Union Butterfield 4531 High-Speed Steel Expansion Chucking Reamer, Straight Flute, Round Shank, Uncoated (Bright), 3/8 inch Expandable as wear decreases its cutting diameter, so it can be reground and re-sharpened to its original dimensions for increased life Morse taper shank for accurate alignment and firm hold in the socket of a toolholder Straight flute for general-purpose reaming of uninterrupted cuts in through holes and blind holes Uncoated (bright) tools have no additional surface treatment or coating, suitable for general-purpose applications 45-degree bevel at the cutting tip facilitates entry to pre-drilled holes