Keyless chuck

Abstract: A keyless chuck (10; 301) comprises a jaw housing (28; 311) with jaws (32; 333, 335, 337) which are slidably mounted in guideways (40; 319, 321, 323) between a rearward opened position and a forward closed position. A jaw thrust member (34; 345) is coupled to the jaws and is slidably mounted in the jaw housing to apply a thrust force to the jaws and to maintain the jaws in the same relative axial location. A nut (42; 355) is fixed to the jaw housing and has a threaded opening (46; 357) coaxial with the chuck axis (Ax). A threaded spindle (48; 305) is engaged in the nut opening and is movable forwardly to apply clamping force to the jaws and rearwardly to remove clamping force. The jaws may be spring biased forwardly to a closed position (self-centering) and thus not movable responsive to movement of the spindle. A lock mechanism (22, 104, 42; 309) is preferably provided to limit relative rotation between the nut and spindle to prevent the application of excessive clamping force and to limit removal of clamping force.

Description: The present invention relates to a chuck for releasably gripping a tool bit and, more particularly, to a keyless chuck which provides reliable bi-directional operation and can be hand-tightened and loosened on a tool bit and, further, which can selectively self-tighten in response to torque applied through the chuck. Various types of chucks are known for releasably gripping the shank portion of a tool bit. The common Jacobs-style chuck includes a nosepiece which contains gripping jaws and a rotatably mounted adjusting sleeve that is adjusted to cause the jaws to grip or release a tool bit. The adjusting sleeve includes axially extending gear teeth that are adapted to cooperate with a gear-type key to permit manual tightening and loosening of the jaws. The requirement for a separate key necessitates a minimum level of manual skill to effect proper tightening of the jaws to avoid any slippage between the tool bit and the jaws. Additionally, the tightening key represents another part which is subject to loss or wear. A number of drill chucks, known generically as keyless chucks, have been designed in an effort to eliminate the need for the tightening key. Some of these chucks are adapted to apply an initial, hand-tightening gripping force to the tool bit with the chuck self-tightening in response to torque applied through the tool bit and the chuck. Some of these keyless chucks have been provided with gripping jaws which toggle in response to the reaction torque encountered by the tool bit and still others have been provided with cam-like surfaces which contact and cooperate with the gripping jaws to increase the gripping force. It is important for any self-tightening keyless chuck to grip the tool bit in response to initial hand-tightening by the operator with sufficient gripping force to that the tool bit will not slip during either forward or reverse operation. It is also important that the chuck, as it self-tightens in response to applied torque, not over-tighten to the extent that the jaws effect local major surface crushing of the tool bit stem or cause a lock-up situation in which the chuck cannot be loosened. Over-tightening and lock-up are generally not encountered with power tools intended for the consumer market. However, where such keyless chucks are used on power tools intended for commercial or industrial market, the substantial torques provided by these tools can induce undesired over-tightening. Known chuck designs have used one-way ratchet type mechanisms to allow a chuck to self-tighten in response to increased torque applied through the chuck and the tool bit. These designs allow the chuck to self-tighten in a progressive manner so that the tool bit will be reliably gripped as the applied torque is increased and prevent loosening of the chuck as a consequence of reverse operation. For example, U.S. Pat. No. 4,213,623 to Rohm discloses a drill chuck that includes an adjusting sleeve rotatably mounted to a chuck body for adjusting the gripping force applied by jaws mounted within the chuck body. The adjusting sleeve and the chuck body are coupled together by a one-way pawl and ratchet assembly. As the chuck is tightened in response to rotation of the adjusting sleeve relative to the chuck body, the pawl incrementally ratchets to a new position to maintain the tightened condition of the chuck and when the chuck is driven in reverse, prevents unintentional counter-rotation of the adjusting sleeve and loosening of the gripping jaws. In another chuck, as disclosed in U.S. Pat. No. 3,506,277 to Harms, an adjusting sleeve is rotatably mounted upon a chuck body to allow tightening or loosening of the gripping jaws. The chuck body includes ratchet teeth formed on an axial end face. The teeth are engagable with a similar set of teeth on a user adjustable spring biased sleeve. The teeth interengage to allow rotation of the adjusting sleeve to tighten the grip on the tool bit but prevent counter-rotation that would tend to loosen the tool bit. While these chucks are reasonably effective for their intended purpose, the chuck operator does not have full control over the manner by which the adjusting sleeve is operated and, accordingly, these chucks lack optimum operation flexibility. Substantial improvement of keyless chuck design has been made in accordance with the disclosure of U.S. Patent No. 4,848,779-Wheeler et al. As disclosed in the Wheeler patent, to reduce internal operating friction within the chuck, a small area contact patch may be provided between a main spindle and a jaw thrust member. A locking mechanism may be provided for unidirectional or bi-directional locking the relative rotatability of a chuck adjusting sleeve and a jaw housing which together control adjustment of the chuck jaws. Also, the locking mechanism may be capable of being selectively disabled. The chuck may further include an inelastically deformable surface between a jaw guide and a nut for accommodating any accumulated manufacturing tolerances to provide a chuck having minimal run-out. Thus, US 4 848 779 discloses a chuck comprising: a jaw housing having a forwardly disposed opening to receive a bit, a central guideway, a plurality of jaw guideways and a longitudinal axis (A x ); a plurality of jaws slidably mounted in the jaw guideways between a rearward opened and a forward closed position; a carrier engaged with the jaws and slidably mounted in the central guideway for maintaining each jaw in the same relative axial location; a nut fixed to the jaw housing and having a threaded opening coaxial of the longitudinal axis; a threaded spindle engaged in the nut opening and movable forwardly to apply clamping force to the jaws and rearwardly to remove clamping force; a manually actuated locking member movable between (a) a locked position engaging the nut to limit the relative rotation of the spindle and nut and (b) an unlocked position disengaging the nut to permit relative rotation of the spindle and nut; a rear sleeve fixed to the spindle; said nut and locking member having teeth engaged in the locked position and disengaged in the unlocked position. In addition to the foregoing improvements, further basic advancements have now been discovered to simplify the loading and unloading of a bit, to reduce operating friction, to simplify and improve the lock mechanism and to limit run-out. These advancements may be used individually or in combination. According to the present invention we provide a chuck comprising: a jaw housing having a forwardly disposed opening to receive a bit, a central guideway, a plurality of jaw guideways and a longitudinal axis (A x ); a plurality of jaws slidably mounted in the jaw guideways between a rearward opened and a forward closed position; a carrier engaged with the jaws and slidably mounted in the central guideway for maintaining each jaw in the same relative axial location; a nut fixed to the jaw housing and having a threaded opening coaxial of the longitudinal axis; a threaded spindle engaged in the nut opening and movable forwardly to apply clamping force to the jaws and rearwardly to remove clamping force; a manually actuated locking member movable between (a) a locked position engaging the nut to limit the relative rotation of the spindle and nut and (b) an unlocked position disengaging the nut to permit relative rotation of the spindle and nut; a rear sleeve fixed to the spindle; said nut and locking member having teeth engaged in the locked position and disengaged in the unlocked position; characterized in that: said rear sleeve and locking member have an engaged tab and slot to limit the relative rotation of the rear sleeve and locking member, said slot having a width extending transverse to the longitudinal axis greater than the transverse width of the tab to permit a predetermined amount of relative rotation between the rear sleeve and locking member; and said tab and slot comprise an automatic tightener for tightening the jaws on a bit a predetermined amount when the spindle is driven, the bit is engaged with a workpiece and the locking member is in the locked position A jaw thrust member or carrier may be coupled to the jaws, slidably mounted in the jaw housing to apply a thrust force to the jaws and to maintain the jaws in the same relative axial location. A nut may be fixed to the jaw housing and have a threaded opening coaxial with the