GB2192145A - Jaws for a lathe chuck - Google Patents

Abstract

A jaw (6) for a chuck comprises a support member or main jaw (5) locatable so as to be adjustably displaceable within a guide or jaw guideway of a chuck (1) and carrying or being adapted to receive a re-orientatable jaw or auxiliary jaw (6) which has regions for provision of or is provided with a plurality of workpiece engaging faces and is locatable on said support member or main jaw (5) in a plurality of different positions so as to present a plurality of workpiece-engaging regions which are each abutable against a workpiece (4). The auxiliary jaw may be hexagonal as shown or alternately, circular square, triangular semi-hexagonal or semi circular in form. <IMAGE>

Description

SPECIFICATION Improved jaws of a lathe chuck The present invention relates to an improved jaw or jawsforthechuckofalathe or like machinetool.

Various types of lathe chucks are known such as three-jawed chucks and four1awed chucks and the present invention is primarily, although not essentially, concerned for use with a three-jawed chuck.

Chucks are supplied with jaws which are referred to as "hard jaws" and are formed with steps, normally three, so as to be adjustable to engage different diameterworkpieces. For more precisework, and where softer materials are used, what are termed "soft jaws" have to bepurchasedwhereinthesurfacesof the jaws which engage the workpiece are especially machined for each specific diameterworkpiece and thus with different diameter workpieces, separate machining operations are required in each case and eventuallythejaws becometooshortforfurtheruse and such remaining stubs have to be replaced by new jaws.Such procedure is both time-consuming and expensive and, furthermore, such known jaws in the form of elongate, displaceable members sometimes do not meet accurately in the centre so as to enableverysmall objects to be held accurately.

It is an object of the present invention to provide improved jaws for a chuck.

According to the present invention an improved jawfor a chuck comprises a support member or main jaw locatable so as to be adjustably displaceable within a guide or jaw guideway of a chuck and carrying or being adapted to receive a re-orientatable jaw or auxiliaryjawwhich has regions for provision of or is provided with a plurality ofworkpiece engaging faces and is locatable on said support member or main jaw in a plurality of different positions so asto present a plurality of workpiece-engaging regions which are each abutable against a workpiece.

It will be appreciated that the provision of such a re-orientatable or auxiliary jaw permits the various regions orfaces of the jaw to be differently machined so asto accommodate and accurately abut differently dimensioned workpieces and that by reorienting each re-orientatable jaw or auxiliary jaw, a specific machined face or seat may be retained in an inoperative dispositionforsubsequent possible reutilisation should an appropriately dimensioned workpiece have to be subsequently machined.Thus the auxiliary jaw or jaws, as they will be referred to subsequentlyfor simplicity but not restrictively, enable particular machined faces or seats to be re tained for subsequent possible use and permit the avoidance of duplication of machining operations and, furthermore, may be readily removed and stored for possible subsequented use and may be readily replaced by a new auxiliary jaw. The provision of such auxiliary jaws on a conventional chuck or as a modification of a conventional chuck also avoids the main or master jaws from being machined away to unusable stubs and thus provides economies in this respect and also in that such auxiliary jaws might also be regarded as comprising sacrificial components.

Whilst any suitably shaped auxiliary jaw may be utilised, such as triangular or even circular or such as a combination of semi-hexagonal and semi-circular, it has been found preferable for the auxiliaryjawto be of hexagonal shape when viewed in plan - part icularlywhen used with a th ree-jawed chuck- since the hexagons meet accurately towards the centre.

Forfour-jawed chucks, a suitable and correspondingly suitable shaped jaw might be utilised, such as square jaws.

A suitable jaw aligning means is provided on each supporting member or main jaw and will be such as to accurately locate each auxiliary jaw in each of its various positions of use and preferably comprises a projection which is engageable in a plurality of recesses in each orientatable jaw to accurately align the jaw in each of its intended position of use. Locating means are also provided for each re-orientatable jaw to ensure the jaw is not displaced during any machining or holding operation and preferably include means such as undercut or inclined surfaces of the auxiliary jaws which are displaceable to interlock with a mounting blockorlikememberorportionon the supporting memberormainjawtoholdthe auxiliary jaws in accurate position against movement relative to its support.

Additional securing means, such as a threaded bolt may be provided for securing each auxiliary jaw and will extend through a passage in each auxiliary jaw and have a head engageable with a recessed shoulderoftheauxiliaryjawandengageinatapped bore in the support member or main jaw to hold at leastthe auxiliary jaw and possibly also the jaw locating means on the main jaw.

The aligning and/or locating means may either be machined on the main jaw or secured orfixed thereon by any known means.

When each re-orientatable jaw or auxiliaryjaw is in the form of a hexagonal member, aligning slots or passages will preferably be machined extending rad ially from the centre thereof and through the apex of each corner and a correspondingly dimensioned aligning projection will be formed or located on the main jaw, preferably remote from the workpiece engaging area, and be dimensioned to fit within the aligning passages so that accurate alignment and location may be achieved during indexing of the hex agonallyshaped auxiliary jaw. Similar aligning passages may be provided in differently shaped auxiliary jaws.

