Morse taper
shanks and sockets

One of several standards for taper shanks on twist drills, reamers, and other rotating tools, and for the matching socket on a lathe, milling machine, drill press, and so forth. Taper shanks are cone-shaped. One advantage of such an arrangement is that it centers the tool very accurately. For shanks of the size and with the degree of taper in the Morse series, friction alone is enough to turn the tool and to hold the shank in the socket.

drill bit with a morse taper socket

At the end of the shank is a flat protrusion called the “tang” or (older usage) “tongue”. To release the shank from the socket, a wedge (a key with a taper of 1.75 in 12) is tapped through a keyway at the bottom of the socket. It pushes on the bottom of the tang and frees the tool.

drift key for removing a tool from a morse taper socket

Morse taper originally was thought of as 5/8 inch per foot (0.625). As precision improved, it was realized that the existing patterns did not quite conform to this ideal. Rather than orphan equipment already in use, the slightly-off specifications have continued to be used.

inches per
diameter of 
end of socket
length of shank,
to bottom of tang
plug depth
MT 0 0.62460 0.3561 2 11/32 2
MT 1 0.59858 0.475 2 9/16 2 1/8
MT 2 0.59941 0.700 3 1/8 2 9/16
MT 3 0.60235 0.938 3 7/8 3 3/16
MT 4 0.62326 1.231 4 7/8 4 1/16
MT 5 0.63151 1.748 6 1/8 5 3/16
MT 6 0.62565 2.494 8 9/16 7 1/4
MT 7 0.62400 3.270 11 5/8 10

This data is provided to enable readers to identify a tool. For detailed specifications, consult a reference such as Machinery's Handbook.

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