... , it is better chioce for re-grinding. If not, every bit could used only once. Warm promptly: if you use our ... tools for hard materials, such as stone, gravestone , ceramic tiles, glass, marble, etc. 2. Applicable engraving : Multifunctional, thin line-relief ,V ... the rapid developmewnt of Chinese Diamond Tools industry. D6-90 Straight Shank End Mill Bit for Engraving Machine