shown) of the lathe.

(21) The foregoing description of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously, many modifications and variations are possible. Such modifications and variations that may be apparent to a person of skill in the art are included within the scope of the invention as defined by the accompanying claims.