asymmetric features to minimize imbalance and vibration. ASME B5.62 "Hollow Taper Tooling With Flange-Face Contact" and ISO 12164-3:2014 "Dimensions of shanks for stationary tools" include an additional form T, which is bidirectionally compatible with form A, but has a much tighter tolerance on the widths of the keys and keyways used for angular alignment. This permits non-rotating lathe tooling to be held accurately. An HSK connection depends on a combination of axial clamping forces and taper-shank interference. All these forces are generated and controlled by the mating components' design parameters. The shank and spindle both must have precisely mating tapers and faces that are square to the taper's axis. There are several HSK clamping methods. All use some mechanism to amplify the clamping action of equally spaced collet segments. When the toolholder is clamped into the spindle, the drawbar force produces a firm metal-to-metal contact between the shank and the ID of the clamping unit. An additional application of drawbar force positively locks the two elements together into a joint with a high level of radial and axial rigidity. As the collet segments rotate, the clamping mechanism gains centrifugal force. The HSK design actually harnesses centrifugal force to increase joint strength. Centrifugal force also causes the thin walls of the shank to deflect radially at a faster rate than the walls of the spindle. This contributes to a secure connection by guaranteeing strong contact between the shank and the spindle. The automotive and aerospace industries are the largest users of HSK toolholders. Another industry that is seeing increasing use is the mold and die industry. R8 This taper was designed by Bridgeport Machines, Inc. for use in its milling machines. R8 tapers are not self-holding, so they require a drawbar extending up through the spindle to the top of the machine to prevent loosening when lateral forces are encountered. They are also keyed (see image) to prevent rotation during insertion and removal, although it is the taper that transmits torque in use. The drawbar thread is typically ″–20 tpi (UNF). The angle of the cone is 16°51′ (16.85°) with an OD of 1.25″ and a length of ″. (source, Bridgeport Manufacturer) The diameter of the parallel locating portion is not a "fractional inch" size like the other dimensions and is 0.949″ to 0.9495″. Tools with an R8 taper are inserted directly into the machine's spindle. R8 collets are typically used