This is the part of the spindle that will hold and grip the end mill at the spinning part of the spindle. This is a collet for smaller spindles with the ER-11 specification. This collet will accept tools with a 1/4" (6.35mm) shank.
This collet has a high precision TIR (Total Indicated Runout) of 0.0002". The bore measures 1/4" .25 inch (6.35 mm) to hold end mills that have a 1/4" shank. The shank of an end mill is the smooth part of the end mill that is inserted into the collet of the end mill.
General dimensions for ER-11 collets:D (Outside Diameter): 0.453 inches (11.5062 mm)L (Overall Length): 0.709 inches (18.0086 mm)L1 (Front Tapered Length): 0.531 inches (13.4874 mm)L2 (Rear Tapered Length): 0.098 inches (2.4892 mm)
This Collet Bore Diameter (d): .25 inches (6.35 mm)