BT - SHORT ER COLLET CHUCK - METRIC Taper SizeBT 30, 40 and 50 A ➚ A .003 AT3 Taper 58-60 HRc N5 G2.5 LRef L1Ref 20,000 RPM G1 D G J Designation Range L L1 D J G G1 BT30 ER20 SHORT 1-13 27.2 5.2 25 M12 M12 M25x1.5 BT40 ER32 SHORT 2-20 36.5 9.5 40 M16 M16 M40x1.5 BT40 ER40 SHORT 3-26 46.5 9.5 50 M16 M16 M50x1.5 BT50 ER32 SHORT 2-20 47.5 9.5 40 M22x1.5 M24 M40x1.5 BT50 ER40 SHORT 3-26 47.5 9.5 50 M28x1.5 M24 M50x1.5 Add B for coolant through the flange 803