GB2045123A - Mandrels - Google Patents

Abstract

The invention relates to the manufacturing of metal strip from an annular feedstock. An annular mandrel is carried by a headstock spindle of a lathe and includes a tapered bore 5 dimensionally complementary to the headstock spindle; cutting tools 2 protrude from the radially outer peripheral surface of the mandrel and are so positioned that they cut axial grooves in the internal surface of an annular feedstock pressed axially onto the mandrel. <IMAGE>

Description

SPECIFICATION Precision mandrel for strip peeling feedstocks This invention relates to the manufacture of metal strip by peeling a layer of metal from the periphery of a rotating annular feedstock. More especially, the invention concerns apparatus for and methods of internally gripping an annularfeedstock during a peeling operation.

Processes for producing metal strip are known which involve peeling a surface layer from a rotating metal feedstock mounted on a headstock spindle of a lathe by controllably feeding a cutting tool into the peripheral surface of the feedstock and coiling the peeled strip under conditions of controlled tension to produce a peeled strip product of dimensional tolerance comparable with that of cold rolled strip.

Feedstock for strip peeling conveniently comprises a disc having a parallel sided bore concentric with the axis of the disc. The disc may be produced by one of several different routes. To produce such a disc shaped feedstock a scaled product possessing a dimensionally inexact surface finish and profile is produced by one of several known routes. This must then be machined to produce a precise bore, end faces and peripheral dimensions required for the peeling operation. Any reduction in the machining required would significantly reduce the overall cost of producing the feedstock.

Existing systems for internally gripping feedstocks to sustain the large torsional and radial forces occasioned during peeling involve the use of internally expanding headstock spindles, thermal interference fitting or axial clamping by mechanical or hydraulic means. These systems require that the feedstock, as mentioned above, has a precisely machined bore to ensure that the feedstock is clamped onto the lathe headstock spindle with a sufficient degree of stability. The present invention sets out to minimise the machining operation required to be undertaken prior to peeling of an annular feedstock.According to the present invention in one aspect thereis provided an annular mandrel for internally gripping an annularfeedstock to be peeled by a peeling process, the mandrel having a tapered bore and a plurality of spaced cutting tools protruding from its radially outer peripheral surface.

According to the present invention in another aspect, apparatus for manufacturing metal strip from an annular feedstock comprises an annular mandrel carried by a headstock spindle of a lathe, the mandrel including a tapered bore dimensionally complimentary to the headstock spindle, and cutting tools protruding from its radially outer peripheral surface. The cutting tools are so positioned that they cut axial grooves in the internal surface of an annular feedstock pressed axially onto the mandrel.

According to the present invention in still another aspect a method of manufacturing metal strip from an annular feedstock includes the steps of pressing the feedstock onto an annular mandrel formed with a plurality of spaced cutting tools upstanding from its radially outer peripheral surface to cut axial grooves in the internal peripheral surface of the annular feedstock corresponding to the shape and configuration of the tools and locating the mandrel about a headstock spindle of a lathe, the bore of the mandrel and the headstock spindle being dimensionally precisely complimentary.

A hardenable fluid (e.g. plaster) may be introduced into the spaces formed between the opposed surfaces of the mandrel and the feedstock. For this purpose a series of passageways may be formed within the body of the mandrel.

The assembly of the mandrel and feedstock may be clamped on to the headstock spindle by an hydraulic means to provide a degree of prestress.

Prior to peeling, the surface of the feedstock may be skimmed by a lathe mounted tool to provide an improved peripheral surface finish and concentricity with the bore of the mandrel. The invention will now be described by way of example with reference to the accompanying diagrammatic drawings in which Figure 1 is a perspective view of the mandrel in accordance with the present invention; Figure 2 is a section taken along the line ll-ll of Figure 1; and Figure 3 is an end view of a feedstock to be peeled, mounted on the mandrel illustrated in Figures 1 and 2.

The mandrel illustrated in the drawing comprises an annular steel body 1 having three carbide cutting tools 2 set in axially extending grooves formed in the radially outer peripheral surface of the body 1. A circumferential groove 10 is also formed in the outer periphery of the body 1. The tools 2 stand proud of the mandrel surface and are each supported within the respective groove by a hardened block 3 formed with a central relief 4. The bore 5 of the mandrel is precisely tapered to compliment accurately the dimensions of the headstock spindle of the lathe on which the mandrel is to be mounted in use.