chuck axis. A threaded spindle may be engaged in the nut opening and is movable forwardly to apply clamping force on the jaws and rearwardly to remove clamping force. The forward end of the spindle may include a projection which engages the jaw thrust member through a small area contact patch to limit the operating friction contribution of the jaw thrust member and thus provide a chuck which can be readily hand-tightened by the user and self-tightened in response to torque transmitted through the chuck. For ease of servicing of the chuck, a removable retainer may be optionally provided to engage the spindle tip for permitting selective removal of the spindle from the nut. As disclosed in one embodiment, the jaws may be movable back and forth between a rearward opened position and a forward closed position by rearward and forward movement of the spindle or in accordance with one advancement disclosed in a preferred embodiment, may be biased forwardly to a closed position ("self-centering") and thus not movable responsive to movement of the spindle. The lock mechanism also optionally permits incremental self-tightening when in the locked position. A second optional means to provide incremental self-tightening when using the chuck is to size and space the two sets of teeth to permit (1) a first limited maximum amount of relative rotation between the nut and locking member in a first direction (tightening) to advance the spindle and (2) a second limited maximum amount of relative rotation between the nut and locking member in a second direction (loosening) to retract the spindle. The amount of relative rotation for self-tightening is greater than the amount of relative rotation for self loosening. The spacing of the teeth also insures that the sets of teeth reliably seat for locking. In accordance with the second self-tightening means, one set of teeth preferably has a stair step profile in the axial direction. The teeth of the second set of teeth are slidable relative to the first set of teeth from the crest of the top step to the valley adjacent to the bottom step and is engagable with the flank of the next adjacent tooth of the first set when the nut and spindle are relatively rotated to advance the spindle and is engagable with the flank of the bottom step when the nut and spindle are relatively rotated to retract the spindle. The keyless chuck may be assembled in such a way that the run-out of the finished chuck is minimal without use of machined parts (except for the spindle). For this purpose, an in elastically deformed interface may be provided between a jaw thrust member (or carrier) and the spindle. The keyless chuck can be disassembled for cleaning and servicing and re-assembled without loss of run-out. In order to provide coaxial alignment of the spindle and nut, the spindle may have a precision smooth walled section (outer diameter) mating with a precision smooth walled section (inner diameter) of the nut opening and have a threaded section mating with a threaded section of the nut opening. The coaxial alignment of the spindle and nut is determined by the mating interface of the smooth sections. The threads of the mating threaded sections are loosely meshed to control only fore and aft movement of the spindle through the nut without affecting the coaxial alignment. The spindle preferably is a one piece output spindle of a power tool on which the chuck is used. The chuck may further comprise a divider in the jaw housing for spacing and guiding movement of the jaws. A central guideway is defined by divider guide surfaces and jaw housing guide surfaces. The carrier has a hub guided by the central guideway and a plurality of spokes extending transversely from the hub and engaging respective ones of the jaws. In order that the invention can be better understood, embodiments will be described in greater detail by way of example by reference to the accompanying drawings in which:- Figure 1 is a side view of a keyless chuck mounted on an exemplary pistol-grip electric drill; Figure 2 is an enlarged cross-sectional view of keyless chuck of Figure 1, the chuck of the type designed to be threaded onto and removed from the drive spindle of the electric drill; Figure 3 is an exploded perspective of the keyless chuck of Figs. 1 and 2; Figure 4 is a cross-sectional view of a keyless chuck of the type designed to be integrally assembled with the electric drill, the jaws shown in a retracted position; Figure 5 is a cross-sectional view of the keyless chuck of Figure 4 with the jaws in an advanced position; Figure 6 is an end view of a jaw for gripping a tool bit; Figure 7 is a side view of the jaw shown in Figure 6; Figure 8 is a plan view of a jaw thrust member; Figure 9 is a cross-sectional view of the thrust member of Figure 8; Figure 10 is a view of the jaw thrust member of Figures 8 and 9 from the side opposite that shown in Figure 10; Figure 11 is a side view, in partial cross-section, of a main spindle; Figure 12 is an enlarged detailed view of the remote end of the main spindle of Figure 11 in engagement with the jaw thrust member of Figures 8, 9 and 10; Figure 13 is an end view of a chuck adjusting sleeve; Figure 14 is a side view, in cross-section, of the chuck adjusting sleeve of Figure 13; Figure 15 is an end view of the chuck adjusting sleeve from the side opposite that shown in Figure 13; Figure 16 is an end view of a chuck adjusting nut illustrating a set of teeth on the end surface; Figure 17 is a side view, in cross-section, of the chuck adjusting nut of Figure 16; Figure 17A is an isometric view of the chuck adjusting nut of Figs. 16 and 17; Figure 17B is a detailed view, in cross-section, of the chuck adjusting nut of Figure 17 taken along line 17B-17B of Figure 17; Figure 18 is an end view of a lock plate illustrating a set of teeth for selective interengagement with the teeth of the chuck adjusting nut illustrated in Figure 16; Figure 19 is a side view, in cross-section, of the lock plate of Figure 18; Figure 20 is an end view of the lock plate from the side opposite that of Figure 18; Figure 21 is a side view, in cross-section, of a control sleeve; Figure 22 is a detailed view of a first set of interengaging teeth for selectively locking the chuck; Figure 23 is a detailed view of a second set of interengaging teeth for selectively locking the chuck; Figure 24 is a detailed view of a third set of interengaging teeth for selectively locking the chuck; Figure 25 is an end view of a second embodiment of a control sleeve; Figure 26 is a side view, in cross-section, of the control sleeve of Figure 25; Figure 27 is a detailed view of a cam profile of the control sleeve of Figures 25 and 26; Figure 28 is an end view of a second embodiment of a lock plate for cooperation with the control sleeve of Figures 25 and 26; Figure 29 is a detailed view of a cam formation of the lock plate of Figure 28; Figure 30 is a detailed view illustrating the engagement of the cam profile of the control sleeve interengaging the cam formation of the lock plate of Figure 28; Figure 31 is an isometric projection of jaw assembly and chuck adjusting nut mounted on mandrels as part of the assembly method; Figure 32 is a detailed plan view of a rear surface portion of the jaw guide illustrating a plurality of deformable pyramids; Figure 33 is a side view of the surface shown in Figure 32; Figure 34 is a longitudinal cross-sectional view of a keyless chuck in accordance with a second embodiment of the invention with the jaws shown in a normally closed position; Figure 35 is a longitudinal cross-sectional view of the chuck of Figure 34 shown with a tool bit clamped within the jaws; Figure 36A is a transverse cross-sectional view of the chuck shown in Figure 34 taken along line 36-36A; Figure 36B is a transverse cross-sectional view of the chuck of Figure 34 taken along line 36B-36B; Figure 37A is a transverse cross-sectional view of the chuck shown in Figure 34 taken along line 37A-37A; Figures 37B and 37C are fragmentary cross-sectional views similar to Figure 37A and showing two operating positions of automatic tightener for the chuck shown in Figure 34; Figure 38A is a rear elevational view of a jaw divider for the chuck shown in Figure 34 taken along line 38A-38A of Figure 38B; Figure 38B is a longitudinal cross-sectional view of the divider shown in Figure 38A taken along line 38B-38B; Figure 38C shows a front elevational view of the divider shown in Figs. 38A and 38B viewed along line 38C-38C of Figure 38B; Figure 38D is a longitudinal cross-sectional view of the divider shown in Figure 38C taken along line 38D-38D; Figure 39A is a rear elevational view of a stop for the chuck shown in Figure 34; Figure 39B is a longitudinal cross-sectional view of the stop shown in Figure 39A taken along line 39B-39B; Figure 40A is a longitudinal cross-sectional view of a nut for the chuck shown in Figure 34; Figure 40B is a rear elevational view of the nut shown in Figure 40A taken along line 40B-40B; Figure 40C is a front elevational view of the nut shown in Figure 40A taken along line 40C-40C; Figure 40D is a fragmentary side elevational view of the nut shown in Figure 40B taken along line 40D-40D; Figure 41 is a side elevational view of a spindle for the chuck shown in Figure 34; Figure 42A is a longitudinal cross-sectional view of a locking sleeve for a lock assembly for the chuck shown in Figure 34; Figure 42B is a rear elevational view of the