Tapping collet

A tapping collet is actuated by engagement with a mating surface of a collet holder for holding a tap having a round shank portion and a square shank portion. The collet has a plurality of independent gripping jaws circumferentially disposed at essentially 90 degree intervals about a centerline axis through the collet. The gripping jaws have an inner face parallel to the centerline axis and an outer face which defines an outer surface for engaging a collet holder mating surface. Resilient material is disposed between the gripping jaws for holding the jaws in the desired spaced relation. The gripping jaws comprise a step portion which extends radially inward and defines a second inner diameter opening to engage the flat sides of the square shank portion of a tap inserted into the collet. The continuous outer diameter seal is disposed circumferentially about the outer surface of the collet and a continuous inner diameter seal is disposed circumferentially within a first inner diameter opening of the collet.

BACKGROUND OF THE INVENTION 
The present invention relates to machine collets, and more particularly to 
a collet for use with taps. 
As understood in the art, conventional taps require a relatively high 
degree of rotational torque for operation. Thus, the tool holding device, 
such as a tap collet, must be able to transmit the high rotational torque 
to the tapping tool. The tap itself has a round shank portion and a 
multi-sided rear shank portion. Typically, the multi-sided portion 
comprises a square profile. Split steel tap collets are known in the art 
for positively driving a tap having a tap square as described above. 
Kennametal, Inc. of Latrobe, Pa., manufactures and sells such a split 
steel tap collet. The conventional split steel tap collets, however, have 
a significant drawback in that they are relatively ineffective as sealing 
collets in situations wherein it is desired to conduct a coolant fluid to 
the tap through the collet. Due to the open spaces between the split steel 
gripping surfaces and the open sides of the square portion of the tap 
corresponding to the tap square, an effective seal cannot be obtained with 
this type of split steel tap collet. In many applications, it is highly 
desirable to conduct a relatively high pressure coolant fluid to the 
working surfaces of the tap through the collet and associated tool holder. 
Conventional split steel collets have proven relatively ineffective in 
this situation. 
The Jacobs.RTM. Chuck Manufacturing Company manufactures and markets a well 
known Rubber-Flex.RTM. collet of the type having a plurality of individual 
independent gripping members held in position and equally spaced about a 
common axis. The spaces between the gripping members is filled with an 
adherent resilient material, such as rubber or a rubber composition. The 
benefits of the Rubber-Flex.RTM. collet over conventional split steel 
collets in both gripping strength and in sealing applications are well 
known to those skilled in the art. However, it was previously not thought 
of to utilize a Rubber-Flex.RTM. collet as a tap collet due to the 
relatively high rotational torque required for tap collets. Thus, the 
benefits of a Rubber-Flex.RTM. collet have generally not been recognized 
or appreciated in the tap collet line. 
OBJECTS AND SUMMARY OF THE INVENTION 
It is therefore a principal object of the present invention to provide an 
improved sealing tap collet. 
It is a further object of the present invention to incorporate the benefits 
of a Rubber-Flex.RTM. collet with a tap collet. 
And yet another object of the present invention is to provide a sealing 
collet which allows for the induction of relatively high pressure coolant 
fluid to the working surfaces of a tap. 
A still further object of the present invention is to provide a 
Rubber-Flex.RTM. collet having the capability to transmit the high 
rotational torque required in tapping operations. 
Additional objects and advantages of the invention will be set forth in 
part in the following description, or may be learned through practice of 
the invention. The objects and advantages of the invention may be realized 
and attained by means of the instrumentalities and combinations 
particularly pointed out in the appended claims. 
In accordance with the objects of the present invention, a machine tool 
tapping collet is provided which is actuated by engagement with a mating 
surface of a collet holder. Actuation of a collet with a collet holder is 
well understood by those skilled in the art. The collet includes a 
plurality of independent gripping jaws held in a desired longitudinally 
and equally spaced angular position about a longitudinal centerline axis 
through the collet. The gripping jaws have an inner face parallel to the 
centerline axis and an outer face whereby the plurality of gripping jaws 
define an outer surface for engaging the collet holder mating surface. 
