This invention is directed to a holder for a recess cutting tool. The holder is used with a multiple spindle machine tool having several spindles that are positioned to hold a workpiece. The tool holder is designed to adjust to variations, and compensate for wear, in the spindles that are used to hold the workpiece while the recessed cut is being made.
Because of the basic design of this tool holder, normal tool change adjustments are mush faster and accurate. Also, in some recess cutting operations, more dwell time is necessary than normally provided. This tool holder can accomodate the extra dwell time without affecting any other tool or tool holders used in the multiple spindle machine tool.
Multiple spindle machine tools have been known and used for several years to perform machining operations on various types of workpieces. The multiple spindle machine tools have a plurality of rotatable spindles that are positioned to hold the workpieces so that cutting tools can perform various machining operations on the workpiece. Normally, the spindles are positioned on a rotating spindle carrier and the workpiece is indexed to various work stations on the multiple spindle machine tool. Various machining operations can be performed at each of the work stations. In this manner one multiple spindle machine tool can perform several machining operations on a workpiece.
The spindles are usually rotatably supported by bearings in the rotating spindle carrier. During the course of use, the bearing housings for the individual spindles become worn. This is particularlly true where the machining operations produce heavy loads on the workpiece that must be absorbed by the supporting bearings. The wear on the bearings is not always uniform as the workpiece rotates during the machining operations. In addition, the wear on the bearing housings of the individual spindles is not uniform and the spindles at different positions on the multiple spindle machine tool will have different locations around the centerline of the rotating carrier. Thus, as the multiple spindle machine tool indexes to a new work station the spindle that is moved into that work station will not have the same centerline as the other spindles that have been indexed to that work station. Accordingly, it is particularly difficult to maintain close tolerances when performing various machining operations on such a multiple spindle machine tool. The closer the tolerance requirements the more difficult it is to utilize a multiple spindle machine tool where the bearings for the spindles have become worn.
The above difficulties are compounded when a recess cut is to be made in a workpiece. A recess cut or machining operation takes place inside a passageway or opening in the workpiece. It is necessary to precisely position the cutting tool at the right location in the opening in the workpiece and then move the cutting piece radially outward to make the recess cut. To hold close tolerances on such a recess cut it is necessary to precisely position the cutting tool with respect to the workpiece. This is particularly difficult to do if the spindle that is supporting the workpiece has worn bearings. As the workpiece is rotated to make the recess cut the worm bearings will allow the workpiece to wobble slightly and prevent the cutting tool from making the recess cut with the precision desired. Since the recess cut is being made on the interior of the workpiece, it is also extremely difficult to check or maintain tolerances while the cutting operation it taking place. Normally, the recess cut is not even visible to the operator of the multiple spindle machine tool.
As multiple spindle machine tools begin to lose precision as the bearing housing become worn the machine can no longer be used for close tolerance precision work. When this occurs, the usefulness of the machine is greatly reduce as the machine can only be used to perform machine operations that do not require a great deal of precision. In addition, the owner of the machine tool was faced with buying a new machine tool to continue to do precision work. Thus, the wear on the bearing housings that support the spindles on the multiple spindle machine tool greatly effect the useability and useful life of such machining equipment.
Accordingly, there is a need in the industry for a multiple spindle machine tool that can correct for wear that developes in the spindles that support the workpiece upon which the machining operations are being performed. It is also desirable to have a mechanism that will compensate for the different wear that developes on each individual spindle of the multiple spindle machine tool. It is also desirable to have a correction mechanism that can accomodate additional wear on the spindles that takes place as the multiple spindle machine tool receives additional use and wear-to-tear. The above considerations are particularly important if a multiple spindle machine tool is to be used for high precision work over an extended period of time.