Chatter or vibrations during boring operations is generally because of instability between the cutting tool ad workpiece. Often applying a larger-diameter boring bar will eliminate the problem. However, when a larger bar is not an option, there are options to reduce chatter that can reduce productivity and affect workpiece quality.
The solution could be adjusting cutting speeds and chip loads to change the cutting pressure on the tool. You can adjust the tool pressure by increasing the feed rate and decreasing the cutting speed, both at the same time or changing the radial DOC. It may take adjustments of all these variables to decrease chatter.
The chatter-causing problem could be the tool holder. Basic tool holders do not always offer the accuracy or rigidity for high-performance machining. A tool holder shank that provides simultaneous contact between the precision ground spindle face and spindle taper will increase rigidity and aids damping. Keep in mind, it is best to balance at the highest expected spindle speed to improve surface finishes.
To avoid chatter, be sure the cutting tool has the correct coating, substrate, geometry, and length-to-diameter ratio for the application. You can also use cutting tools with variable-flute geometries to reduce chatter.
A part improperly secured to the workholder can vibrate and cause chatter. Factors to consider when selecting the workholder include the clamping force, accuracy, and ease of use with the workpiece.
Lastly, a poorly maintained machine will only increase the chance of chatter. Regular maintenance needs to be conducted to ensure the best performance of the equipment to avoid this issue, as well as others.