locking sleeve shown in Figure 42A taken along line 42B-42B; Figure 42C is a front elevational view of the locking sleeve shown in Figure 42A taken along line 42C-42C; and Figure 43 is a fragmentary longitudinal cross-sectional view of the deformable interface between the spindle and stop for the chuck shown in Figure 34. The accompanying drawings illustrate two primary embodiments of the keyless chuck and together with the description serve to explain the principles of the invention; the first embodiment, however, does not show the automatic tightener which is an essential feature of the present invention. One embodiment of a keyless chuck is shown in Figures 1-33. A preferred embodiment, which is in accordance with the present invention, is shown in Figures 34-43. The first embodiment, chuck 10, is shown in Figures 1 and 2 mounted on an exemplary conventional pistol-grip electric tool 12 having a handle 14 and trigger control switch 16. As shown in Figure 1 and in the cross-sectional views of Figures 2 - 5, the keyless chuck 10 is defined about an axis A x and includes a jaw assembly 18, a chuck adjusting (or rear) sleeve 20, a control sleeve 22, and a main spindle 24. As shown in Figures 1 - 5, the jaw assembly 18 includes a jaw housing 28 formed as a body of revolution about the axis A x and includes an external serrated gripping surface 36 (Figure 1) to facilitate manual gripping and an interior bore 38 for accepting tool bits "T" of various diameters, as represented in dotted line illustration in Figure 3. The jaw guide 30 is received within internal openings in the jaw housing 28 to define three guideways 40 that each receive a respective jaw 32 for controlled movement between, respectively, the retracted and advanced positions of Figures 3 and 4. The angle of inclination between the guideways 40 and the axis A x is selected as a function the intended application. A 30 angle has been found to be suitable for most consumer and commerical applications. A smaller angle will provide increased clamping force. The jaws 32 are connected to a jaw thrust member 34 which, in turn, is coupled to the end of the main spindle 24, as explained more fully below. A chuck adjusting nut 42 is secured to the rearwardly facing end of the jaw assembly 18 by threaded fasteners 44 and includes a threaded internal bore 46 in engagement with complementary threads 48 of the main spindle 24 so that rotation of the jaw assembly 18 about the axis A x in the direction indicated in Figure 5 causes the jaws 32 to advance in the forward direction in their respective guideways 40 to grip a tool bit "T". Conversely, rotation of the jaw assembly 18 about the A x in the direction indicated in Figure 4 will cause the jaw assembly 18 to move to the right relative to the main spindle 24 and cause the jaws 32 to retract rearwardly in their respective guideways 40 to loosen the grip on a tool bit "T". The jaw housing 28 is preferably manufactured using powdered metal techniques and the jaw guide 30 is preferably manufactured from die-cast aluminum, zinc, or magnesium to present a rear face, as explained below, that is configured to deform during assembly of the chuck to accommodate any accumulated manufacturing tolerances and provide a finished chuck having minimal run-out. As shown in Figure 6 and 7, the jaws 32 each include an inclined outwardly facing surface 50 that bears against the guideway 40 in the jaw housing 28, a laterally extending boss 52 that is retained within a trackway (not shown) of jaw guide 30, and converging surfaces 54 and 56 that define an inwardly facing edge 58 that is adapted to engage the outside diameter surface of a tool bit "T" in the usual manner. The angle between the tool engaging surface 58 and the inclined surface 50 is equal to the guideway 40 angle as discussed above. Each jaw 32 includes a slot 60 adjacent its rearward end for receiving a portion of the jaw thrust member 34 so that the jaws 32 move as a unit in response to relative movement of the jaw thrust member 34. In the preferred embodiment, the jaws 32 are fine-flow blanked from rolled sheet stock having preformed inclined converging jaw surfaces that are coined to their finished dimension to define the surfaces 54 and 56 and the tool bit engaging edge 58. The configuration of the jaws 32 provides a keyless chuck 10 having a "zero capacity", that is, a chuck which can tighten upon small diameter tool bits "T". As shown in Figures 8, 9, and 10, the jaw thrust member 34 includes a central portion 62 and three radially outward extending and equi-spaced arms 64. Three upstanding sections 66 are provided between the arms 64 and define a central opening for engaging a projection at the end of the main spindle 24 as explained below. The inwardly facing surfaces of the upstanding sections 66 include a first surface 68 formed at a first diameter and second surface formed at a somewhat smaller diameter to define an inwardly facing rim 70, as shown in Figure 9, at the upper edge of the upstanding sections 66. As explained below, the upstanding sections 66 constrain the remote end of the main spindle 24 to engage a small-area contact patch 72 (dotted line illustration in Figure 8) to apply a thrust force against the jaw thrust member 34 which, in turn, applies the thrust against the jaws 34 to forcibly advance or retract the jaws 32. The main spindle 24, shown in partial cross-section in Figure 11, includes an enlarged diameter portion 74 at its rearward section having an internal threaded bore 76 for engaging the threaded drive spindle 26 (Figure 2) of the pistol-grip electric drill 12 in the usual manner. A reduced diameter axially extending section 78 carrying the threads 48 extends forwardly of the enlarged diameter section 74 and carries the threads 48 for engaging the chuck adjusting nut 42 as described above. The main spindle 24 includes a projection, indicated generally at 80, at its remote end for engaging the jaw thrust member 34. The projection 80 is defined by a reduced diameter portion 82, a somewhat enlarged rim 84, a conically tapered portion 86, and, lastly, a flat forwardly facing thrust surface 88. As shown in the enlarged detail of Figure 12 and in Figures 3 and 4, the projection 80 extends between the inwardly facing surfaces of the upstanding sections 66 of the jaw thrust member 34 with the outside diameter of the rim 84 of the projection somewhat larger than the inside diameter of the rim 70 of the jaw thrust member 34 so that the projection 80 must be forced between the upstanding sections 66 to allow the remote end of the projection 80 to 'snap' into engagement with the jaw thrust member 34 and thus releasably retain the two parts together while allowing relative rotation. The flat thrust surface 88 of the projection 80 is designed to bear against the small-area contact patch 72 (shown in Figure 8) of the jaw thrust member 34 to apply a thrust force to the jaw thrust member 34 and, in turn, apply the thrust force to the jaws 32 through the radially extending arms 64. In general, the contact patch 72 surface area is, of course, smaller than the cross-sectional area of the main spindle 24 (preferably 10 mm) and is preferably defined by a diameter dimension of 3mm or less. A contact patch area as small as possible is preferred. The remote end of the main spindle 24 is preferably induction hardened and the jaw thrust member may be made of powdered metal or preferably of precision blanked steel to provide contacting surfaces of sufficient hardness to accommodate the expected stresses. The provision of a small-area contact patch 72 between the remote end of the main spindle 24 and the jaw thrust member 34 contributes to a reduction of the internal friction in the keyless chuck 10 since any forces developed as a consequence of relative rotation between the main spindle 24 and the jaw thrust member 34 are located at relatively small radii from the axis A x and, accordingly, the torque and the contribution to the operating friction of the keyless chuck 10 will be low. The low operating friction of the chuck is further enhanced by the use of a small diameter spindle 24 compared with the outer diameter of the chuck. The spindle threaded portion preferably has an outer diameter of 8-10mm compared with a chuck outer diameter of 40-50mm. The large ratio enhances the leverage of the operator when tightening and loosening the jaws on a bit. The chuck adjusting sleeve 20, as shown in Figures 13, 14, and 15, includes an outer cylindrical section 90, an endwall 92 at is rearward end, and an inner cylindrical extension 94 that is formed coaxially with the operating axis A x of the chuck 10. The cylindrical section 90 includes three longitudinally extending slots 96 formed on its inner wall surface for engaging a locking plate, as explained below, and a series of longitudinal striations 98 on its exterior surface to facilitate manual gripping of the adjusting sleeve 20. A pair of parallel flats 100 are formed on the exterior surface of the adjusting sleeve 20 (Figure 13) adjacent the endwall 92 to facilitate gripping with a wrench or similar tool. The inner cylindrical extension includes a through bore 102 that accepts the enlarged diameter portion 74 of the main spindle 24 with an interference fit to secure the chuck adjusting sleeve 20 and the main spindle 24 together. If desired, additional locking devices, including various types of snap-rings and clips, may