Tool holding device incorporating a solid film lubricant

An improved tool holding device has at least one tool engaging member for selectively engaging a tool during operation, such as the jaw blades of a chuck device and gripping jaw blades of a collet device. The tool holding device includes an actuating mechanism for causing the tool engaging members to selectively engage upon a tool. The actuating mechanism includes at least two components in frictional engagement. At least a portion of the frictional engaging components is coated with a solid film lubricant.

BACKGROUND OF THE INVENTION 
The present invention relates to an improved tool holding device, and more 
particularly to a tool holding device incorporating a solid film lubricant 
for enhancing the overall gripping strength and efficiency of such tool 
holding devices. 
Tool holding devices are well known in the art for various applications. 
For example, such tool holding devices include chuck devices (both keyed 
and keyless) and collet devices (both split-steel collets and the 
Rubber-Flex.RTM. collet from Jacobs.RTM. Chuck Manufacturing Company). 
Tool holding devices also include fastening devices or mechanisms for 
attaching grinding discs, saw blades, and the like to drive spindles. 
These fastening devices may include conventional nuts, torque enhancing 
nuts, or similar mechanisms. The various applications and operation of 
conventional tool holding devices is well understood by those skilled in 
the art. 
Many of these devices, such as keyed and keyless chucks and collets, work 
on a principle of sliding frictional engagement of actuation members to 
cause engaging members to grip a tool held in the device. The frictional 
interfaces are operationally unavoidable, but are the major contributor of 
wear and eventual degradation of such tool holding devices. The art is 
constantly striving to reduce the effects of friction with such devices so 
as to extend the life of the products. For example, it is known in the art 
to coat various components of such devices with zinc phosphate in an 
attempt to reduce friction between the components. Additionally, the 
components are typically packed with grease or other flowable type of 
lubricants in an attempt to reduce friction. However, although relatively 
effective at reducing friction, grease and oil present their own problems 
in that the grease/oil tends to collect dirt and abrasion particles and 
eventually leads to fouling of the devices. Additionally, grease/oil also 
presents a significant bleed-out problem. 
Conventional lubricants such as oils and greases have also proved fairly 
limiting in higher pressure or increased load applications. Under normal 
loads, the oils and greases provide adequate separation between the 
metallic asperities in the surfaces of the frictionally engaging metallic 
members. However, under heavier loads, boundary lubrication occurs with 
typical oils and greases which results in contact of the asperities in the 
surfaces. The conventional dry lubricants, such as zinc phosphate, present 
a similar problem in that such lubricants are typically extremely thin at 
the contact areas of the asperities in the opposing surfaces and, thus, 
have relatively little lasting capacity over the life of the product. 
Thus, applicants of the present invention set out to provide an improved 
tool holding device having significantly greater frictional wear 
characteristics and increased gripping torque than anything known or 
appreciated in the art. 
OBJECTS AND SUMMARY OF THE INVENTION 
It is therefore a principal object of the present invention to provide an 
improved tool holding device having frictional wear characteristics. 
It is also an object of the present invention to provide a tool holding 
device having improved gripping torque or strength. 
An additional object of the present invention is to provide an improved 
collet tool holding assembly. 
And yet still another object of the present invention is to provide an 
improved chuck device. 
Still another object of the present invention is to provide a method for 
increasing the wear characteristics and gripping torque or strength of any 
manner of tool holding devices. 
Additional objects and advantages of the invention will be set forth in the 
following description, or may obvious from the description, or may be 
learned through practice of the invention. 
Applicants have developed a significantly improved tool holding device 
incorporating a solid film lubricant coating on certain critical elements 
of the device, as well as an improved method of manufacturing a tool 
holding device. Applicants' present invention not only provides a tool 
holding device having improved wear characteristics, but also provides a 
device having significantly improved gripping strength or torque. 
In accordance with the objects and purposes of the invention, an improved 
tool holding device is provided. The tool holding device includes at least 
one tool engaging member for selectively engaging a tool or tool shank 
during operation of the device. The improved tool holding device further 
includes an actuating mechanism for causing at least one of the tool 
engaging members to selectively engage upon the tool. The actuating 
mechanism includes at least two components in sliding frictional 
engagement. At least one portion of one of the components in frictional 
engagement is coated with a solid film lubricant. Preferably, the one 
component coated with the solid film lubricant is completely coated with 
the thickness of the coating being in the range of 0.0001 to 0.0005 inches 
thick. In a preferred embodiment, only one of the frictionally engaged 
components is coated with the solid film lubricant. In an alternative 
embodiment, at least a portion of both of the components are coated. 
