LATHE OPERATIONS - OD1645 - LESSON 1/TASK 1
American Standard Machine tapers, the Jarno tapers, and the Standard taper
1 Morse tapers are used on a variety of tool shanks, and
exclusively on the shanks of twist drills. The taper for different numbers
of Morse tapers is slightly different, but is approximately 5/8 inch per
foot in most cases.
2 Brown and Sharpe tapers are used for taper shanks on tools such
as end mills and reamers, the taper being approximately 1/2 inch per foot
for all sizes except for taper No. 10, where the taper is 0.5161 inch per
3 The American Standard Machine tapers are composed of a self-
holding series and a steep taper series.
The self-holding taper series
consists of 22 sizes.
The name "self-holding" has been applied where the
angle of the taper is only 2 or 3 and the shank of the tool is so firmly
seated in its socket that there is considerable frictional resistance to any
force tending to turn or rotate the tool in the holder. The self-holding
tapers are composed of the selected tapers from the Morse, the Brown and
Sharpe, and the 3/4 inch per foot Machine taper series. The smaller sizes
of the self-holding tapered shanks are provided with a tang to drive the
cutting tool. Larger sizes employ a tang drive with the shank held with a
draw bolt. The steep machine tapers consist of a preferred series and an
intermediate series. A steep taper is defined as a taper having an angle
sufficiently large to insure the easy or self-releasing feature.
tapers have a 3 1/2 inch taper per foot and are used mainly for aligning the
milling machine arbors and spindles, and on some lathe spindles and their
4 The Jarno taper was originally proposed by Oscar J. Beale of the
Brown and Sharpe Mfg. Co. This taper is based on such simple formulas that
practically no calculations are required when the number of taper is known.
The taper per foot for all Jarno tapers is 0.600 inch per foot.
diameter at the large end is as many eighths, the diameter at the small end
is as many tenths, and the length as many half-inches as indicated by the
number of the taper.
For example: A No. 7 Jarno taper is 7/8 inch in
diameter at the large end; 7/10