be used to assist in securing the components together. As shown in Figures 3 and 4, the main spindle 24 and the chuck adjusting sleeve 20 are secured to the drive spindle 26 with the reduced diameter portion 78 of the main spindle 26 in threaded engagement with the chuck adjusting nut 42 so that rotation of the jaw assembly 18 and the connected jaw adjusting nut 42 relative to the chuck adjusting sleeve 20 will advance or retract the jaws 32 in the jaw housing 28. In accordance with one feature, the keyless chuck 10 includes a locking mechanism which allows the chuck adjusting sleeve 20 and the jaw assembly 18 to be rotated relative to one another to allow hand-tightening of the chuck or self-tightening in response to torque transmitted through the chuck and which can be controlled by the operator to prevent counter rotation tending to loosen the chuck during reverse operation. Additionally, the locking mechanism can lock the chuck adjusting sleeve 20 and jaw assembly 18 from rotation in either direction and, in one form of the invention, can be selectively enabled or disabled by the operator. As shown in Figures 16 - 20, the lock mechanism includes the chuck adjusting nut 42, described above, and a lock plate 104. The chuck adjusting nut 42 (Figures 16 - 17B) includes the central threaded bore 46 that engages the reduced diameter portion of the main spindle 24, as described above, and a plurality of bores 106 through which the threaded fasteners 44 secure the chuck adjusting nut 42 to the jaw assembly 18. The bores 106 are distributed about the central axis of the chuck adjusting nut 42 in an unequal angular distribution so that the chuck adjusting nut 42 and the jaw assembly 18 can be assembled in a unique relationship to allow the chuck 10 to be disassembled, serviced, and reassembled without loss of the as-manufactured run-out, as described more fully below. In the preferred embodiment and as shown in Figure 16, the bores 106 are spaced apart by unequal angular spacings A1, A2, and A3 with the angular spacing A1 equal to 120, the angular spacing A2 equal to 115, and the angular spacing A3 equal to 125. The rearwardly facing end of the chuck adjusting nut 42 is provided with a circular pattern of radially aligned teeth 108 which cooperate with the lock plate 104 to effect the unidirectional or bi-directional locking function. As shown in Figures 17 and 17A, the tooth pattern is interrupted by clearance slots 106a for the threaded fasteners 44. Additionally and as shown in the detail of Figure 17B, annular rims 106b surround each of the bores 106 and project a small distance (e.g., 0.005 inch) from the forward face of the chuck adjusting nut 42. Preferably, to prevent relative rotation of nut 42 and jaw assembly 18, the annular rims 106b have a triangular profile with a forwardly pointing edge penetrating the deformable rear surface of the jaw assembly 18 during manufacture of the keyless chuck 10, as described below. The lock plate 104 (Figures 18-20) includes a circular, ring-like portion 110 with three tabs 112 extending radially outward from the circumferential edge of the circular portion 110. A series of radially aligned teeth 114 are provided on one face of the ring-like portion 110 and are designed to selectively engage the teeth 108 on the chuck adjusting nut 42 as explained below. The lock plate 104 is received within the chuck adjusting sleeve 20 with its teeth 114 facing forwardly and the tabs 112 received within the slots 96 (Figures 14 and 15) formed on the interior of the chuck adjusting sleeve 20. As shown in FIGURES 3, 4, and 5, a helical coil spring 116 is contained within the chuck adjusting sleeve 20 and resiliently biases the lock plate 104 in the forward direction. The control sleeve 22 is journalled on the outside diameter of the chuck adjusting nut 42 between the rear face of the jaw assembly 18 and the lock plate 104 and is freely rotatable about the chuck adjusting nut 42. As shown in Figure 21, the control sleeve 22 includes an extended tubular section 118 and a radially outward extending flange 120 at its forward end. The opposite end 122 of the tubular section 118 normally abuts the lock plate 104 which is then effective to resiliently bias the flange 120 against the rear face of the jaw assembly 18 in response to the force applied by the helical coil spring 116. As shown in Figures 4 and 5, the control sleeve 22 is normally biased in the forward direction by the spring-biased lock plate 104 to allow the teeth 114 on the lock plate 104 to engage the mating teeth 108 formed on the rearwardly facing end of the chuck adjusting nut 42. The control sleeve 22 is rotatably mounted on the chuck adjusting nut 42 and, as shown in solid and dotted line illustration in Figure 4, can be moved by the operator from a forward position against the biasing force of the spring 116 to a rearward position to disengage the teeth 114 of the lock plate 104 from the teeth 108 of the chuck adjusting nut 42. As explained below, the selection of the profile of the teeth 108 and 114 as well as the force applied by the spring 116 can be selected to control the chuck to fully lock the jaw assembly 18 from rotation relative to the chuck adjusting sleeve 20 in either the forward or reverse direction, to allow relative rotation in the forward direction only in response to hand tightening of the chuck as well as torque transmitted through the chuck, and to selectively enable or disable the locking function. Figure 22 illustrates a first tooth profile for the teeth 114 of the locking plate 104 and the teeth 108 of the chuck adjusting nut 42. As shown, each tooth includes a relatively steeply pitched flank 120, a relatively shallow pitch flank 122, and a flat crest 124. The lock plate 104 is resiliently urged downward in Figure 22 by the urging force of the spring 116 so that the teeth 114 and 108 interengage. When the jaw assembly 18 and the connected chuck adjusting nut 42 are rotated in the direction indicated, for example, when hand-tightening the chuck on a tool bit "T", the profile of the teeth 114 and 108 permit relative rotation to allow the jaws 32 to tighten on the tool bit "T". Conversely, the tooth profile prevents any counter rotation which would tend to loosen the grip on the tool bit "T". Additionally, the tooth profile configuration allows the chuck to self-tighten in response to torque transmitted through the chuck 10 from the drive spindle 26 to the tool bit "T". More specifically, as the tool bit "T" engages a work piece, a reaction torque is developed that tends to rotate the jaw assembly 18 about the main spindle 24 to advance the jaws 32 and cause them to tighten their grip on the tool bit "T". As this relative rotation takes place, the teeth 114 and 108 increment relative to one another to new relative positions. Since the tooth profile of Figure 22 prevents reverse rotation of the jaw assembly 18 relative to the chuck adjusting sleeve 20, there is no tendency for the keyless chuck 10 to loosen, even if the direction of the drive spindle 26 is reversed. In order to release the tool bit "T", the control sleeve 22 is manually grasped and pulled rearwardly against the resilient urging force of the spring 116 to fully disengage the lock plate 104 from the end of the chuck adjusting nut 42. When the lock plate 104 and the chuck adjusting nut 42 are disengaged, the jaw assembly 18 can be counter rotated relative to the chuck adjusting sleeve 20 to cause the jaw assembly 18 to advance forwardly relative the main spindle 24 and retract the jaws 32 to thus loosen the grip on the tool bit "T". The tooth profile of Figure 22 is well-suited for use in consumer-type power tools where the ultimate torque provided by the tool is sufficient to allow the keyless chuck 10 to fully self-tighten without danger of over-tightening or lock-up. In the case of industrial power tools, however, the ultimate torque provided by the tool can be sufficient to allow the keyless chuck 10 to over-tighten and distort components within the chuck or cause the jaws 32 to crush the surface of the tool bit "T". Figure 23 illustrates a second tooth profile suitable for use on industrial grade tools where it is desirable to 'lock' the keyless chuck 10 from rotation in either direction. As shown, the teeth 114' and 108' have identical steeply inclined flanks 126 and 128 and a flat crest 130. When the teeth 114' and 108' are interengaged, any torque transmitted through the keyless chuck 10 will be insufficient to allow the teeth 114' and 108' to increment relative to one another to allow self-tightening in the forward direction or, conversely, loosening in the reverse direction. Where the tooth profile of Figure 23 is used, the keyless chuck 10 is hand-tightened by first pulling the control sleeve 22 rearwardly to disengage the lock plate 104 from the chuck adjusting nut 42 and is maintained in that position while rotating the jaw assembly 18 relative to the chuck adjusting sleeve 20 until the jaws 32 tighten on the tool bit "T". After hand-tightening is accomplished, the control sleeve 22 is released to allow the spring 116 to urge the lock plate 104 forwardly to engage the teeth 108' and 114'. In this situation, the angle of the guideway 40 of the jaw housing 28 relative to the axis A x is chosen so that hand-tightening of the keyless chuck 10 applies sufficient gripping force to prevent the tool bit "T" from slipping relative to the jaws 32 