WO1988007904A1

WO1988007904A1 - Collet/adapter assembly

Info

Publication number: WO1988007904A1
Application number: PCT/US1988/001191
Authority: WO
Inventors: Ralph E. Ammendolia; Bruce A. Hartman
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-04-13
Filing date: 1988-04-13
Publication date: 1988-10-20
Anticipated expiration: 1989-10-13
Also published as: JPH02503076A

Abstract

Collet/adapter assembly (22) which can be connected to a lathe spindle (20) for rotation therewith without removing the lathe chuck (24) as has heretofore been required. The assembly includes: a spindle nose (44) which is bolted to the face of the lathe chuck (24), a collet (42) which is slidably mounted in the spindle nose (44) and can be drawn into that component to bias the collet jaws (48, 50, 52) together and thereby secure a tool or workpiece (31) in the collet (42), and a collet adapter (46) which is fixed to the collet (42) and to the drawbar (40) operated slide (32) of the lathe chuck (24) so that the collet (42) can be drawn into the spindle nose (44) to bias the collet jaws (48, 50, 52) together as aforesaid by rectilinearly displacing the lathe drawbar (40). A spindle nose-mounted chuck closer (106) may be employed to bias the collet jaws (48, 50, 52) together in place of the spindle nose. This allows the collet/adapter assembly (22) to accept collets of larger jaw diameter than they could otherwise accommodate.

Description

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COLLET/ADAPTER ASSEMBLY

TECHNICAL FIELD OF THE INVENTION The present invention relates to a novel, improved assembly for coupling a draw-in collet to the spindle of a lathe.

BACKGROUND OF THE INVENTION Workpieces are commonly supported for rotation with the spindle of a lathe by bolting the workpiece to the face.plate of the lathe or by mounting the workpiece in a chuck or in a draw-in collet.

Heretofore, it has been necessary to remove the lathe chuck in order to use a collet. This is time consuming and therefore undesirable. The changeover from chuck to collet typically takes one hour or longer. The changeover from chuck to draw-in collet is also dangerous. Lathe chucks may weigh as much as 80-90 pounds, and the person making the changeover must lean over the lathe to dismount and remove the chuck. Consequently, there is a substantial risk that one may injure himself in making the chuck-to-collet changeover. It is significant, in this respect, that many if not most modern lathes have overhanging components which make it impractical to hoist the chuck in a vertical direction. Thus, it is almost always necessary that the chuck be manually removed from the lathe on which it is mounted. In the conventional arrangement, the collet is retracted into a cooperating adapter by the drawbar of the lathe on which the collet is installed to collapse the jaws of the collet and secure a tool or workpiece in it. An important disadvantage of this conventional work-supporting system for lathes is that the collet jaws can be collapsed to the extent that the collet will be sucked into the lathe mechanism when the lathe drawbar is retracted unless a tool or workpiece is first installed in the collet. This can damage or destroy the collet and/or damage the lathe.

SUMMARY OF THE INVENTION

We have now invented and disclosed herein a novel collet/adapter assembly which allows a draw-in collet to be operatively coupled to a lathe spindle without the downtime and risk of injury involved in making the heretofore required changeover from chuck to collet. This novel assembly, which allows the collet to be mounted without removing the lathe chuck, includes a - conventional draw-in collet, a spindle nose, and a collet adapter.

The collet is slidably mounted in a bore extending from end-to-end through the spindle nose, and the spindle nose is fastened to the mounted lathe chuck. Thus, it will rotate with the latter but cannot move longitudinally.

One end of the spindle nose through bore is tapered to match the external, tapered configuration of the jaw end of the collet. Consequently, by displacing the collet in the spindle nose, the collet jaws can be biased or squeezed together to secure a tool or a workpiece in the collet.

The opposite end of the collet is threaded into the collet adapter. This adapter is in turn threaded into the rectilinearly displaceable slide provided in the lathe chuck to move the radially extending jaws of the chuck in and out. Rectilinear movement of the chuck jaw-operating slide is effected by a conventional, typically hydraulically operated drawbar. Consequently, by displacing the lathe drawbar, the collet of our novel collet/adapter assembly can be drawn into the spindle nose of the assembly to bias its jaws together and thereby secure the tool or workpiece in the collet.