It will thus be appreciated that the advantages of the improved jaw arrangement and a chuck incorporating such improved jaw arrangement according to the invention resides in the possibility of provision of increased engaging surface area of the auxiliary jaw with aworkpiece resulting in a greater wrapround of the workpiece being machined which is particularly useful for materials such as aluminium.

Furthermore, the arrangement according to the present invention makes it easierto hold very small objects, especially in the preferred arrangements ofthe hexagonally shaped jaws, since the jaws may meet accurately in the centre. Additionally, the auxiliary jaws, which are preferably hexagonal, are indexable so that a variety of holdings can be kept on one chuck and, as mentioned previously, the auxiliary jaws may be readily replaced thus enabling a variety of holdings to be stored or may be re-machined thus possibly avoiding or minimizing the main jaws from being constantly machined away.

The present invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 7 is a perspective view illustrating a conventional three-jawed chuck wherein the three jaws may have their ends appropriately machined so as to provide an appropriate seat to accurately engage a centrally located workpiece; Figure 2 is a schematic perspective view il lustrat- ing a three-jawed chuck incorporating a preferred embodiment of the jaw arrangement according to the present invention; Figure 3 is a schematic elevation of two auxiliary jaws of Figure 2 illustrating two of the three hexagonal auxiliary jaws having cornersurfacesthereof machined to form shoulders for receiving a central workpiece;; Figure4is a plan viewfrom below of a hexagonal auxiliary jaw of Figures 2 and 3 showing radial aligning passages for indexing and being machined through each corner, and this view indicating in broken-lines inclined undercut surfaces which inter Iockwith cooperatively shaped locating means on the main jaw; Figure 5 is a schematic side illustration of a main jaw carrying aligning means and locating means thereon; and Figure 6 is a plan view of the main jaw of Figure 5.

In Figure 1 a known three jawed chuck 1 is illustrated with a jaw adjustment aperture 2 for receiving adjustment key (not shown) and three adjustable jaws 3 of conventional design holding a workpiece 4 centrallythereof. The ends of the jaws 3 which abut the workpiece 4 wi II have been previously suitably machined in known manner so as to provide an accurate seatfortheworkpiece 4. With each new dim ension of workpiece, the ends of the jaws 3 have to be re-machined and thus eventually become so short they have to be replaced. Details of the chuckguideways and adjustment means for the jaws are well known and it is thus not considered necessarythat such be described in any more detail.

The preferred embodiment according to the present invention is illustrated in Figures 2 to 6 and in Figure 2 a chuck body 1 of generally conventional design carries three adjustable supporting members or main jaws Son each of which a hexagonal reorientatable or auxiliary jaw 6 is located by locating means 8, 12 as will be described hereinafter. The shaping of the bottom of jaw 5 shown in Figure 5 is to receive the drive threads ofthe chuck adjustment means (notshown).Aworkpiece4is held bythe three jaws 6 which may be regarded as "soft jaws" .

Each ofthethree jaws 6 is hexagonally shaped and has a central passage having an enlarged upper recess 6' therein for receiving a threaded bolt 7 for securing purposes, with the head lying within recess 6 so as notto obstruct wo rkpiece 4. Each jaw 6 hasa substantially flat top surface, apart from a recess for access to the head of bolt 7, whilst the bottom surface has a recess 10 formed therein and having inclined sidewalls 10' of hexagonal disposition corresponding to the hexagonal outer shape ofthe jaw 6 whilst the upper surface 10" of the recess 10 is substantially planar. Each side wall 10' extends from the lowermost defining edge of the recess 10 upwardly and outwardly.

The locating means are each in the form of a shaped member 8 fixed on the upper surface of jaw 5 and have front surfaces 8" and 8"' which are inclined u pwardly and outwardly correspondingly to the inclined surface 10' of the jaw so that when the jaw6 is placed over the locating means 8 with one pas- sageway 11 locating with minimal clearance overthe aligning projection 12 and when jaw 6 is moved to the left in Figure 5, the inclined surface 8" co-operates with inclined surface 10' ofthejaw 6so as to inter- lock jaw 6 with member 8 and thus locate on the jaw Sin accurate position. The ends 5' of the jaw 5 are inclined as illustrated in the plan view of Figure 6 so as not to project beyond the sides of jaws 6 and avoid being damaged whilst enabling jaw proximity in the centre.Surface 8"' does not come into contact with hexagon jaw 6 but is an escape route for any swarf.

Six radial aligning passages 11 are provided, each extending symmetrically through a corner of each hexagonal jaw 6 and are provided so as to accurately co-operate with an elongate rectilinear aligning projection means 12 secured or formed on the centre line of the main jaw 5.

Thus, in use, the jaws 6 are each located with two corners thereof centrally located of the jaw and, initially, one cornerwill be machined to provide a seat 13 forworkpiece 4. When it is necessary to hold a workpiece of a different dimension, the bolts 7 are removed and the chucks 6 are displaced radially in wardlyto permit such to be removed from the jaw 5.

