Small Hole Boring Catalogue Numbering System A/B Series Boring Bar Identification System Each character in our catalogue number signifies a specific trait of that product. Use the following key columns and corresponding images to easily identify which attributes apply. ATBM838 AT B M 8 38 Series Style and Bar Type Boring Type Shank Diameter Length Construction Features Bar shown as “D” shown as “L” of the Boring Bar AT = Through Coolant M = Metric Metric Metric 8 = 8,00mm 38 = 38,0mm BS = No Coolant 10 = 10,00mm 100 = 100,0mm 12 = 12,00mm 102 = 102,0mm 16 = 16,00mm 152 = 152,0mm 20 = 20,00mm L widia.com D61