Another feature of our novel collet/adapter assembly is a set of integral stops on the spindle nose. These stops lie in the paths of movement of the chuck jaws and limit the retraction of those jaws when the collet/adapter assembly is installed. The limiting of chuck jaw retraction in turn limits the travel of the chuck slide to which the collet adapter is connected. This keeps the collet from being drawn into the spindle nose far enough to be damaged when the drawbar of the lathe is retracted to draw the collet into the spindle nose.

In many cases the jaw end of the collet is bored out to make it capable of holding larger tools or workpieces than it otherwise ould. Thereafter, the collet may be removed and then reinstalled as circumstances warrant.

A further important feature of our invention, in this respect, is a novel collet/adapter design which positively and precisely locates the collet in the same position — both longitudinally and angularly about its longitudinal axis — each time the collet is reinstalled. This is important because it insures that there is the same, identical, concentric relationship between the longitudinal axis of the workpiece-receiving bore and the axis of rotation of the collet each time the collet is replaced. As a consequence, workpieces secured in the collet can be machined to much closer tolerances than would be the case if there were a random relationship between the axis of the workpiece-receiving bore in the collet and the axis of rotation of that component and a consequent lack of concentricity between those two axes.

Concentricity is particularly important when the part being turned is turned end-for-end in the process so that it can be machined to the same diameter from end-to-end.

Absent concentricity, the diameters of the two separately machined segments of the workpiece might not match within acceptable limits; and the axial centerlines of those segments might not be aligned with an acceptable degree of accuracy.

Yet another important practical advantage of our invention is that a single spindle nose will accept collets of varying types and sizes.

In this respect, the novel spindle noses we have disclosed herein will also accept a chuck closer.^' his makes the collet/adapter assembly capable of accepting collets with jaw diameters (or face sizes) limited only by the capacity of the chuck closer.

OBJECTS OF THE INVENTION

From the foregoing, it will be apparent to the reader that the primary object of the present invention is the provision of novel, improved collet/adapter assemblies which make it possible to mount a draw-in collet on a lathe and to rotatably couple the collet to the lathe spindle without removing a previously mounted chuck from the lathe. A related and also important object of our invention resides in the provision of novel collet/adapter assemblies which allow a collet to be mounted and coupled to a lathe spindle without the downtime or risk of injury involved in the changeover from chuck to collet heretofore required to mount a draw-in collet on a lathe.

Another important and primary object of the present invention resides in the provision of novel improved systems for so mounting draw-in collets on lathes as to protect the collet from damage in the event that the collet is drawn into a cooperating component to bias its jaws together without first mounting a tool or workpiece in the chuck.. Still another important object of our invention is the provision of collet/adapter assemblies which permit workpieces mounted in the collet to be machined to close tolerances by insuring that the collet is located in the same precise position relative to the adapter each time it is installed in that adapter. And yet another important object of our invention resides in the provision of assemblies and systems as defined in the preceding objects which are capable of accepting collets of different types and sizes including collets with jaw diameters so large that the collet jaws cannot be closed by the collet supporting spindle nose.

A still further and also important, but more specific, object of the invention resides in the provision of collet/adapter assemblies which include: a collet, a collet supporting spindle nose which is adapted to be fixed to a lathe chuck for rotation therewith at a fixed longitudinal location and which is so constructed that displacement of the collet relative thereto will result in the collet jaws being biased toward each other to secure a tool or workpiece therebetween, and a collet adapter for so connecting the collet to the drawbar of the lathe that displacement of the drawbar will result in the collet being drawn into the spindle nose to bias the collet jaws toward each other and into gripping relationship with the tool or workpiece mounted therein. Other important objects and features and additional advantages of our invention will be apparent to the reader from the foregoing and the appended claims and as the ensuing detailed description and discussion proceeds in conjunction with the accompanying drawing..