when the tool's full torque capacity is utilized in either the forward or reverse direction. The tooth pattern of Figure 23 thus prevents self-tightening when applying torque in the forward direction or loosening when operating in the reverse direction. A third tooth profile is shown in Figure 24 and functions to allow the keyless chuck 10 a measure of incremental self-tightening before self-locking. As shown in Figure 24, the lock plate 104 is provided with teeth 114'' having a relatively steep flank 132, another flank defined by surfaces 134 and 136, and a flat crest 138. The chuck adjusting nut 42 is configured with a profile complementary to that of the teeth 114'' to define a series of recurring indentations I1 and I2 with the indentation I1 having a first depth d1 and the indentation I2 having a second depth d2. As shown, the indentation I1 includes an inclined surface 140 designed to engage the surface 136, and the indentation I2 includes the surface 140 for engaging the surface 136 of the tooth 114'' and another surface 144 for engaging the surface 134 of the tooth 114''. When the control sleeve 22 is released after hand-tightening of the keyless chuck 10, the tooth 114'' will advance into indentation I1 so that the surface 136 will engage the surface 140. In this configuration, any additional torque transmitted through the chuck 10 in response to the application of the tool bit "T" to the work piece will cause the chuck adjusting nut 42 to rotate to the right in Figure 24, as indicated by the arrow, effecting a proportional self-tightening of the keyless chuck 10 and causing the tooth 114'' to 'ride' upwardly on the surface 140 of indentation I1 and move along the surface 142 between the indentations to indentation I2 where the tooth 114'' will enter indentation I2 with the surface 136 engaging the surface 140 and the surface 134 engaging the surface 144. Since the indentation I2 has a greater depth dimension d2, a further increase in the torque transmitted through the keyless chuck 10 will be ineffective to cause further incrementing and self-tightening. As can be appreciated, the tooth profile of Figure 24 allows for hand-tightening of the chuck on the tool bit "T" and a limited amount of self-tightening of an under-tightened chuck in response to torque transmitted through the keyless chuck 10. In the embodiment described above, the control sleeve 22 is normally urged in the forward direction with the spring 116 pushing the lock plate 104 into engagement with the chuck adjusting nut 42. In order to temporarily disengage the lock plate 104 from the chuck adjusting nut 42, the operator pulls the control sleeve 22 rearwardly against the force of the spring 116. A second embodiment of a control sleeve 22' and modified lock plate 104' are illustrated in Figures 25 - 30. As shown in FIGURES 25-27, the control sleeve 22' is similar in overall configuration to the control sleeve 22 of Figure 21 and includes an axially extending tubular section 118, a radially enlarged portion 120 at its forward end, and a lock plate camming surface 150 at its rearward end. As shown in Figure 27, the camming surface 150 includes a series of spaced apart axially extending tabs 152 with a first cam 154 and a second cam 156 located between each set of tabs 152. As shown, each of the cams 154 and 156 has respective rising cam surfaces and a flat dwell surface with the cam 154 having a relatively higher dwell surface than the cam 156. The lock plate 104' is similar in structure as that shown in Figures 18 - 20 and includes a ring-like portion 110 having three radially extending tabs 112 and a series of radially aligned teeth 114 on one side surface. As shown in Figure 29, the lock plate 104' also includes three equi-spaced cam formations 160 radially outward of the teeth 114. As shown in Figure 29, the cam formations 160 each include oppositely inclined cam surfaces 162 and 164 and an intermediate surface 166. The control sleeve 22' and lock plate 104' are assembled with the other components of the keyless chuck 10 in the manner described above so that the axially extending tabs 152 of the control sleeve 22' lie on opposite sides of the cam formation 160 of the lock plate 104', as shown in Figure 30. The control sleeve 22' is thus rotatable about the chuck adjusting nut 42 between a first position, shown in Figure 30, in which the cam formation 160 of the lock plate 104' engages the cam 154 of the control sleeve 22', and a second position (not shown) in which the cam formation 160 engages the cam 156. When the control sleeve 22' is in the first position, the larger height D1 of the cam 154 is effective to disengage the lock plate 104' of the chuck adjusting nut 42 and thus disable the locking effect of the teeth on the lock plate 104' and the chuck adjusting nut 42. Conversely, when the control sleeve 22' is rotated to the second position in which the cam formation engages the cam 156, the relatively smaller height D2 allows the teeth 114 on the lock plate 104' to engage the cam adjusting nut 42 to enable the locking mechanism for operation. As can be appreciated, the control sleeve 22' and lock plate 104' of FIGURES 28 to 30 allow disengagement of the locking mechanism by either pulling the control sleeve 22' rearwardly in the manner described above or by disabling or enabling the locking mechanism in response to rotation of the control sleeve 22' in one direction or the other. The major components of the keyless chuck 10 are assembled using a method by which the as-manufactured chuck has a very low run-out and which also allows the chuck to be repeatedly disassembled, serviced, and reassembled without deterioration of the as-manufactured run-out. As shown in Figure 31, the chuck adjusting nut 42 and the jaw assembly 18 are mounted on respective precision mandrels 200 and 202 that are in precise alignment with one another along the principal chuck axis A x . The mandrels 200 and 202 are preferably of the expanding type and locate on axial bore surfaces of the respective components. For example, the mandrel 200 locates on the threaded bore 46 of the chuck adjusting nut 42, and the mandrel 202 locates on the interior bore 38 of the jaw assembly 18. When mounted on their respective mandrels 200 and 202, the chuck adjusting nut 42 and the jaw assembly 18 are thus in optimum axial alignment. As described above in connection with Figure 3, the jaw assembly 18 is assembled, in part, from the jaw housing 28 and the jaw guide 30. While the chuck adjusting nut 42 and the jaw housing 28 are preferably manufactured using powdered metal techniques to provide precision surfaces and the jaw guide 30 is manufactured from a precision die-cast metal, such as aluminum, the accumulated tolerances of the components may be such that the mating surfaces of the chuck adjusting nut 42 and the jaw assembly 18 components, that is, the forward face 206 (Figure 17A) of the chuck adjusting nut 42 and rearward face 204 of the jaw assembly 18 may be less than transverse to the principal axis A x and, accordingly, can contribute to the as-manufactured run-out of the chuck. In order to minimize run-out during the initial assembly of the chuck during manufacture, one of the two mating surfaces, such as the rearward surface 204 of the jaw assembly 18 is defined by a deformable material. The jaw guide 30 (Figure 3) is preferably fabricated from aluminum or zinc magnesium and presents the surface 204, as shown in Figure 31. In the alternative, a separate spacer disc or washer (not shown) having the desired characteristics can be provided. As shown in Figures 31 and 32, the surface 204 is provided with numerous pyramidal structures 208 extending upwardly from the surface 204. The structures are preferably formed as 4-sided pyramids having a height 'h' of between 0.005 and 0.015 inches and an included angle of 90. The pyramids 208 are formed in a rectangular array although other patterns are suitable. The pyramids 208 are designed to present a deformable or crushable surface to the forwardly facing surface 206 of the chuck adjusting nut 42 and are preferably formed in during the die-casting of the jaw guide 30. During the assembly of the keyless chuck 10, the chuck adjusting nut 42 is mounted on its mandrel 200 and the jaw assembly 18 is mounted on its mandrel 202. As indicated above, the mandrels 200 and 202 are precisely located on the principal axis A x of the chuck and thus co-align the chuck adjusting nut 42 and the jaw assembly 18 and position the surfaces 204 and 206 in a confronting relationship. While the rearwardly facing surface 204 of the jaw assembly 18 and the mating, forwardly facing surface 208 of the chuck adjusting nut 42 are nominally transverse to the principal axis A x , manufacturing tolerances are such that these two surfaces may vary from their ideal transverse relationship. In this situation, were the two surfaces secured to together, the major axis of the chuck adjusting nut 42 would be skewed somewhat relative to that of the jaw assembly 18. Any tool bit "T" gripped by the jaw assembly 18 would then wobble about the principal A x . The chuck adjusting nut 42 and the jaw assembly 18 are forced together, for example, under hydraulic pressure, while positionally constrained by the mandrels 200 and 202 to insure precise co-alignment of their respective major axes with the principal axis A x . Where the surface 204 of the jaw assembly 18 and the surface 