... significantly longer tool life, precise engraving·Specifically designed to engrave 3D Relief on marble ,granite ,sandstone , ... bit is most important for working with CNC Router Machine. How to select a good engraving bit supplier???1. Select ... wood!!!2. Bit supplier can test bit with CNC Machine. If Bit supplier can't ... . If not, when clients have any questions with using bit, who could help them???4. ...