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a fragmentary view of a metal turning lathe equipped with a collet/adapter assembly in accord with the principles of the present invention; FIG. 2 is an exploded view of certain components of the lathe and the components of the collet/adapter assembly;

FIG. 3 is a longitudinal, vertical section through the collet/adapter assembly;

FIG. 4 is an end view of the collet/adapter assembly; and

FIG. 5 is a view similar to FIG. 3 of a collet/adapter assembly which embodies the principles of the present invention and which is equipped with a chuck closer, thereby making the assembly capable of accepting collets with larger jaw diameters than it otherwise could. DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawing, FIGS. 1 and 2 depict a lathe 20 equipped with a collet/adapter assembly 22 constructed in accord with, and embodying, the principles of the present invention. The collet/adapter assembly is employed to support bar stock workpieces or the like and tools such as drill bits, for example.

As discussed above, one of the main attributes of collet/adapter assembly 22 is that it allows a collet to be employed without first removing chuck 24 from lathe 20 as would be necessary if a conventional changeover from a chuck-to-collet type of support were being made. Chuck 24 is bolted to, and rotates with, the spindle mounted face plate 26 of lathe 20. The chuck includes a circularly sectioned housing 28 in which a number (typically three) of radially displaceable jaws 30 are mounted. Jaws 30 are displaced inwardly to clamp a workpiece or tool 31 (see FIG. 1) therebetween and outwardly to release the workpiece or tool. The radial displacement of chuck jaws 30 is effected by a slide 32. This slide is rectilinearly displaceable in a bore 34 through chuck housing 28 in the directions indicated by double-headed arrow 36 in FIG. 2.

The rectilinear translation of slide 32 is effected by an also rectilinearly displaceable, hydraulically operated drawbar 40.

Chucks of the character just described are available from Oku a Machinery Works, Ltd. For that reason and because the details of chuck 24 are not part of the present invention, they will not be eluded to further herein except as is necessary to an understanding of the present invention.

Turning now to FIGS. 1, 2, and 3, the collet/adapter assembly 22 employed to equip lathe 20 with a tool or workpiece supporting collet includes a conventional draw-in collet 42, a collet supporting spindle nose 44, and a hollow, cylindrical, collet adapter 46.

Collet 42 is of conventional construction. It includes three, identical, equiangularly related spring jaws .48, 50, and 52 (see FIG. 4) which can be biased or squeezed toward each other to grip and secure the selected workpiece or tool 31 in the central opening 54 between the jaws. The opposite end 58 of the collet is threaded as is shown in FIG. 2. As is best shown in the same Figure and in

FIG. 3, collet 42 is slidably installed in a central bore 60 which extends from end-to-end through spindle nose 44.

Matching external and internal tapers 62 and 64 are formed at the cooperating, outer ends of collet 42 and spindle nose 44, respectively. Consequently, by displacing collet 42 relative to spindle nose 44 in the direction indicated by arrow 66 in FIG. 2 to draw the collet into spindle 44, collet jaws 48, 50, and 52 are squeezed or biased toward each other by spindle nose 44. This results in the collet jaws gripping the tool or workpiece 31 installed in central collet opening 54 to secure the tool or workpiece in the collet. Jaws. 8...52 may be bored out to increase the diameter of opening 54 and thereby make collet 42 capable of accepting workpieces (or tools) or larger diameter. As is best shown in FIGS. 2-4, the barrel 68 of the spindle nose 44 in which bore 60 is formed is surrounded by two, adjacent, integral, annular flanges 70 and 72. Flange 70 is dimensioned to fit snugly in, and be seated against the bottom 74 of, a complementary, circular recess 76 which is formed in, and opens onto the exposed face 78 of, chuck housing 28. This accurately centers spindle nose 44 and the collet 42- mounted in that spindle nose in chuck 24. The barrel 68 of spindle nose 44 is mounted in the recess 76 at the free or exposed end of lathe chuck 24. The spindle nose is fixed to lathe chuck 24 by equiangularly spaced, threaded fasteners 80. These fasteners extend through apertures 82 in spindle nose flanges 70 and 72 into internally threaded apertures 84 which are formed in the casing 28 of lathe chuck 24.

As is best shown in FIG. 4, three flats 86, 88, and 90 are formed on spindle nose flange 72. These flats (see FIG. 1) are located in the paths of movement of the three, radially displaceable jaws 30 of chuck 24. Consequently, spindle nose flange 72 limits the inward movement of the jaws and, consequentially, the rectilinear displacement of slide 32 and drawbar 40 in the direction shown by arrow 92 in FIG. 2. This is an_. important feature of our invention as will become apparent hereinafter.

