Patent Application
20160167188
The present invention relates to tool holder assemblies and, in particular, to tool holder assemblies employing a collet.
Tool holder assemblies and collets configured for use with interchangeable cutting or machining tools provide a number of process efficiencies. A smaller number of machine spindles, for example, can be employed for a larger variety of machining operations, and downtime between various cutting tasks can be reduced by decreased need to switch apparatus for each machining application. Additionally, mechanical working of a cutting tool or cutting tool blank to provide or restore one or more cutting edges similarly benefits from such process efficiencies. In order to realize the foregoing efficiencies, tool coupling systems and spindle connector assemblies must provide secure connection with minimal tool change downtime while maintaining desired operating tolerances.
Several approaches to securely retaining tools for rotary cutting applications utilize reducer sleeves or collets for receiving differently sized or shaped tool shanks. Reducer sleeves and/or collets, however, can present deficiencies in maintaining tolerances for radial runout and grip. Tool holder assembly design continues to evolve in response to the changing demands of tool making and machining applications, thereby calling for the development of new tool holder configurations
In one aspect, collets are described herein employing a central bore having a stepped architecture. For example, a collet described herein comprises a clamping portion having a central bore for receiving a coupling portion of a cutting tool or cutting tool blank. The central bore has a stepped architecture comprising an inner section of first diameter, a transition section of second diameter, and an outer section of third diameter. In some embodiments, the inner section is the innermost stepped section of the collet. Similarly, in some embodiments, the outer section is the outermost stepped section of the collet.
In another aspect, tool holder assemblies are described herein. A tool holder assembly comprises a housing, a collet, and a cutting tool or cutting tool blank having a coupling portion. The housing defines a socket and is configured or adapted for connection and rotation with a spindle about an axis of rotation. The collet is, positioned in the socket and includes a clamping portion having a central bore of stepped architecture. The stepped architecture of the central bore comprises an inner section of first diameter, a transition section of second diameter, and an outer section of third diameter. The cutting tool or cutting tool blank has a coupling portion positioned in the central bore such that the surfaces of the inner section and transition section engage the coupling portion. In some embodiments, the inner section is the innermost stepped section of the collet and the outer section is the outermost stepped section of the collet.
In a further aspect, methods of making cutting tools are described herein. A method comprises providing a cutting tool blank having a coupling portion and a blank portion and securing the coupling portion of the cutting tool blank in a clamping portion of a collet. The clamping portion of the collet has a central bore of stepped architecture comprising an inner section of first diameter, a transition section of second diameter, and an outer section of third diameter. The method further comprises grinding the blank portion to provide a working portion of the cutting tool having one or more cutting edges.
Embodiments described herein can be understood more readily by reference to the following detailed description and examples and their previous and following descriptions. Elements and apparatus described herein, however, are not limited to the specific embodiments presented in the detailed description. It should be recognized that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptations will be readily apparent to those of skill in the art without departing from the spirit and scope of the invention.
Referring now to
As illustrated in
A collet (100) described herein comprises a central bore (120) having a stepped architecture. As illustrated in
Further, in some embodiments, the central bore of a collet described herein can terminate in a tapered surface. Such a configuration may be adapted or configured to engage a complementary tapered portion on a cutting tool or cutting tool blank.
Collets described herein can provide certain performance characteristics or to conform to tolerance ranges. For example, a collet can be configured to have a runout error within a desired range when engaging a cutting tool or cutting tool blank. For the purposes of the present disclosure, runout error is determined by measurement at a distance of 2(d) from a front end of the collet, wherein d is the diameter of the cutting tool or cutting tool blank. A collet can provide any runout error value not inconsistent with the objectives of the present invention. For example, collet runout error can be selected from Table I.
In another aspect, tool holder assemblies are described herein. Referring now to
As illustrated in
A coupling portion (210) of the cutting tool or cutting tool blank (200) can further comprise a convex tail (214). As illustrated in
In a further aspect, methods of making cutting tools are described herein. A method of making a cutting tool comprises providing a cutting tool blank having a coupling portion and a blank portion, securing the coupling portion of the cutting tool blank in a clamping portion of a collet, and grinding the blank portion to provide a working portion of the cutting tool having one or more cutting edges. The clamping portion of the collet has a central bore of stepped architecture comprising an inner section of first diameter, a transition section of second diameter, and an outer section of third diameter. Surfaces of the inner section and the transition section of the collet can engage the coupling portion of the cutting tool blank. Further, the transition section can engage a threaded section of the coupling portion. A radial clearance can be provided between the outer section and the coupling portion.
Individual steps of methods described herein can be carried out in any order or in any manner not inconsistent with the objectives of the present invention. Further, any additional steps can be carried out consistent with the present invention. For example, the method can further comprise grinding flutes in the working portion in addition to or in combination with the one or more cutting edges. In some embodiments, the cutting tool blank is rotated during grinding. An example of a portion of a method described herein is illustrated in
Various embodiments of the invention have been described in fulfillment of the various objects of the invention. It should be recognized that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptations thereof will be readily apparent to those skilled in the art without departing from the spirit and scope of the invention.