Figure 3 shows an annular feedstock 6 assembled on the mandrel. The feedstock 6 comprises a hot-worked steel ring produced by one of several known routes. These routes include burning or trepanning from a steel slab, or rolling to round, cutting to length, upset forging and piercing followed possibly by ring rolling. The ring is assemblied onto the mandrel in its black condition (i.e.

unmachined) following descaling by acid pickling or shot blasting.

Assembly is accomplished by pressing the mandrel in the direction indicated by arrow A into the bore of the feedstock using an hydraulic press (not shown).

During the pressing operation, the mandrel is guided along a path concentric with the bore of the feedstock. The central reliefs 4 reduce the pressing force required during assembly. As the mandrel is pressed into the feedstock, the carbide tools 2 cut grooves into the inner periphery of the feedstock to locate the feedstock firmly on the mandrel.

Following assembly, the circumferential groove 10 and the spaces 7 which remain between the opposed surfaces of the mandrel and the feedstock are filled with a hardenable fluid, such as plaster, to provide a fully rigid assembly. The fluid is pumped into the spaces 7 through passageways 8 formed in the mandrel.

The assembly of the feedstock and mandrel is then mounted on the lathe to be used for the peeling operation by locating the precisely machined tapered bore of the mandrel over the complimentary tapered headstock spindle 9 of the lathe by an hydraulic press to provide a degree of prestress.

Before peeling, the peripheral surface of the feedstock is skimmed by a lathe-mounted cutting tool to ensure a suitable surface finish and concen tricitywith the rotational axis of the headstock spindle.

The actual peeling operation may be carried out using known techniques such as are described and illustrated in our U.K. Patent Specifications Nos.

1522507, 1522508 and 1522509.

During peeling, the feedstock is cooled con tinuouslyto avoid thermal expansion ofthefeed- stock relative to the mandrel and the edges of the feedstock are continuously premachined by a cutting tool located immediately upstream of the peeling station so that the peeling tool engages a constant feedstock width of uniform edge condition.

Peeling proceeds to a stage where a thin annular discard remains which is removed from the lathe with the mandrel. Finally, the discard is removed from the mandrel by slitting across its width at two or more locations so that the discard and the hardenable filler can be removed with a minimum of force.

By the invention described above, black feedstocks having nominal bore diameters which lie within the circumscribing circle containing the tool edges can be securely mounted onto the headstock mandrel of a peeling lathe. Advantages which accrue from the invention include significant reductions in feedstock preparation costs resulting from reduced or nil machining prior to peeling.

Claims (11)

1. Apparatus for manufacturing metal strip from an annularfeedstock comprising an annular mandrel carried by a headstock spindle of a lathe, the mandrel including a tapered bore dimensionally complimentary to the headstock spindle, and cutting tools protruding from its radially outer peripheral surface.

2. Apparatus as claimed in claim 1 wherein the cutting tools are set in equi-spaced axially extending grooves formed in the outer circumference of the mandrel.

3. Apparatus as claimed in claim 1 or claim 2 wherein a circumferential groove is formed in the periphery of the mandrel.

4. A method of manufacturing metal strip from an annular feedstock including the steps of pressing the feedstock onto an annular mandrel formed with a plurality of spaced cutting tools upstanding from its radially outer peripheral surface to cut axial grooves in the internal peripheral surface of the annular feedstock corresponding to the shape and configuration of the tools and locating the mandrel about a headstock spindle of a lathe, the bore of the mandrel and the headstock spindle being dimensionaily precisely complimentary.

5. A method as claimed in claim 4 including the additional steps of introducing a hardenable fluid into the spaces formed between the opposed surfaces of the mandrel and the feedstock.

6. A method as claimed in claim 5 wherein the hardenable fluid is introduced into the aforesaid spaces through a series of passageways formed within the body of the mandrel.

7. A method as claimed in claim 5 or claim 6 wherein hardenablefluid is also introduced into a circumferential groove formed in the outer periphery of the mandrel.

8. A method as claimed in any one of claims 4 to 7 wherein, the assembly of the mandrel and feedstock is clamped onto a headstock spindle by an hydraulic means to provide a degree of prestress.

9. A method as claimed in any one of claims 4 to 8 wherein, prior to peeling, the surface of the feedstock is skimmed by a lathe mounted tool to provide an improved peripheral surface finish and concentricity with the bore of the mandrel.

10. Apparatus for manufacturing metal strip substantially as herein described with reference to the accompanying drawings.

11. A method of manufacturing metal strip substantially as herein described with reference to the accompanying drawings.