Referring again to FIGS. 2 and 3, the inner end 58 of collet 42 is threaded into an internally threaded aperture 93 in collet adapter 46. That component has a hollow, cylindrical configuration.

As is best shown in FIG. 3, there is a radial shoulder 94 in adapter 46 at the inner end of threads 93. As collet 42 is threaded into adapter 46, -10- its inner end 58 engages shoulder 94; and the shoulder locks the collet in the same rotational or angular relationship relative to the adapter each time the collet is installed. For example, the point identified by reference character 95 in FIG. 3 lies 45° above the lower edge 96 of the shank 97 of collet 42. The engagement between collet shank end 58 and adapter shoulder 94 insures that this same relationship will be established between the lowest shank edge 96 and point 95 each time collet 42 is threaded into adapter 46. This insures that the longitudinal axis of the workpiece receiving bore 54 drilled or otherwise machined in collet 42 and the axis of rotation of the collet will be concentric each time collet 42 is installed in collet adapter 46. As a consequence, a workpiece mounted in bore 54 will rotate about the same identical axis as the collet and can therefore be machined to closer tolerances than would otherwise be the case. External threads 98 are formed on collet adapter 46. The adapter is threaded into an internally threaded aperture 99 in the rectilinearly translatable slide 32 of lathe chuck 24. This couples the collet adapter to the chuck slide for movement therewith as the slide is rectilinearly translated along the bore 34 in the chuck casing 28 in which the slide is housed.

Threads 99 are not present in the slide of a conventional lathe chuck and must therefore be formed to accommodate collet/adapter assembly 22. This, however, is a minor undertaking, especially in the relation to the problems that are solved by the utilization of the collet/adapter assembly. Drawbar 40 is also coupled to slide 32 to effect this rectilinear translation of the slide. The connection is furnished by external threads 100 on the drawbar and cooperating, internal threads 102 in slide 32.

Thus, with the components of collet/adapter assembly 22 assembled as shown in FIG. 3 and the assembly coupled to chuck 24 as shown in FIG. 1, displacement of drawbar 40 to the left as shown by arrow 92 will displace slide 32 and collet adapter 46 in the same direction. This draws collet 42 into spindle nose 44 because the latter is maintained in a longitudinally fixed position by chuck 24.

As collet 42 is thus drawn into spindle nose 44, collet jaws 48, 50, and 52 are squeezed toward each other by the sliding engagement between the tapered external surface 62 on the collet and the cooperating tapered internal surface 64 ^'in the spindle nose. This securely retains the workpiece or tool 31 in the collet. As discussed above, the flats or stops 86, 88, and 90 on the flange 72 of spindle nose 44 limit the retraction of chuck slide 32 and drawbar 40 as the latter is displaced in the direction of arrow" 92 to draw collet 42 into spindle nose 44 and thereby secure a workpiece or tool in the collet. Absent this important feature, collet 42 could be drawn into spindle nose 44 to the point where the tapered end 62 of the collet would move into the cylindrical section 104 of the bore 60 through spindle nose 44. That would damage or even destroy the collet and/or damage the spindle nose. We also pointed out above that spindle nose 44 is constructed to accept chucks of various type — for example, round, square, and hexagonal collets. Further ore, as shown in FIG. 5, a conventional chuck closer 106 with internal threads 108 can be threaded on the external threads 110 formed on the barrel 68 of spindle nose 44. This allows collet type step chucks 114 with jaw diameters larger than that of the tapered, jaw closing bore section 64 in spindle nose 44 to be employed in collet/adapter assembly 22.

For example, the assembly 116 illustrated in FIG. 5 is designed to accept collets with a face diameter D of approximately two inches. By employing an appropriate chuck closer 106, however, collets with face (or jaw) diameters of up to six inches can be employe in the same assembly without modifying any of the assembly components. Chuck closer 106 is a hollow, cylindrical component. When threaded onto spindle nose 44, it is located longitudinally relative to the latter for proper jaw closing cooperation with step chuck 114 by the radial shoulder 117 furnished by the flange 72 on spindle nose 44. The engagement of the inner end 107 of chuck closer 106 with shoulder 117 also rotationally locks the chuck closer and spindle nose together.

