BT - CENTER ALIGNMENT SHANK AND BASE - METRIC FOR SPECIALLY TAILORED TOOL HOLDERS Taper SizeBT-40 and 50 AT3 Taper 58-60 HRc N5 L L1 L2 (1) D1 D G D2 Designation L L1 L2 D D1 D2 G Hex key(1) ADJ BT40 D70 55 28 18 70 35 62.5 M16 4 ADJ BT50 D70 70 32 - 70 35 - M24 4 814