to hold tooling with round shanks, although any shape can be held if the collet has the corresponding shape cut in it. The collets have a precision bore with axial compression slots for holding cutting tools and are threaded for the drawbar. The R8 system is commonly used with collets ranging in size from ″ to ″ in diameter or tool holders with the same or slightly larger diameters. The collets or tool holders are placed directly into the spindle and the drawbar is tightened into the top of the collet or tool holder from above the spindle. Other tools such as drill chucks, fly cutters, indexable insert cutters, etc. may have an R8 taper shank built into or added to the tool. The R8 taper is commonly encountered on Bridgeport and similar turret mills from the USA, or on (very common) copies of these mills from elsewhere. The popularity is due in large part to the success of Bridgeport and other mills that were closely modeled after it and produced throughout much of the 20th century. See also Chuck Collet References Sources External links Beautiful Iron Overview of Tapers Quickly Identify your Morse Taper http://www.tools-n-gizmos.com/specs/Tapers.html (description of several tool holders) https://web.archive.org/web/20110316155700/http://www.timgoldstein.com/CAD_CAM/tapers.htm (description of several tool holders) http://www.dlindustrial.com/profiles/blogs/steep-tapers-fast-tapers-at3-and-what-it-means (blog about holding/releasing tapers and tolerance; claims taper not keys and slots do the driving; some errors) Machine tools Woodworking