The bore 118 through the free or exposed end of chuck closer 106 is tapered as indicated by reference character 120 to match the tapered jaws 122 of step chuck 114. Consequently, as the chuck is drawn into the chuck closer by the above-discussed displacement of lathe drawbar 40 to the left as indicated by arrow 92 in FIG. 2, the collet jaws 122 are squeezed toward each other by the sliding engagement between the tapered external surfaces 124 of step chuck 114 and the cooperating internal tapered surface 120 in chuck closer 106. This securely retains the workpiece (or poεεibly tool) being mounted in the bore 126 surrounded by the jaws 122 of the chuck.

Though not specifically apparent from FIG. 5, the taper of the surface 120 in chuck closer 106 is so related to the taper of the surface 64 in spindle nose 44 that surface 120 will be engaged by and squeeze together step chuck jaws 122 before the tapered surface 128 at the forward end of step chuck shank 130 seats against the tapered surface.64 in spindle nose 44. This insures that chuck closer 106 will operate properly. At the same time, this arrangement provides a sliding fit between step chuck 106 and spindle nose 44 that rigidly supports the step chuck without freedom to wobble in the forward end of the spindle nose. The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description: and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

CLAIMSWhat we claim as our invention is:

1. The combination of: a lathe which has a rotatable chuck with movable jaws and jaw operating means which is displaceable to effect opening and closing movements of said jaws, a collet having jaws, a collet supporting means which is fixed to said chuck for rotation therewith and so interacts with said collet that displacement of said collet relative to its supporting means results in the collet jaws being biased toward each other to grip a tool or workpiece therebetween, and means for so connecting said collet to said jaw operating means that the displacement of said jaw operating means will displace said collet relative to its supporting means to bias said collet jaws together as aforesaid.

2. A combination as defined in claim 1 wherein said collet supporting means is fixed directly to said rotatable chuck for rotation therewith.

3. The combination of: a lathe which has a rotatable chuck with movable jaws and jaw operating means which is displaceable to effect opening and closing movements of said jaws, a collet having jaws, a collet supporting means which is fixed to said chuck for rotation therewith, chuck closing means which is affixed to said collet supporting means for rotation therewith and so interacts with said collet that displacement of said collet relative to its supporting means and the chuck closing means results in the collet jaws being biased toward each other to grip a tool or workpiece therebetween, and means for so connecting said collet to said jaw operating means that the displacement of said jaw operating means will displace said collet relative to its supporting means to bias said collet jaws together as aforesaid.

4. The combination of: (a) a lathe which includes a rotatable chuck with movable jaws and jaw operating means which is displaceable to effect opening and closing movements of said jaws, and (b) a collet/adapter assembly for rotatably fixing a tool or workpiece to said chuck for rotation therewith, said collet/adapter assembly comprising: a collet having jaws which are biasable toward each other to grip a tool or workpiece therebetween; a spindle nose fixed to said chuck for rotation therewith, said spindle nose supporting and so interacting with said collet that displacement of said collet relative to said spindle nose will effect the biasing together of said jaws; and means so connecting said collet to the jaw operating means of the lathe that displacement of said jaw operating means will effect the aforesaid displacement of said collet relative to said spindle nose and the consequent biasing together of said collet jaws.

5. The combination of: (a) a lathe which includes a rotatable chuck with movable jaws and jaw operating means which is displaceable to effect opening and closing movements of said jaws, and (b) a collet/adapter assembly for rotatably fixing a tool or workpiece to said chuck for rotation therewith, said collet/adapter assembly comprising: a collet having jaws which are biasable toward each other to grip a tool or workpiece therebetween; a collet supporting spindle nose fixed to said chuck for rotation therewith; a chuck closer which is fixed to said spindle nose for rotation therewith and which so interacts with said collet that displacement of said collet relative to said spindle nose and said chuck closer will effect the biasing together of said jaws; and means so connecting said collet to the jaw operating means of the lathe that displacement of said jaw operating means will effect the aforesaid displacement of said collet relative to said chuck closer and said spindle nose and the consequent biasing together of said collet jaws.