In a preferred embodiment of the invention, the tool holding device 
preferably comprises a chuck for use with a manual or powered driver. The 
chuck includes a generally cylindrical body member having a nose section 
and a tail section. The nose section has an axial bore formed therein to 
mate with the drive shaft of a driver and the nose section has an axial 
bore formed therein and a plurality of angularly disposed passageways 
formed therethrough which intersect the axial bore. A plurality of jaws 
are slidably positioned in each angularly disposed passageways. Each of 
the jaws has a jaw face formed on one side thereof and threads formed on 
the opposite side thereof. A nut is rotatably mounted on the body and is 
in engagement with the threads on the jaws. At least one of the nut or the 
threads on the jaws is at least partially coated with a solid film 
lubricant. 
The chuck further includes a generally cylindrical sleeve member in driving 
engagement with the nut whereby the sleeve is rotated with respect to the 
body member. Preferably, only one of the surfaces of the nut or the 
threads on the jaws is coated with the solid film lubricant, and 
preferably coated completely with the lubricant. In an alternative 
embodiment, both of the surfaces may be coated with the lubricant. The 
thickness of the coating on either of the surfaces is in the range of 
approximately 0.0001 to 0.0005 inches. 
In an alternative preferred embodiment of the improved tool holding device, 
a machine tool collet is provided which is actuated by engagement with a 
mating surface of a collet holder. In this embodiment, the tool engaging 
members include the plurality of gripping jaws in the collet, and 
particularly the inner diameter faces of the gripping jaws. The gripping 
jaws are held in a desired longitudinally and equally spaced angular 
position about the longitudinal centerline through the collet with 
resilient material disposed between the gripping jaws. The gripping jaw 
inner faces are parallel to the centerline axis and define an inner 
diameter opening for receipt of a tool shank. The actuating mechanism 
comprises the conical outer surface of the collet defined by the outer 
faces of the gripping jaws and a complimentary conical surface of the 
collet holder which engages the outer faces of the gripping jaws. At least 
one of the collet holder conical surface or the gripping jaw outer faces 
is coated with a solid film lubricant. In a preferred embodiment, only one 
of such a surfaces is coated. Alternatively, both of the surfaces may be 
coated. 
The present invention also includes an improved method of manufacturing a 
tool holding device, such as a chuck or collet device. The method includes 
the steps of providing at least one tool engaging member for selectively 
engaging a tool during operation. For example, in the chuck embodiment, 
the tool engaging member includes the jaws movable in the plurality of 
angularly disposed passageways through the chuck body. In the collet 
embodiment, the engaging members include the plurality of gripping jaws, 
and particularly the inner faces of the gripping jaws. 
The method according to the invention further includes providing an 
actuating mechanism for causing the tool engaging members to selectively 
engage upon the tool. The actuating mechanism includes at least two 
components in frictional engagement. For example, in the chuck embodiment, 
the members in frictional engagement include the threads on the rotatable 
nut and engaging threads defined on the movable jaws. In the collet 
embodiment, the components in frictional engagement include the conical 
outer surface of the collet defined by the outer faces of the gripping 
jaws and the complimentary conical surface of the collet holder. 
The claimed method further includes coating at least one of the components 
which is in frictional engagement with a solid film lubricant. Preferably, 
only one of the components is coated. Alternatively, both of the 
components may be coated. 
The accompanying drawings, which are incorporated in and constitute a part 
of the specification, illustrate embodiments of the invention and, 
together with the description, serve to explain the principles of the 
invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Reference will now be made in detail to the presently preferred embodiments 
of the invention, one or more examples of which are illustrated in the 
accompanying drawings. Each example is provided by way of explanation of 
the invention, and not limitation of the invention. In fact, it will be 
apparent to those skilled in the art that various modifications and 
variations can be made in the present invention without departing from the 
scope or spirit of the invention. For instance, features illustrated or 
described as part of one embodiment, can be used on another embodiment to 
yield a still further embodiment. Thus, it is intended that the present 
invention cover such modifications and variations as come within the scope 
of the appended claims and their equivalents. The numbering of components 
in the drawings is consistent throughout the application, with the same 
components having the same number in each of the drawings. 
