Section One of this Standard relates to a series of tapers having an angle sufficiently large to ensure quick- or self-release and intended primarily for use on the spindle noses and arbors of milling machines. Basic dimensions are specified for four sizes of quick-release tapers and the essential dimensions of spindle noses and arbors incorporating these tapers are also given. Section Two provides for gauges suitable for checking quic-release tapers on spindle noses and arbors.