6. A combination as defined in claim 5 wherein there are internal threads in said chuck closer and external threads on said spindle nose for fixing the chuck closer to the spindle nose.

7. The combination of: (a) a lathe which includes a rotatable chuck with radially displaceable jaws, a slide which is rectilinearly displaceable to effect displacement of said jaws, and a rectilinearly displaceable drawbar for effecting the rectilinear displacement of said slide; and (b) a collet/adapter assembly for rotatably fixing a tool or workpiece to said chuck for rotation therewith, said collet/adapter assembly comprising: a collet having a tapered external configuration provided by jaws which are biasable toward each other to grip a tool or workpiece therebetween; a spindle nose means fixed to said lathe chuck for rotation therewith, said spindle nose having an internal bore in which said collet is slidingly received and one end of said bore being tapered to match the external taper on the collet, whereby said collet jaws can be biased toward each other by drawing said collet into said spindle nose; and a collet adapter fixed to the end of the collet opposite the jaws, said adapter including means for operatively connecting said adapter via the slide of said chuck to said drawbar, whereby rectilinear displacement of said drawbar will draw said collet into said spindle nose to bias said collet jaws toward each other as aforesaid.

8. A combination as defined in claim 7 wherein the spindle nose has a transversely extending flange, wherein there are apertures in said flange, and wherein there are fasteners extending through said apertures and fixing said spindle nose to said chuck.

9. A combination as defined in claim 7 wherein said collet adapter is a unitary cylindrical member, wherein said adapter is threaded onto said opposite end of said collet, and wherein the means for fixing the collet adapter to the lathe drawbar comprises external threads on the collet adapter and matching internal threads in the slide of the lathe chuck.

10. A combination as defined in claim 7 wherein there is an annular recess in and operating onto the outer face of said chuck and wherein there is a complementary annular flange on said spindle nose for centering said spindle nose relative to the axis of rotation of the chuck.

11. The combination of: (a) a lathe which includes a rotatable chuck with radially displaceable jaws, a slide which is rectilinearly displaceable to effect displacement of said jaws, and a rectilinearly . displaceable drawbar for effecting the rectilinear displacement of said slide; and (b) a collet/adapter assembly for rotatably fixing a tool or workpiece to said chuck for rotation therewith, said collet/adapter assembly comprising: a collet having a tapered external configuration provided by jaws which are biasable toward each other to grip a tool or workpiece therebetween; a spindle nose means fixed to said lathe chuck for rotation therewith, said spindle nose having an internal -18- bore in which said collet is slidingly received; a chuck closer fixed to said spindle nose for rotation therewith, said chuck closer also having a bore in which the collet is slidingly received and one end of said chuck closer bore being tapered to match the external taper on the collet, whereby said collet jaws can be biased toward each other by drawing said collet into said chuck closer; and a collet adapter fixed to the end of the collet opposite the jaws, said adapter including means for operatively connecting said adapter via the slide of said chuck to said drawbar, whereby rectilinear displacement of said drawbar will draw said collet into said chuck closer to bias said collet jaws toward each other as aforesaid.

12. A combination as defined in claim 11 wherein there are internal threads in said chuck closer and external threads on the spindle nose for fixing the chuck closer to the spindle nose and wherein there are stop means on the spindle nose for positioning said chuck closer relative to said spindle nose and for preventing rotation of said chuck closer relative to said spindle nose.

13. The combination of: a lathe which has a rotatable chuck with movable jaws and a jaw operating means which is displaceable to effect opening and closing movements of said jaws, a collet having j,aws which are biasable toward each other to grip a tool or workpiece therebetween, a collet supporting means which so interacts with said collet that displacement of said collet relative to its supporting means results in the collet jaws being biased toward each other to grip the tool or workpiece therebetween as aforesaid, means for so connecting said collet to said jaw operating means -19- that displacement of said jaw operating means as aforesaid will displace said collet relative to said supporting means to bias said collet jaws toward each other as aforesaid, . and means for limiting the inward movement of said chuck jaws and, consequentially, the magnitude of the displacement of said collet relative to said supporting means that can be effected by the aforesaid displacement of the jaw operating means.