The present invention relates to tool holding devices in general. Such 
devices may include keyed chucks, keyless chucks, all types of collets, 
quick release chuck devices, tapping attachment devices, nuts and torque 
enhancing devices for attaching saw blades or grinder discs to drive 
spindles, and any other manner of device or mechanism for attaching a tool 
with a driving member. The present invention will be explained and 
described by way of example through two preferred embodiments of the 
present invention, particularly a keyless chuck, and a collet system. 
However, it should be understood that this is in no means meant to limit 
the scope of the present invention. Any manner of tool holding device 
incorporating the essential features described herein is within the scope 
and spirit of the invention. Thus, any manner of tool holding device 
incorporating components in frictional engagement are included in the 
present invention. 
As will be explained in detail below, the present invention includes the 
use of a solid film lubricant applied preferably as a coating to certain 
key frictional engaging components of the tool holding devices. A brief 
description of solid film lubricants is provided for ease in understanding 
in the present invention. 
Solid film lubricants are also known as "dry film lubricants" or "bonded 
film lubricants." Solid film lubricants consist primarily of binders and 
pigments. Binders perform a carrier or anchoring function to hold the 
solid lubricating pigments in position and allow wear of the pigments 
through the life of the film. Thus, the binder and pigments maintains a 
lubricating matrix of dispersed solid particulate lubricating pigments 
through the entire life of the film. The binders consist primarily of 
resins such as phenols, alkyd, epoxy, and combinations thereof. Inorganic 
binders are also available and usually consist of silicate type materials. 
The curing times and temperatures for the solid film lubricants depend on 
the nature and type of binder utilized. The more successful and stable 
products contain binders that require baking to cure the film. However, 
air dry type of resin binders also exhibit excellent properties, 
especially if force cured at 130.degree. Fahrenheit for twenty to thirty 
minutes. 
The particulate pigments carried in the binders are chiefly of the 
molybdenum disulfide and graphite type. The most common combination is a 
90% molybdenum disulfide in combination with 10% graphite. 
Referring to FIGS. 1 and 4 in general, an improved tool holding device, 
designated generally as A, is depicted. Device A includes at least one 
tool engaging member, generally B, for selectively engaging a tool during 
operation, such as the drill bit 70 illustrated in FIG. 4. Tool holding 
device A also includes an actuating mechanism, generally C. Mechanism C 
causes the tool engaging member B to selectively engage upon the tool. As 
will be discussed in greater detail below in the description of the 
preferred embodiments, actuating mechanism C includes at least two 
components in frictional engagement. At least a portion of one of the 
components in frictional engagement is coated with a solid film lubricant, 
generally 32 in FIGS. 2 and 3. 
Applicants have determined that the solid film lubricants as discussed 
above are preferred in tool holding device applications in that the 
lubricants resist adhesion of lint, dust, and corrosion products. The 
solid film lubricants are extremely adherent and will not bleed out 
internally from the tool holding devices as oil and grease does with 
conventional chucks. 
Applicants have determined that a preferred cured film thickness for the 
components coated with the solid film lubricant is between 0.0001 and 
0.0005 inches. The solid film lubricant coating is preferably applied by 
spraying the lubricant onto the components. Alternatively, the components 
may be dipped or spray tumbled. 
The metallic surfaces of the actuating mechanism C in the present tool 
holding device A contain microscopic peaks and valleys or "asperities." 
The solid film lubricants are applied to the surfaces and cover the 
asperities with a solid film having a definite thickness of preferably 
between 0.0001 and 0.0005 per side coated. The coated surface slides 
either against a mating coated surface, or preferably against an uncoated 
surface. In the embodiment wherein only one of the frictional surfaces is 
coated, a thin film is transferred from the coated surface to the mating 
asperities in the uncoated surface. 
Applicants have found that a preferred solid film lubricant for use with 
tool holding devices as described herein is PERMA-SLIK.RTM. by E/M.RTM. 
Corporation of West Lafayette, Ind. The PERMA-SLIK.RTM. lubricant is 
applied by dipping the components and curing at 130-140 degrees Fahrenheit 
for a period of eight to fifteen minutes. The PERMA-SLIK.RTM. solid film 
lubricant is but one of any number of solid film lubricants which may be 
applicable to the present invention. 