Resilient material is disposed between the gripping jaws for holding the 
jaws in the desired spaced relation. The gripping jaw inner faces further 
define a first inner diameter opening for receipt of the round shank 
portion of a conventional tap. The gripping jaws further define a second 
inner diameter opening in axial alignment with the first inner diameter 
opening for receipt of the square tap shank portion. In this manner, the 
gripping jaws are circumferentially disposed at essentially 90 degree 
intervals about the centerline axis. The gripping jaw inner faces further 
comprise a step portion which extends radially inward and defines the 
second inner diameter opening. The gripping jaw inner faces at the second 
inner diameter opening engage the flat sides of the square shank portion 
inserted into the collet. The collet further includes an outer diameter 
seal disposed circumferentially about the outer surface and which extends 
circumferentially radially outward beyond the outer faces of the gripping 
jaws. The collet further includes a continuous inner diameter seal 
disposed circumferentially within the first inner diameter opening and 
extending circumferentially radially inward beyond the inner faces of the 
gripping jaws. 
In a preferred embodiment of the invention, the collet comprises at least 
four gripping jaws, with one gripping jaw disposed at each 90 degree 
interval. In an alternative preferred embodiment, pairs of gripping jaws 
are disposed at the 90 degree intervals. 
Preferably, the continuous inner diameter seal is formed integral with the 
resilient material and the continuous outer diameter seal is also formed 
integral with the resilient material. Preferably, the inner and outer 
diameter seals comprise double lip seals and are molded integral with the 
resilient material. 
It is also preferred that each gripping jaw further comprise at least one 
perforation defined therethrough. The resilient material extends through 
these perforations and forms essentially concentric rings of resilient 
material through the gripping jaws. 
The collet also preferably includes longitudinal channels which are defined 
in the resilient material between the gripping jaws. These longitudinal 
channels define coolant induction ports wherein coolant is conveyed within 
the collet up to the inner diameter seal. 
The step portion of the gripping jaw inner faces at the second inner 
diameter opening preferably comprises a longitudinal section of gripping 
jaw inner face which is longitudinally parallel to the gripping jaw inner 
face at the first inner diameter opening. The step portion in this 
embodiment is defined by a ridge of the gripping jaw which extends 
radially inward and perpendicular to the inner faces. 
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, 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. 
Referring to FIG. 1 in particular, a tap collet 10 is provided. Collet 10 
includes a plurality of gripping jaws 18 held in a desired spaced relation 
relative to each other and the longitudinal centerline 20 (FIG. 2) through 
the collet. Gripping jaws 18 are held in place by resilient material 28 
between each gripping jaw. Material 28 also preferably extends through 
perforations 42 within gripping jaws 18 so as to form essentially 
concentric rings of resilient material 44 through gripping jaws 18. 
Collet 10 is designed to hold a conventional tap having a round shank 
portion 14 and a square shank portion 16, as illustrated in FIG. 3. Such 
taps are well known in the art. and a detailed explanation of the tap is 
not necessary for purposes of the present disclosure. The gripping jaws 18 
are disposed around longitudinal centerline axis 20 such that the inner 
faces 22 of jaws 18 define a first inner diameter opening 30 for receipt 
of round shank portion 14 of tap 12. Likewise, jaw inner faces 22 also 
define a second inner diameter opening 32 in axial alignment with first 
inner diameter opening 30 for receipt of the square shank portion 16 of 
tap 12. In this regard, jaws 18 are circumferentially disposed at 
essentially 90 degree intervals about centerline axis 20, as generally 
illustrated in the figures. Accordingly, collet 10 includes at least four 
gripping jaws 18, and preferably includes at least pairs of gripping jaws 
18 disposed at 90 degree intervals as particularly illustrated in the 
figures. Thus, the jaw inner faces 22 contact and grip round shank portion 
14 of tap 12 within the first inner diameter opening 30. In the embodiment 
wherein pairs of jaws are utilized at the 90 degree intervals, jaws 18 are 
disposed parallel to each other such that the inner faces 22 define an 
essentially flat or horizontal line of contact against the tap shank, as 
will be more fully explained below. 
Gripping jaws 18 comprise a step portion 34 which extends radially inward 
from first inner diameter opening 30. Step portion 34 essentially defines 
the second inner diameter opening 32. Thus, step portion 34 extends radial 
inward such that the inner faces of jaw blades 18 within second diameter 
opening 32 will contact and engage the flat sides of the multi-sided or 
square shank portion of tap 12. 
Step portion 34 is preferably defined by a ridge 48 formed in jaw blades 
18. Ridge 48 extends perpendicular to inner jaw faces 22. As clearly seen 
in FIGS. 1 and 2, jaw blades 18 comprise a longitudinally extending 
section rearward of ridge 48. These longitudinally extending sections 
essentially define second inner diameter opening 32. Thus, inner diameter 
opening 32 comprises at least one jaw blade, and preferably two parallel 
jaw blades, to contact each side of the square shank portion 16 of tap 12. 