14. A combination as defined in claim 13 which has means for fixing said collet supporting means directly to said lathe chuck for rotation therewith.

15. A combination as defined in claim 13 which includes a spindle nose fixed to the lathe chuck for rotation therewith and wherein said collet supporting means is similarly fixed to said spindle nose.

16. A collet/adapter assembly which comprises: a collet having a tapered external configuration provided by jaws which are biasable toward each other to grip a tool or workpiece therebetween; a spindle nose which is adapted to be fixed to a lathe chuck or lathe component for rotation therewith, said spindle nose having an internal bore in which said collet is slidingly received and one end of said bore being tapered to match the external taper on the collet, whereby said jaws can be biased toward each other by drawing said collet into said spindle nose; and a collet adapter fixed to the end of the collet opposite the jaws, said collet adapter including means for connecting said adapter to a means which can be actuated to draw said collet into said spindle nose as aforesaid.

17. A collet/adapter assembly as defined in claim 16 wherein said collet adapter is a unitary cylindrical member, wherein said adapter is threaded onto said opposite end of said collet, and wherein the means for fixing the collet adapter to the collet displacing means comprises external threads on the collet adapter.

18. A collet/adapter assembly as defined in claim 16 wherein the spindle nose has a transversely extending flange and wherein there are apertures in said flange through which fasteners can be installed to fix said spindle nose to the lathe component with which said spindle nose is adapted to rotate.

19. A collet/adapter assembly as defined in claim 16 wherein said collet and said adapter have means which cooperate to precisely locate the collet in the same relationship to the adapter with respect to the location of the collet about the longitudinal axis of the adapter each time the collet is assembled to the adapter.

20. A collet/adapter assembly as defined in claim 19 wherein said cooperating means comprise internal threads in the adapter, external threads on one end of the collet, and a shoulder at the inner end of the internal threads against which the threaded end of the collet is designed to seat when the collet is fixed to the adapter by threading the collet into the adapter.

21. A collet/adapter assembly which comprises: a collet having a tapered external configuration provided by jaws which are biasable toward each other to grip a tool or workpiece therebetween; a spindle nose which is adapted to be fixed to a lathe chuck or lathe component for rotation therewith, said spindle nose having an internal bore in which said collet is slidingly received; a chuck closer fixed to said spindle nose for rotation therewith, said chuck closer also having an internal bore in which the collet is slidingly received and one end of said chuck closer bore being tapered to match the external taper on the collet, whereby said jaws can be biased toward each other by drawing said collet into said chuck closer; and a collet adapter fixed to the end of the collet opposite the jaws, said collet adapter including means for connecting said adapter to a means which can be actuated to draw said collet into said chuck closer as aforesaid. .

22. A collet/adapter assembly as defined in claim 21 wherein there are internal threads in said chuck closer and external threads on said spindle nose for fixing the chuck closer to the spindle nose.

23. A collet/adapter assembly as defined in claim 22 wherein there are stop means on said spindle for positioning said chuck closer longitudinally with respect to said spindle nose and for preventing rotation of said chuck closer relative to said spindle nose.

24. A collei/adapter assembly as defined in claim 21 wherein said collet adapter is a unitary cylindrical member, wherein said adapter is threaded onto said opposite end of said collet, and wherein the means for fixing the collet adapter to the collet displacing means comprises external threads on the collet adapter.

25. A collet/adapter assembly as defined in claim 21 wherein the spindle nose has a transversely extending flange and wherein there are apertures in said flange through which fasteners can be installed to fix said spindle nose to the lathe component with which said spindle nose is adapted to rotate.

26. A collet/adapter assembly as defined in claim 21 wherein said collet and said adapter have means which cooperate to precisely locate the collet in the same relationship to the adapter with respect to the location of the collet about the longitudinal axis of the adapter each time the collet is assembled to the adapte .

27. A collet/adapter assembly as defined in claim 26 wherein said cooperating means comprise internal threads in the adapter, external threads on one end of the collet, and a shoulder at the inner end of the internal threads against which the threaded end of the collet is designed to seat when the collet is fixed to the adapter by threading the collet into the adapter.