Each jaw 6 is then rotated or, re-orientated so that another pair of corners lie on the central line of each jaw 5 and again positioned and held accurately by the locating means 8 and the aligning means 12 together with bolt 7 whereupon another seat 13 (of different dimension) can be machined. Thus, each jaw may provide six differently dimensioned seats for workpieces and whilst of course further machining of a seat may take place, the utilisation ofthedif- ferentcorners enables re-use of a particulardimensioned seat should further machining of a workpiece of the previously machined dimension be necessary. Furthermore, the use of hexagonally shaped jaws facilitates the holding of very small objects as the hexagons meet accurately in the centre and, furthermore, a larger surface of the jaw may engage a workpiece i.e. a greaterwrap-round is available in certain machining instances which is most useful for machining materials such as aluminium.

Furthermore, since the hexagonal auxiliary jaws are indexable, a variety of holdings can be kept on one chuck.

Itisto be appreciatedthatthevariousmodi- fications and changes proposed in the introduction ofthis specification can be incorporated into the specific embodiment as modifications thereof.

Furthermore, the arrangement according to the present invention may be provided as an adaption to existing conventional chuck jaws bysecuringtheloc- ating means and aligning means on the known jaws to hold the re-orientatable or auxiliary jaws accord ing to the present invention (which are preferably hexagonal jaws) accurately in position. However, it is the primary intention that the supporting members forthe re-orientatable jaws according to the present invention be provided as dedicated purpose-built components. Other shapes of the components ofthe invention may be utilised as desired to provide the advantageous features of the invention.

In use, and when boring out, the bolts 7 are left slightly undone until the hexagons are clamped togetherwhereupon they arethen tightened. The retaining action of the bolts is secondary to that achieved with the cooperation of the undercut and the bolts are only used to stop the hexagon slipping during changing of the workpiece. The undercut can be considered to be shaped as a "V" to help accurate location.

Claims (14)

1. An improvedjawforachuckcomprisesasup- portmemberor main jaw locatableso asto be adjustably displaceable within a guide or jaw guideway of a chuck and carrying or being adapted to receive a re-orientatable jaw or auxiliary jaw which has re gions for provision of or is provided with a plurality ofworkpiece engaging faces and is locatable on said supportmemberormainjawina plurality of different positions so as to present a plurality of workpiece-engaging regions which are each abutable against a workpiece.

2. A jaw as claimed in claim 1, in which the re orientatablejaw is triangular or circular or a combination of semi-hexagonal and semi-circular, or preferably of hexagonal shape when viewed in plan.

3. A jaw as claimed in claim 1 for a fourjawed chuck, in which square jaws are provided.

4. A jaw as claimed in any of claims 1 to 3, in which a jaw aligning means is provided on each supporting member or main jaw to accurately locate each re-orientatable or auxiliary jaw in each of its various positions of use.

5. A jaw as claimed in claim 4, in which the jaw aligning means comprises a projection which is engageable in a plurality of recesses in each reorientatable jaw or auxiliary jawto accurately align the jaw in each of its intended position of use.

6. A jaw as claimed in any of claims 1 to 5, in which locating means are provided for each reorientatable jaw or auxiliaryjawto ensure the jaw is not displaced during any machining or holding operation.

7. A jaw as claimed in claim 6, in which each locating means includes undercut or inclined surfaces of each re-orientatable or auxiliary jaw which are displaceableto interlockwith a mounting blockorlike member or portion on the supporting memberor main jaw to hold the auxiliary jaws in accurate position against movement relativeto its support.

8. A jaw as claimed in any of claims 1 to 7, in which additional securing means is provided, such as a threaded bolt for securing each re-orientatable orauxiliaryjawand extends through a passage in each re-orientatable or auxiliary jaw and has a head engageable with a recessed shoulder of the auxiliary jaw and engages in a tapped bore in the support member or main jaw to hold at least re- orientatable or auxiliary jaw.

9. A jaw as claimed in claim 8, in which the additional securing means also holds the jaw locating means on the main jaw.

10. A jaw as claimed in claims4and/or 6, in which the aligning and/or locating means are machined on the main jaw or secured orfixedthereon by any known means.

11. A jaw as claimed in any of claims 1 to 10, in which aligning passages are provided in each reorientatable or auxiliaryjawto ensure accurate alignment.

12. A jaw as claimed in claim 11, in which each re-orientatable jaw or auxiliary jaw is in the form of a hexagonal member and aligning slots or passages are machined extending radially from the centre thereof and through the apex of each corner and a correspondingly dimensional aligning projection is formed or located on the support member or main jaw, preferably remote from the workpiece engaging area, and is dimensioned to fit within the aligning passages so that accurate alignment and location is achieved during indexing of the hexagonally shaped auxiliary jaw.

13. A plurality ofjaws as claimed in any ofclaims 1 to 12 whenever incorporated in a chuck.

14. An improved jaw or an improvedchucksub stantiallyas herein described with reference to the accompanying drawings.