206 of the chuck adjusting nut 42 are not transverse to the principal axis A x , that is, the surfaces 204 and 206 are non-parallel, the forcible engagement of the two surfaces 204 and 206 will cause selective crushing of the pyramid structures 208. More specifically and depending upon the initial non-transverse alignment of the surfaces 204 and 206, some of the pyramid structures 208 will be substantially crushed while others will be minimally crushed. As a result, an interface is created which is unique to each chuck adjusting nut 42 and jaw assembly 18 to accommodate their unique dimensional characteristics while precisely aligning the chuck adjusting nut 42 and its jaw assembly 18 along the principal axis A x . To retain the unique interface of surfaces 204, 206 producing precise alignment, annular rims 106B (Figure 17B) penetrate into surface 204 and prevent any relative rotation between surfaces 204, 206 during use of the chuck. Any relative rotation would cause a variation in the precise axial alignment of the parts which is achieved during initial assemble. As explained above in relationship to Figure 16, the bores 106 that accept the threaded fasteners 44 that retain the chuck adjusting nut 42 and the jaw assembly 18 together are asymmetrically aligned so that the chuck adjusting nut 42 and the jaw assembly 18 can be assembled in one and only one relative angular relationship. Also, rims 106B will readily reseat in the mating deformations in surface 204 so that precise alignment is again achieved. Thus, when the chuck adjusting nut 42 and the jaw assembly 18 are assembled in the manner described above, the resultant keyless chuck 10 has minimal run-out and can also be repeatedly disassembled and cleaned or otherwise serviced and re-assembled without loss or degradation of the original, as-manufactured run-out. While pyramid structures 208 have been shown in the preferred embodiment, other surface configurations that provide the intended function are suitable, including various types of 'waffle' patterns. In general, the deformable structure of elements must have sufficient height 'h' to accommodate the expected range of misalignment of the surfaces 204 and 206 and be sufficiently spaced from one another to allow the deformed material to flow laterally. As shown in Figures 34-43, the second and preferred embodiment incorporates five basic improvements to the structure and operation of a chuck in accordance with the first embodiment, namely, (1) forwardly spring biased jaws for gripping a bit inserted in the chuck, (2) a lock assembly for preventing excessive tightening or loosening of the jaws on a bit mounted in the chuck, (3) an automatic tightener for tightening a bit in the jaws when use is initiated, (4) a deformable interface between the spindle and the stop for aiding in the alignment of the chuck components during assembly, and (5) a spindle/nut design for more accurate alignment. As shown in Figures 34-43, chuck 301 comprises a jaw assembly 303, a threaded spindle 305, a rear sleeve 307 press fitted on spindle 305 and a lock assembly 309 intermediate rear sleeve 307 and jaw assembly 303. Jaw assembly 303 includes a jaw housing 311 having a forwardly disposed opening 313 for receiving a bit 315, a central guideway 317, a plurality of jaw guideways 319, 321, 323 and a longitudinal axis A x . Spring Biased Jaws In accordance with one feature of the invention, a plurality of spring biased jaws 325, 327, 329 are slidably mounted in the respective jaw guideways 319, 321, 323 between a rearward opened position (Figure 35) and a forward closed position (Figure 34). The jaw guideways 319, 321, 323 are also partially formed by a divider 331 fitted into the rear end of jaw housing 311. Divider 331 (Figures 36, 38B, 38C, 38D) has three upstanding walls 333, 335, 337 which serve to space and guide movement of jaws 325, 327, 329 and has three spaced recesses 339, 341 and 343 to receive the base of a respective jaw 325, 327, 329. In Figures 34, 35; portions of divider 331 are omitted for clarity. A stop 345 (Figures 34, 36B) is engaged with jaws 325, 327, 329 and is slidably mounted in central guideway 317 for maintaining each jaw in the same relative axial location. Guideway 317 (Figure 36B) is defined by internal arcuate guide surfaces 342 in jaw housing 311. Arcuate surfaces 340 on walls 333, 335, 337 are spaced slightly from guideway 317 and do not contact stop 345 during fore and aft movement in guideway 317. Stop 345 (FIGS. 34, 36B, 39A, 39B) includes a cylindrical hub 344 guided by surfaces 342 and three radially extending spokes 347, 349, 351 guided by sides 346 of walls 333, 335, 337. Spokes 347, 349, 351 are received respectively within a slot 352 formed in the base of each jaw 325, 327, 329. As shown by comparing FIGS. 34, 35, forward movement of jaws 325, 327, 329 move each jaw toward longitudinal axis A x and increases the penetration of each lobe 347, 349, 351 respectively within slots 352. Jaws 325, 327, 329 are forwardly biased into a closed position by a biasing means 353. Biasing means 353 is preferably a coil spring. A nut 355 (Figures 34, 35, 40) is fixed to housing 311 and has a threaded opening 357 coaxial of the longitudinal axis A x . Nut 355 is preferably fixed to housing 311 by plurality of bolts 359 (only one shown) captured in openings 360, 361, 362. Alternatively, nut 355 may be fixed to housing 311 by being formed integrally therewith. As shown in Figures 38A, 40C opening 361 has a flaired shape to uniquely mate with a projection 364 on divider 331. On the forward nut face (Figure 40) each opening 360, 361, 362 is surrounded by an annular rim 368 (corresponding to rim 106B (Figure 17B) of the first embodiment) which, upon assembly, penetrates into rear surface 366 of divider 331. As a result, nut 355 and divider 331 can be assembled and reassembled in only one relative angular relationship for the same purpose as described in connection with the first embodiment (FIGS. 1-33). To provide a deformable interface with nut 355, the rear surface 366 of divider 331 has numerous pyramidal structures (not shown) identical to pyramidal structures 208 shown and described in connection with FIGS. 31, 32. Spindle 305 is threadably engaged in nut opening 357; is movable forwardly toward stop 345 to engage and fix stop 345 and jaws 323, 325, 327 in an axial location and to apply clamping force to the jaws; and is movable rearwardly away from stop 345 to remove the clamping force. Forward and rearward movement of spindle 305 is controlled by relative rotation of jaw assembly 303 (jaw housing 311, divider 331 and nut 355) relative to spindle 305 which is fixed to and rotatable with rear sleeve 307 and lock assembly 309. In the preferred embodiment depicted, spindle 305 also forms the output shaft of the power tool. Spindle 305 is supported in the power tool by a bearing 356 and is driven through a gear (not shown) press fitted on the section 358 of spindle 305. Alternatively, spindle 305 may have a threaded open end for retrofitting onto a tool spindle similar to spindle 24 of the first embodiment. In operation, bit 315 is inserted into chuck 301 by inserting the base of the bit axially through opening 313 into central guideway 317. The base of bit 315 pushes the jaws 325, 327, 329 rearwardly against the bias of spring 353 thereby separating the jaws to a diameter sufficient to receive the diameter of bit 315. Bit 315 is preferably inserted into guideway 317 until bit 315 engages the forward face of stop 345. Spring 353 forwardly biases the jaws into engagement with the bit to hold the bit coaxially in guideway 317 for clamping. Bit 315 may then be clamped in guideway 317 by disengaging lock assembly 309 and rotating jaw assembly 303 (jaw housing 311, divider 331 and nut 361) relative to spindle 305, sleeve 307 and lock assembly 309 which are fixed together. Preferably one hand is used to grip and disengage lock assembly 309 and the other hand is used to grip and rotate jaw housing 311 relative to lock assembly 309. Because bit 315 is held in a coaxially centered position, there is no need to grip bit 315 as the clamping force is being applied. In this manner, spindle 305 is advanced into central guideway 317 until the tip of spindle 305 is firmly engaged with the rear face of stop 345 to apply a clamping force to the stop 345 and in turn to jaws 325, 327, 329. When the jaws have been manually tightened on bit 315 in this manner, jaw assembly 303 and spindle 305 are rotatable together. As will be appreciated, the use of spring bias jaws simplifies the mounting of a bit 315 in chuck 301 because there is no need to grip bit 315 following insertion into opening 313. The self holding feature of spring biased jaws is also advantageous if an operator wishes to tighten chuck 301 by rotation of spindle 305 under power. In this instance one hand is used to actuate the drill trigger and the other hand is used to grip lock assembly 309 and jaw housing 311 together. Lock Assembly In accordance with another feature of the invention and as shown in FIGS. 34, 35, 37, 40, 42; lock assembly 309 is movable between a locked position to limit rotation of the spindle 305 relative to the nut 355 and an unlocked position to permit rotation of spindle 305 relative to nut 355. Lock assembly 309 comprises an outer sleeve 363 and an inner sleeve 365 which coaxially surround spindle 305 and nut 355 and are longitudinally slidably