1. Field of the Invention
The present invention relates in general to a tool holder suitable for use on a machine tool with an automatic tool change device, and more particularly to such a tool holder which is capable of automatically adjusting or compensating the radial position of a cutting tool thereon by utilizing the rotation of a tool spindle receiving the tool holder.
2. Description of the Prior Art
Generally, a boring tool holder, as used in a machine tool with an automatic tool change device, incorporates a tool position compensating mechanism therein. This compensating mechanism serves to adjust the position of a cutting tool, carried on the tool holder, in a radial direction thereof by utilizing the rotation of a tool spindle. Such a compensating mechanism utilizes, for example, a thread mechanism to convert rotational movement of the tool holder into axial movement, and a tapered cam mechanism to convert the axial movement into a radial movement which is finally transmitted to the cutting tool. With this type of tool position compensating mechanism, a unit compensating amount of the cutting tool per single rotation of the spindle can be set by pitch of the thread mechanism and the gradient of the tapered cam mechanism. However, since the pitch and the gradient are naturally limited in accuracy, it is extremely difficult to adjust the position of the cutting tool within an accuracy of micron order.
For this reason, utilization of a ratchet mechanism may be considered to transmit the rotation of the spindle a unit angle by a unit angle. However, the ratchet mechanism can transmit the rotation of the spindle only in one direction, so that the position of the tool cannot be freely adjusted depending upon the size of a machined bore. Moreover, when the tool is worn out to be replaced by a new one, the tool holder has to be disadvantageously disassembled to restore the tool position compensating mechanism to its original state.