Standard & SPL Machine Taper
BT40/BT50/BBT/HSK/ISO

Tapers range from a Number 2 to a Number 20. The diameter of the big end in inches is always the taper size divided by 8, the small end is always the taper size divided by 10 and the length is the taper size divided by 2. For example, a Jarno No. 7 measures 0.875" (7/8) across the big end.The Morse Taper system was first introduced by the Morse Twist Drill and Machine Company and was based upon a taper-per-foot of 5/8 inch. In actuality, none of the Morse Tapers are exactly . 62500 per foot, but rather range from . 59858 to .