A preferred embodiment of a tool holding device A according to the present 
invention is particularly illustrated in FIGS. 1 and 2. In this preferred 
embodiment, a keyless or hand operated chuck 10 is provided. Chuck 10 
includes a front sleeve member 34, an optional rear sleeve member 35, a 
body member 12, and jaws 24. Body member 12 is generally cylindrical in 
shape and comprises a nose or forward section 14 and a tail or rearward 
section 16. An axial bore 20 is formed in the nose section 14 of the body 
member 12. Axial bore 20 is somewhat larger than the largest tool shank 
that the chuck is designed to accommodate. A threaded bore 18 is formed in 
tail section 16 of body 12 and is of a standard size to mate with the 
drive shaft of a powered or hand driver (not shown). The bores 20, 18 may 
communicate at the central region of the body member 12. While a threaded 
bore 18, is illustrated, such bore could be replaced with a tapered bore 
of a standard size to mate with a tapered drive shaft. Passageways 22 are 
formed in body member 12 to accommodate each jaw 24. Preferably, three 
jaws 24 are employed and each jaw 24 is separated from the adjacent jaw by 
an arc of approximately 120.degree.. The axis of the passageways 22 and 
the jaws 24 are angled with respect to the chuck axis but intersect the 
chuck axis at a common point ahead of the chuck body 12. Each jaw 24 has a 
tool engaging face 26 which is generally parallel to the axis of the chuck 
body 12 and threads 28 on its opposite or outer surface. Threads 28 of any 
suitable type and pitch may be utilized within the scope of the present 
invention as would be readily apparent to one skilled in the art. 
As illustrated in FIGS. 1 and 2, body member 12 may include a thrust ring 
member 36 which, in a preferred embodiment, is integral therewith. Thrust 
ring member 36 includes a plurality of jaw guide ways 37 formed around the 
circumference to permit retraction of the jaws 24 therethrough. Thrust 
ring member 36 may have an arcuate seating surface for receipt of a 
self-contained bearing assembly, as will be described. 
Body member 12 includes a rear cylindrical portion with a knurled surface 
13 formed thereon for receipt of optional rear sleeve 35 to be pressed 
thereon if so desired. 
The present invention further includes a nut 30 which, in a preferred 
embodiment, is a unitary nut and which includes threads 31 for mating with 
threads 28 on jaws 24 whereby when the nut is rotated with respect to the 
body, the jaws will be advanced or retracted. As illustrated in FIG. 2, 
nut 30 includes drive slots 29 for mating with drive ribs 33 on front 
sleeve 34 so that when front sleeve 34 is rotated, nut 30 will rotate 
therewith and move jaws 24 as set forth above. 
A self-contained bearing assembly 38 is adapted to be placed between thrust 
ring 36 and a face of nut 30. Self-contained bearing assembly 38 includes 
an inner race 40, an outer race 42, and bearing elements 41 maintained 
therebetween. In a preferred embodiment, bearing elements 41 are ball 
bearings. Self-contained bearing assembly 38 may further include a shroud 
43 surrounding the inner and outer races for maintaining the bearing 
assembly as a self-contained component. In a preferred embodiment, 
self-contained bearing assembly 38 is a radial thrust bearing. It should 
be appreciated that any type bearing arrangement, including plain bearing 
surfaces, could be utilized in the present invention. 
Referring again to FIGS. 1 and 2, a nut retainer member is generally 
illustrated as 37. Nut retainer member 37 includes a first generally 
cylindrical portion 37b and a second frusto-conical portion 37a. 
Substantially cylindrical portion 37b in configured to be press-fitted 
over nose or forward section 14 in a location so that a portion thereof 
will engage nut 30 to prevent nut 30 from moving axially forward more than 
a desired amount. This desired amount can be determined by the location in 
which the nut retainer member is press-fitted to the body member. It 
should be appreciated that the nut retainer member is adapted to be 
press-fitted onto the nose portion of the body, but could be secured in 
any other suitable manner in accordance with the present invention. 
Front sleeve member 34 is adapted to be loosely fitted over nose section 14 
of chuck 10. Drive ribs 33 of front sleeve 34 engage drive slots 29 of nut 
30 so that front sleeve 34 and nut 30 will be operatively rotational 
connected, i.e., when front sleeve 34 is rotated, nut 30 will rotate 
therewith. 
A nose piece 39 is dimensioned and adapted to be pressed onto the front of 
the forward section 14 of body member 12 to maintain front sleeve 34 on 
chuck 10. It should be appreciated that nose piece 39 could also be 
secured by snap fit, threading, or the like. Nose piece 39 is exposed when 
the chuck is assembled and is preferably coated with a non-ferrous 
metallic coating to prevent rust and to enhance its appearance. In a 
preferred embodiment, such coating may be zinc or nickel, however, it 
should be appreciated that any suitable coating could be utilized. 