It should thus be understood that the inner faces 22 of jaw blades 18 
within first inner diameter opening 30 are disposed at a radial distance 
from the longitudinal centerline 20 so as to contact and grip on the outer 
circumference of round shank portion 14. The flat sides of square shank 
portion 16 of tap 12 are radially inward of the circumference of the round 
shank portion 14 and, thus, the inner faces 22 of jaw blades defining 
second inner diameter opening 32 extend radially inward from the inner 
faces defining first inner diameter opening 30. Preferably, the inner 
diameter faces 22 in the first and second inner diameter openings are 
parallel. 
In order to insert tap 12 within collet 10, it is necessary for the 
operator to turn the tap until the square shank portion 16 is aligned with 
second inner diameter opening 32. 
Jaws 18 further include an angled exposed outer face 24 whereby the 
plurality of outer faces 24 define an essentially conical outer surface 26 
which matches a complimentary conical receiving surface of a collet holder 
(not shown). 
As depicted generally in the figures, in a preferred embodiment of the 
invention, resilient material 28 is generally flush with the outer exposed 
faces 24 of gripping jaws 18. However, this is not necessarily a 
limitation of the invention. In another embodiment of the invention, 
resilient material 28 may be defined generally below the exposed outer 
faces 24 of jaws 18. Compression recesses (not shown) may also be defined 
in the resilient material between jaw blades 18 to allow for greater 
compression of collet 10 within its respective mating collet holder. The 
necessity of compression recesses is dependent upon the resiliency and/or 
volume of resilient material between the respective gripping jaws 18. 
Referring particularly to FIG. 3, it is highly desirable in many 
applications of taps to conduct a coolant fluid to the cutting surfaces of 
tap 12 through coolant port 13 defined through tap 12, as understood in 
the art. In this regard, collet 10 further includes a continuous outer 
diameter seal 36, as particularly shown in FIGS. 1 and 3. Outer seal 36 is 
formed preferably integral with resilient material 28 and is also formed 
of the same material as resilient material 28. In this manner, outer seal 
36 is molded integral with resilient material 28. In a preferred 
embodiment of the invention, outer seal 36 comprises a double lip seal 40, 
as indicated in FIG. 1. In an alternative embodiment, seal 36 may comprise 
a single lip. 
Collet 10 also includes a continuous inner diameter seal 38, as illustrated 
in the figures. Seal 38 is also preferably formed integral with resilient 
material 28 and, in a preferred embodiment, also comprises a double lip 
seal 40 as illustrated particularly in FIG. 1. Again, this double lip seal 
is also preferably molded integral with resilient material 28. 
The design and operation of the continuous inner and outer diameter seals 
of the present tapping collet are discussed extensively in my U.S. Pat. 
No. 5,324,050, which is herein incorporated by reference. 
Referring particularly to FIG. 4, the present collet 10 also preferably 
includes longitudinal channels 46 defined in resilient material 28 from 
the back end or surface of collet 10 essentially to the inner diameter 
seal 38. Channels 46 serve the dual purpose of allowing for greater 
compression of collet 10 and also for conducting coolant fluid within 
collet 10. For example, in a conventional tap wherein a coolant channel is 
defined through the tap, relatively high pressure coolant fluid can be 
introduced to collet 10 within a collet holder. The coolant fluid is 
prevented from leaking around the collet 10 by means of the continuous 
outer diameter seal 36 and is prevented from leaking through the collet by 
means of continuous inner diameter seal 38. The coolant will be contained 
within collet 10 and directed to the channel or hole defined through the 
tap tool. Alternatively, the coolant may be directed from within collet 10 
to a work piece by means of a coolant port defined through the front face 
of the collet and in communication with the longitudinal channels 46. This 
embodiment is described in my U.S. Pat. No. 5,405,155 which is also 
incorporated herein by reference. 
The present inventive tapping collet 10 offers several distinct advantages 
over conventional tapping collets. For example, collet 10 has a far 
greater degree of compressibility as compared to a split-steel collet. 
Thus, a single collet 10 may be used for two different sized taps whereas 
two split-steel collets would be needed. The sealing capabilities of 
collet 10 also cannot be achieved by conventional tapping collets. 
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. Thus, it is intended that the 
present invention cover the modifications and variations of this invention 
provided they come within the scope of the appended claims and their 
equivalents.