between a forwardly biased locked position and a rearward unlocked position. Sleeves 363, 365 are fixed together and are forwardly biased by a coil spring 367 extending coaxially of spindle 305 between an end wall 369 of rear sleeve 307 and an end wall 371 of sleeve 365. Rear sleeve 307 is fixed to spindle 305 with an interference fit on a splined segment 379 (FIGS. 34, 41) of spindle 305 and has a plurality of axially extending guides 381 (Figure 37A). Inner locking sleeve 365 has a plurality of guides 383 interlocking with adjusting sleeve guides 381 for limiting the relative rotation of locking sleeves 365 relative to rear sleeve 307 and for permitting fore and aft movement of sleeve 365 relative to sleeve 307. As shown in Figure 37A, guides 383, 381 are preferably constituted by a plurality of tabs projecting from and extending axially in the outer wall of sleeve 365 interlocking respectively with a plurality of slots extending axially along the inner wall of adjusting sleeve 307. Sleeve 365 is telescopically slidable fore and aft within sleeve 307 and is forwardly biased to engage a plurality of forwardly extending teeth 373 on end wall 371 with a complimentary set of rearwardly extending teeth 375 on rear wall 377 of nut 355 in the locked position and is manually retractable against the bias of spring 367 to disengage teeth 373, 375 in the unlocked position. As shown in Figures 40B, 40D, 42C, teeth sets 373, 375 are sized and spaced to permit a first limited maximum amount of relative rotation between nut 355 and sleeve 365 in a first direction to forwardly advance spindle 305 and a second limited maximum amount of relative rotation between nut 355 and sleeve 365 in a second direction to retract spindle 305. The first amount is larger than the second amount. As shown in Figure 42C, teeth 371 are preferably spaced and centered at 40 increments. As shown in FIGS. 40B, 40D, teeth 373 are preferably spaced and centered at 20 increments providing incremental self-tightening ranging between 0 and 20 and incremental self loosening between 0 and approximately 12. Each tooth 375 (Figure 40D) has a stair stepped profile in the axial direction with a top step 385 and a bottom step 387. A tooth 373 is slidable from the crest of a top step 385 to valley 389 adjacent bottom step 387 and is engagable with the flank 391 of the next adjacent tooth 385 when nut 355 and spindle 305 are relatively rotated to advance spindle 305 and is engagable with the flank 395 of the adjacent bottom step 387 when nut 355 and spindle 305 are relatively rotated to retract spindle 305. In operation, incremental self-tightening occurs when the bit 315 is forwardly driven and is caused by the torque transmitted through the chuck in response to the application of bit 315 to a workpiece causing nut 355 to rotate to the right in Figure 40D as indicated by arrow 392. The incremental self-tightening can range between 0 and 20. A moderate amount of self-tightening is desirable to insure bit 315 is tightly held by the chuck in high torque power tool applications. Following manual tightening by relative rotation of jaw assembly 303 and spindle/sleeve assembly 305, 307, a tooth 373 may initially engage a tooth 375 on any one of the adjacent surfaces 385, 387, 389. When nut 355 is rotated to right as bit 315 is driven in the forward direction, nut 355 may be rotated until a tooth 373 engages a flank 391 of a tooth 375 by sliding tooth 373 across surfaces 385, 387, 389 which are descending in height. Incremental self loosening occurs when a bit 315 is driven in reverse and is caused by the torque transmitted through the chuck from the workpiece causing nut 355 to move to the left in Figure 40D as indicated by arrow 393. Loosening of nut 355 is limited by the movement of a tooth 373 between engagement with flank 391 and opposed flank 395. The limitation of self loosening to less than the full 20 between adjacent top steps 385 of teeth 375 is desirable to prevent a bit from becoming too loose within jaws 325, 327 and 329 of the chuck. Incremental self-tightening is desirable to insure that the bit 315 is adequately tightened for forward drilling. The wide spacing of teeth 375 is desirable to insure that teeth 373 reliably seat and lock within teeth 375 but permits incremental self loosening when driving the bit in reverse direction which is undesirable. The foregoing tooth design limits the amount of loosening to acceptable amounts while permitting a larger level of self-tightening. The preferred amounts of self-tightening and self loosening have been empirically determined. An excessive amount of self-tightening will ultimately prohibit an operator from manually loosening the chuck for bit removable. Incremental self loosening is tolerated to enhance the reliability of the seating and locking of the teeth 373, 375. Automatic Tightener In accordance with another feature of the invention, the chuck comprises an automatic tightener 397 to further increase self-tightening of the jaws 325, 327, 329 on a bit 315 beyond the amount inherent in the design of teeth 373, 375. As shown best in FIGS. 34, 37, tightener 397 is engaged among spindle 305, inner sleeve 365 and nut 355 for tightening jaws 325, 327, 329 on a bit 315 a predetermined amount when (1) spindle 305 is driven, (2) bit 315 is engaged with a workpiece and (3) sleeve 365 is in the locked position. In the preferred embodiment illustrated in FIGS. 37A, 37B, 37C, automatic tightener 397 comprises interlocking slots 381 and tabs 383 which limit the relative rotation of adjusting sleeve 307 and inner sleeve 365. Each slot 381 has an arcuate width extending transverse to the longitudinal axis A x greater than the arcuate width of tab 383 to permit a predetermined amount of relative rotation between rear sleeve 307 and inner sleeve 365. Sleeve 365 is thus rotatable relative to rear sleeve 307 within the limits of movement permitted by the movement of tabs 383 within slots 381. When a bit 315 is tightened manually, teeth 373, 375 are disengaged and tabs 383 are moved counterclockwise in slots 381 as shown in Figure 37B. Then when locking assembly 309 is locked and bit 315 is engaged with a workpiece, tabs 383 are then shifted clockwise in slot 381 to incrementally self tighten a predetermined amount. The range of movement of tabs 383 within slots 381 determines the amount of self-tightening provided by the automatic tightener in addition to the 0 - 20 self-tightening provided by teeth 373, 375. To operate the automatic tightener, lock assembly 309 is disengaged by sliding sleeve 365 rearwardly against the bias of spring 367 to disengage sleeve teeth 373 and nut teeth 375. Then jaw assembly 303 is manually rotated clockwise while rear sleeve 307 is held initially stationary (as viewed by facing the front of the chuck) (Figure 37A). When jaws 325, 327, 329 are tightened on a bit 315, jaw assembly 303 and the spindle/sleeve assembly 305, 307 are rotated as a unit clockwise (Figure 37A) while sleeve 365 is held in the retracted position. By holding sleeve 365 in a retracted position, tabs 383 are shifted in slots 381 until the leading edge of slot 381 engages the trailing edge of tab 65 as shown in Fig 37B. When tightening of the bit is complete, sleeve 365 is released and is spring biased into a locked position with teeth 373, 375 engaged. Upon initial drilling with bit 315 in a workpiece, a counterclockwise torque is applied to jaw assembly 303 through teeth 373, 375 to sleeve 365. As shown in Figure 37C, sleeve 365 is automatically rotated clockwise relative to spindle 305 and rear sleeve 307 to shift the leading edges of tabs 383 into engagement with the trailing edges of slots 381. This results in the advancement of spindle 305 toward stop 345 and increased tightening of jaws 325, 327, 329 on a drill bit 315. Spindle/Stop Deformable Interface In accordance with another feature of the invention, the chuck further comprises, as shown in Figure 43, a deformable interface 401 between stop 345 and spindle 305 for facilitating the coaxial alignment of spindle 305 and stop 345. Deformable interface 401 comprises the interface between the front face 403 of spindle tip 405 and a centrally disposed projection 407 on stop 345 and the interface between an edge 409 on spindle tip 405 and the inner wall 411 of a rim 413 formed on stop 345 surrounding projection 407. Rim wall 411 and tip side wall 412 are inclined at outwardly divergent angles so that contact between tip 405 and rim 413 is limited to a narrow annular band surrounding edge 409. For example, in the preferred embodiment, the angle 0₁ between wall 411 and the horizontal is 30 and the angle 0₂ between wall 412 and the horizontal is 29. Alternatively, rim wall 411 and tip side wall 412 may be inclined (from the interface between walls 411, 412) at inwardly divergent angles. Projection 407 is sized to form a small area patch following deformation in accordance with the criteria set forth for patch 72 (Figure 8) of the first embodiment). In the preferred embodiment, the distal end of tip 405 is frustroconical such that face 403 and surrounding edge 409 are circular and rim 413 formed on stop 345 is annular. It will be recognized that a wide range of complimentary shapes are suitable consistent with the objectives of limiting the contact area between spindle 305 and stop 345 and the deformability of the interface 401 when spindle 305 is forced into engagement with