Nose piece 39 serves to maintain front sleeve member 34 in position on 
chuck 10 and in driving engagement with nut 30. In addition, nose piece 39 
serves the dual purpose of providing an aesthetically pleasing cover for 
the nose portion that inhibits rust. This provides the advantage of an 
aesthetically pleasing appearance without the necessity to coat the entire 
body member 12 with a non-ferrous material. 
If desired, the rear sleeve member 35 may be omitted and the front sleeve 
member 34 extended to the tail end of body 12. This alternative is 
feasible with a spindle lock or the like is provided on the driver or when 
the driver is used to tighten or loosen the jaws. 
It should be appreciated that a snap ring or any other mechanism could be 
utilized to maintain front sleeve 34 in place in lieu of nose piece 39. 
The circumferential surface of the front sleeve member 34 may be knurled or 
may be provided with longitudinal ribs or other protrusions to enable the 
operator to grip it securely. In like manner, the circumferential surface 
of the rear sleeve member 35, if employed, may be knurled or ribbed if 
desired. The front and rear sleeves may be fabricated from a structural 
plastic such as polycarbonate, a filled polypropelene, for example, glass 
filled polypropelene, or a blend of structural plastic materials. Other 
composite materials such as, for example, graphite filled polymerics would 
also be suitable in certain environments. As will be appreciated by one 
skilled in the art, the materials from which the chuck of the present 
invention is fabricated will depend on the end use of the chuck, and the 
above are provided by of example only. 
It will be further appreciated that rear sleeve member 35 is fixed to body 
member 12 while front sleeve member 34 is operatively associated with nut 
30 and secured to body member 12 for relative rotation therewith. Relative 
movement of the front and rear sleeve members due to the interaction 
between threads 28 on jaws 24 and threads 31 on nut 30 causes jaws 24 to 
be advanced or retracted, depending upon the direction of relative 
movement. 
At least one of the surfaces of the frictional interface between nut 30 and 
jaw threads 28 is coated with a solid film lubricant as described above. 
In the embodiment illustrated, solid film lubricant 32 completely coats 
nut 30. It is preferred that the lubricant coat any part of nut 30 that is 
subject to frictional engagement with other components of the device. 
However, for ease of coating, the entire nut 30 is simply sprayed or 
dipped in solid film lubricant 32. 
In an alternative embodiment not illustrated, solid film lubricant 32 may 
be applied as a coating to jaws 24, and particularly to jaw threads 28. 
Applicant has determined that it is preferred to only coat one of the 
frictional engaging surfaces of nut 30 and jaws 24. For example, it is 
preferred that either nut 30 (at least threads 31) is coated with solid 
film lubricant 32 while jaws 24 remain uncoated. Alternatively, jaws 24 
may be coated while nut 30 remains uncoated. It is also within the scope 
of the invention to coat both frictionally engaging surfaces of nut 30 and 
jaws 24. 
FIGS. 3 and 4 illustrate another preferred embodiment of an improved tool 
holding device A according to the present invention particularly relating 
to a collet and collet holder system. Referring particularly to FIG. 4, a 
collet holder 46 is illustrated. Collet holder 46 includes a body member 
47 having a frusto-conical inner diameter surface 48 defined therein. Body 
member 47 includes a longitudinally extending stem portion 51 which is 
matable to a drive spindle (not shown). In an alternative embodiment, stem 
51 may comprise the drive spindle itself. 
A collet 44 is received within the body 47 of collet holder 46, as commonly 
understood by those skilled in the art. The arbor end of collet holder 46 
includes a threaded outer diameter as illustrated. A nut member 49 is 
provided having a threaded inner diameter for threaded engagement with the 
arbor end of body 47. 
The device illustrated in FIG. 4 operates by placing a collet 44 within the 
frusto-conical recess defined in body member 47 and subsequently screwing 
nut 49 onto the arbor end. As nut 49 is moved axially through threaded 
rotational engagement, it forces collet 44 to compress and grip shaft 66 
of tool 70 held within the inner diameter opening of the collet. Thus, a 
frictional interface exists between the outer diameter frusto-conical 
surface of collet 44 and the inner diameter frusto-conical surface of body 
member 47 of collet holder 46. 
