Sherline 45260 Extended Column Bed (15") 45260 Lead Screw Sold Separately By popular demand, particularly in the CNC market, Sherline now offers a 4" taller mill column bed and leadscrew. This extends the upward travel of your mill saddle by an additional 4", giving you over 10" of vertical travel. The column bed is offered in either manual or CNC versions. The CNC version has the two additional 8-32 stepper motor mount holes already drilled and tapped.