... apply it to the production line, especially in the key craft work. Meanwhile, various patents of the craftworks and inventions guarantee ... of the products.Tapered Drill BitType --Chisel Bits / Cross Bits / Button Bits Diameter---28mm,30mm 32mm,34mm,36mm,40mm,42mm,44mmThread ... . Integral Drill Rod---H19/H22, Diameter---20mm - 42mm. T51 Thread button bits