According to the invention, at least one of the frictional interface 
surfaces, frusto-conical surface 48 of body member 47 or frusto-conical 
outer diameter surface 58 of collet 44, is coated with a solid film 
lubricant as described above. It is preferred that only one of the 
surfaces is coated and preferably within the range of 0.0001 and 0.0005 
inches. Alternatively, both such surfaces could be coated. 
FIG. 3 depicts a preferred embodiment of a collet according to the 
invention incorporating a solid film lubricant as discussed above. FIG. 3 
illustrates a type of collet widely recognized in the art as a 
Rubber-Flex.RTM. collet from Jacobs.RTM. Chuck Manufacturing Company. 
Collet 44 includes a plurality of gripping jaws 50 held in a desired spaced 
relation relative to each other and the longitudinal centerline 52 (FIG. 
4) through collet 44. Gripping jaws 50 are held in place by resilient 
material 62 disposed between each gripping jaw. Material 62 also 
preferably extends through perforations 72 defined through gripping jaws 
50 so as to form essentially concentric rings of resilient material 62 
through gripping jaws 50. 
Gripping jaws 50 are disposed around longitudinal centerline 52 such that 
inner faces 54 of jaws 50 define an inner diameter opening 56 for receipt 
of a tool shank 68, as illustrated in FIG. 4. Jaws 50 also include an 
angled exposed outer face 58 whereby the plurality of jaws 50 define an 
essentially frusto-conical shaped outer diameter surface which compliments 
the frusto-conical receiving surface 48 of the body 47 of collet holder 
46. As depicted in FIG. 3, resilient material 62 may be defined generally 
below the exposed outer faces 58 of jaws 50. In an alternative preferred 
embodiment not illustrated, resilient material 62 may be generally flush 
with the outer exposed faces 58 of jaws 50. Compression recesses (not 
shown) may also be defined in resilient material 62 between jaw blades 50 
to allow for greater compression of collet 44 within its respective mating 
collet holder 46. The necessity of compression recesses is dependent upon 
the resiliency and/or volume of resilient material disposed between the 
respective gripping jaws. 
In many applications of collets 44, it is highly desirable to conduct a 
coolant fluid through the collet 44 and collet holder 46. In this regard, 
collet 44 preferably includes a continuous outer diameter seal, as 
illustrated in FIG. 3. Outer seal 64 is formed preferably integral with 
resilient material 62, and preferably is formed of the same material as 
resilient material 62. In this manner, outer diameter seal 64 is molded 
integral with resilient material 62. In a preferred embodiment of the 
invention, outer seal 62 comprises a double-lip seal, as indicated in FIG. 
3. In an alternative embodiment, seal 64 may comprise a single lip. 
Collet 44 also preferably includes a continuous inner diameter seal 66, as 
illustrated in FIG. 4. The inner diameter seal is not illustrated in FIG. 
3 so as to indicate that the inner faces 54 of jaws 50 are not coated with 
solid film lubricant 32. Inner diameter seal 66 is also preferably formed 
integral with resilient material 62 and, preferably, also comprises a 
double-lip seal. Again, this double-lip seal is also preferably molded 
integral with resilient material 62. 
The design and operation of the continuous inner and outer diameter seals 
of the present inventive collet are discussed extensively in U.S. Pat. No. 
5,324,050, which is herein incorporated by reference. 
Additionally, means for conducting coolant fluid through the collet, 
particularly through longitudinal channels defined within the collet is 
described in U.S. Pat. No. 4,405,155, which is also incorporated herein by 
reference. 
Referring particularly to FIG. 3, collet 44 includes a coating 32 of solid 
film lubricant on at least the outer exposed faces 58 of jaw blades 50. 
For ease of applying coating 32, the coating may be applied to the other 
surfaces of jaw blades 50 as well, except for inner faces 54 which engage 
tool shank 68. 
The thickness of film 32 applied to the outer faces 58 of jaws 50 is 
preferably within the range of 0.0001 and 0.0005 inches. 
The present inventive tool holding device has been described primarily by 
reference to a chuck device and collet system. However, this is not meant 
to limit the invention in any way. The present invention is applicable to 
any manner of tool holding devices wherein an actuating mechanism 
comprises frictionally engaging metallic surfaces. Thus, it will be 
apparent to those skilled in the art that various modifications and 
variations can be made in the present apparatus without departing from the 
scope or spirit of the invention. It is intended that the present 
invention cover the modifications and variations of this invention 
provided within the scope of their appended claims and their equivalents.