Cutting by use of rotating axially moving tool – Tool-carrier with vibration-damping means
Patent
1997-01-17
1998-12-15
Howell, Daniel W.
Cutting by use of rotating axially moving tool
Tool-carrier with vibration-damping means
408144, 408223, B23B 4700
Patent
active
058488618
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an elongated tool-bit holder having vibration damping properties and a unique placement of bits.
BACKGROUND ART
A tool-bit holder with vibration-damping properties is disclosed in GB patent specification No. 1,299,750. With a view to achieving the vibration-damping properties, the tool-bit holder thus known is divided into two mutually coaxial rigid parts with an intermediate layer of "anti-vibration material", such as rubber. It will be obvious that, compared to the manufacturing of conventional tool-bit holders, known normally to be manufactured in one single piece of material, this construction causes a considerable increase in the cost of the manufacturing process.
Other attempts at changing the vibration characteristics of tool holders with a view to preventing instability or "chatter" are disclosed in U.S. Pat. Nos. 4,553,884 and 4,903,785. According to the former of these two specifications, an absorber package tuned to a particular frequency is inserted in the tool shaft, thus avoiding chatter at that particular frequency. According to the latter specification, a shank is divided so as to raise its "natural" frequency. Apart from being limited in their range of frequencies, these designs are expensive to manufacture and require careful adjustment to operate properly.
Further, U.S. Pat. No. 5,237,895 discloses a method of preventing "chatter" by supplementing the normal mechanical clamping with fluid-pressure clamping. Obviously, this design also is expensive and requires careful adjustment.
Further still, EP-A2-0,313,044 and DE-A1-4,324,869 disclose tool bits with a geometry intended to reduce chatter. Thus, these publications do not deal with the question of damping vibrations.
Finally, DE-A1-3,600,077 discloses an end-milling tool, in which the geometry of the bits enable the tool to be used for milling both in the axial and in the transverse directions. The question of vibrations is not dealt with.
DISCLOSURE OF THE INVENTION
On this background, it is the object of the invention to provide a tool-bit holder of the kind referred to initially, with which it is possible to achieve vibration-damping properties by extremely simple means, and this object is achieved by means of the feature set forth hereafter. By manufacturing the tool-bit holder in the form of one single piece of homogeneous material with known, not inconsiderable vibration-damping properties, a manufacturing process is achieved, that is no more complicated or expensive than the process of manufacturing the conventional tool-bit holders from e.g. tool steel, which--as is well known--possesses very low vibration-damping properties. At the same time, the vibration-damping effect as achieved with the arrangement of said GB patent specification No. 1,299,750 is retained.
It will be evident that a tool-bit holder manufactured from a material with considerably lower surface hardness than the hitherto known materials, such as tool steel, will be more vulnerable to wear from the chips produced during the machining of the workpiece concerned. This drawback is avoided by additionally providing the tool-bit holder with the feature set forth hereafter.
The invention also relates to a method of manufacturing a tool-bit holder according to the invention, and this method is characterized by the steps set forth hereafter. By proceeding in this manner, it is avoided that also the surfaces of the sockets, in which the tool bits are to be received, are given an increased surface hardness and consequently become less capable of "gripping" the bits.
Advantageous embodiments of the tool-bit holder and said method are also set forth hereafter.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following, the invention is explained in more detail with reference to the exemplary embodiments of tool-bit holders according to the invention shown in the drawing, in which
FIG. 1 is a front view in the direction of the arrow I in FIG. 2 of a drill in the form of a drill-bit holder with clamped-on tool bits, together
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"Metals Handbook Ninth Edition", vol. 1 Properties and Selection: Irons and Steels.
Bhargava Adesh
Howell Daniel W.
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