Cutter Entry Angle (Plunge Angle)
The angle between the feed direction of the cutting tool and the reference surface of the work piece when cutting into the material is referred to as tool entry angle. This angle significantly influences the radial and axial stress on the machine spindle and the cutting tool during the chip removal process. The following information can be used as starting values for your configuration.
The spindle bearings of high speed motor spindles for milling applications are generally designed for high speeds and enduring high radial loads. Axial cutting loads should be kept as low as possible, though to ensure a long service life and optimum tool life. Therefore, the specified tool entry angles should be as low as possible. For spindles vertically mounted to the machine table, the tool entry angle should be between 0° and 20º. The lower the entry angle, the higher the feed rates. Using an entry angle below 20°, the maximum feed rate can be kept for the most applications. If the milling process requires a steep entry angle, the feed rate must be reduced accordingly to minimize the axial stress preventing damage to the spindle bearing. Refer to the chart below with regards to the different entry angles in relation to the percentage reduction of the feed rate. By using low entry angles, axial forces can be reduced and bearing life can be extended. If vertical plunging routines producing high axial loads are inevitable for your application, PDS offers special spindles for these applications.