stop 345 upon assembly of the chuck. Spindle 305 is made of steel and stop 345 is made of precision blanked steel. When the chuck is first assembled, jaw assembly 303 and nut 355 are held in precise coaxial alignment and the rear assembly of rear sleeve 307 and spindle 305 are held in precise coaxial alignment. Thus as spindle 305 is screwed into engagement with stop 345, tip 405 and stop 345 are precisely seated relative to each other consistent with the coaxial alignment of their assemblies. The interface between edge 409 and rim sidewall 411 is deformed by edge 409 cutting into and forming a circular recess in sidewall 411. The interface between projection 407 and spindle tip face 403 is deformed by the formation of a flattened surface on projection 407 which functions as a small area contact patch as in the first embodiment. In subsequent use of chuck 11, stop 345 retains jaw housing in precise alignment with spindle 305 because of (1) the precision fit of stop 345 within central guideway 317 and (2) the precision formed interface 401 between spindle 305 and stop 345. Spindle/nut Alignment In accordance with another feature of the invention and as shown best in FIGS. 34, 40A, 41, spindle 305 has a precision ground cylindrical first section 415 mating with a precision formed smooth walled the first section 417 of nut opening 357 and has a threaded second section 421 mating with a threaded second section 423 of nut opening 419. Spindle threaded section 421 has a flattened outer surface equal in diameter to the spindle smooth section 415. Spindle section 421 is formed by first threading and then grinding to a precise outer diameter which flattens the sharp points of the threads. The interface between spindle smooth section 415 and nut smooth section 417 determines the precise coaxial alignment of nut 355 and spindle 305. The threads of threaded spindle section 421 and threaded nut section 423 are formed to have only a loose meshing engagement to control fore and aft movement of the spindle through the nut without affecting the coaxial alignment. The mating cylindrical interfaces of the nut and spindle enable greater precision in the coaxial alignment compared with a mating interface relying in part on threading accuracy for alignment. A removable retainer 425 is press fitted on spindle tip 405 projecting through the forward end of nut 355 for preventing removal of the spindle 305 from nut 355 in normal operation and for permitting selective removal of spindle 305 from nut 355 for servicing of chuck 301. Spindle tip 405 has a diameter smaller than the diameter of nut opening 357 and has a slightly enlarged rim 431 to form a tight frictional fit with the inner diameter of retainer 425. Retainer 425 is preferably a conical washer having an outer diameter larger than the diameter of nut opening 357 and slightly smaller than the inner diameter of divider opening 429 and having a forwardly facing convex face 427. When spindle 305 is retracted the maximum amount to position washer 425 in divider opening 429 with the rear face of washer 425 in engagement with the forward face of nut 355, divider opening 429 restrains the flattening of washer 425 to prevent removal of spindle 305 from nut 355 in normal operation. For removal, a high torque load is applied manually to chuck 301 for relative rotation of nut 355 and spindle 305 to force the sliding of tip 405 from retainer 425. The present invention advantageously provides numerous features which may be used individually or in combination. The keyless chuck may have a relatively low internal operating friction because of the small-area contact between the main spindle and the jaw thrust member (or stop) and because the spindle has a small outer diameter relative to the outer diameter of the chuck. The locking mechanism may provide for uni-directional or by-directional locking of the chuck adjusting sleeve relative to the jaw housing, selective disablement of the locking mechanism, reliable seating for locking and/or incremental self-tightening. The mounting of the bit in the chuck may be simplified by the forwardly spring biased (self-centering) jaws for gripping a bit inserted into the chuck. The chuck may be initially assembled with one or more deformable surfaces which accommodate any accumulated manufacturing tolerances to provide a finished chuck with minimal run out. Also, to further enhance the accuracy of assembly and reduce run out, the spindle and nut may be provided with a smooth walled interface to accurately control coaxial alignment of the nut and spindle. Thus it will be appreciated from the above that as a result of the present invention, a highly effective keyless chuck and method of assembly therefor is provided by which the principal objective, among others, is completely fulfilled.

Claims: A chuck comprising: a jaw housing (28; 311) having a forwardly disposed opening (313) to receive a bit (T; 315), a central guideway (38; 317), a plurality of jaw guideways (40; 319, 321, 323) and a longitudinal axis (A x ); a plurality of jaws (32; 325, 327, 329) slidably mounted in the jaw guideways between a rearward opened and a forward closed position; a carrier (345) engaged with the jaws and slidably mounted in the central guideway for maintaining each jaw in the same relative axial location; a nut (42, 355) fixed to the jaw housing and having a threaded opening (46; 357) coaxial of the longitudinal axis; a threaded spindle (48; 305) engaged in the nut opening and movable forwardly to apply clamping force to the jaws and rearwardly to remove clamping force; a manually actuated locking member (22, 104, 42; 309) movable between (a) a locked position engaging the nut to limit the relative rotation of the spindle and nut and (b) an unlocked position disengaging the nut to permit relative rotation of the spindle and nut; a rear sleeve (307) fixed to the spindle; said nut and locking member having teeth (373, 375) engaged in the locked position and disengaged in the unlocked position; characterized in that: said rear sleeve and locking member have an engaged tab (383) and slot (381) to limit the relative rotation of the rear sleeve and locking member, said slot having a width extending transverse to the longitudinal axis greater than the transverse width of the tab to permit a predetermined amount of relative rotation between the rear sleeve and locking member; and said tab and slot comprise an automatic tightener for tightening the jaws on a bit a predetermined amount when the spindle is driven, the bit is engaged with a workpiece and the locking member is in the locked position. A chuck according to claim 1, wherein said slot extends axially along the inner wall of the rear sleeve, said locking member (309) includes a sleeve (365) and is telescopically adjustable relative to the rear sleeve (307), and said tab (383) projects from an outer wall of the locking sleeve. A chuck according to claim 1, wherein said nut has a first set of spaced teeth (375), said locking member (309) and a second set of spaced teeth (373) and the size and spacing of the two sets of teeth permitting a first limited maximum amount of relative rotation between the nut and locking member in a direction to advance the spindle. A chuck according to claim 3, wherein the size and spacing of the two sets of teeth (373, 375) permits a second limited maximum amount of relative rotation between the nut (355) and locking member (309) in a second direction to retract the spindle (305) and the first amount being larger than the second amount. A chuck according to claim 1, wherein each tooth (375) of one set of teeth (375) has a stair stepped profile in the axial direction and with the top and bottom steps (385, 387), the teeth of the second set slidable from the crest of the top step to the valley (389) adjacent the bottom step and engageable with the flank (391) of the next adjacent tooth (385) of the first set of teeth when the nut and spindle are relatively rotated to advance the spindle and engageable with the flank (395) at the bottom step (387) when the nut and spindle are relatively rotated to retract said spindle. A chuck according to claim 1, characterized by biasing means (353) for resiliently biasing the jaws to a closed position. A chuck according to claim 1, wherein relative rotation of the jaw housing (28) and the spindle (48) in a first direction applies a force to forwardly advance the jaws (32) and relative rotation in the opposite direction applies a force to rearwardly retract the jaws (32). A chuck according to claim 1, characterized by: a divider (30; 331) in the jaw housing for spacing and guiding movement of the jaws, said divider having a plurality of axially extending walls (333, 335, 337), each wall having a guide surface (346); said jaw housing having a plurality of axially extending guide surfaces (342) adjacent, respectively, one of the divider guide surfaces (346); the central guideway (38; 317) defined by the divider guide surfaces and the jaw housing guide surfaces; and said carrier (34; 345) having a hub (62; 344) engaging and guided by the central guideway and a plurality of spokes (64; 347, 349, 351) extending transversely from the hub engaging respective ones of the jaws.

Inventors: COLEMAN CHARLES W, WHEELER DALE K, COLEMAN, CHARLES W., WHEELER, DALE K.
Applicants: BLACK & DECKER INC, BLACK & DECKER INC.
Application year: 1991
Main classification: B23B31
IPC codes: B23B31