для заказа - kyocera@kyocera-tools.ru TERMS DEFINITIONS
TAPS ENGINEERING DATA
DEFINITION OF TERMS APPLYING TO TAPS
DRILLS ALLOWANCE HELIX ANGLE
END MILLS Minimum clearance between two mating parts; the prescribed The angle made by the advance of the thread as it wraps around
variations from the basic size. an imaginary cylinder.
ROUTERS
ANGLE OF THREAD HOOK
THREAD MILLS
& TAPS The angle included between the sides of the thread measured in The undercut on the face of the teeth.
an axial plane.
ENGRAVERS HOOK ANGLE
AXIS
BORING BARS The inclination of a concave cutting face, usually specified either
The imaginary straight line that forms the longitudinal center line as Chordal Hook or Tangential Hook.
REAMERS of the tool or threaded part.
Chordal Hook Angle: The angle between the chord passing
SAWS BACK TAPER through the root and crest of a thread form at the cutting face,
and a radial line through the crest at the cutting edge.
TECHNICAL A gradual decrease in the diameter of the thread form on a tap
from the chamfered end of the land towards the back which Tangential Hook Angle: The angle between a line tangent to
INDEX creates a slight radial relief in the threads. a hook cutting face at the cutting edge and a radial line to the
same point.
BASE OF THREAD
INTERRUPTED THREAD TAP
The bottom section of the thread; the greatest section between
the two adjacent roots. A tap having an odd number of lands with alternate teeth along
the thread helix removed. In some cases alternate teeth are
BASIC SIZE removed only for a portion of the thread length.
The theoretical or nominal standard size from which all variations LAND
are derived by application of allowances and tolerances.
The part of the tap body which remains after the flutes are
CHAMFER cut, and on which the threads are finally ground. The threaded
section between the flutes of a tap.
The tapering of the threads at the front end of each land of a
tap by cutting away and relieving the crest of the first few teeth LEAD
to distribute the cutting action over several teeth; Taper taps are
chamfered 7-10 threads; plug taps are chamfered 3-5 threads; The axial distance a tap will advance along its axis in one
bottoming taps are chamfered 1-2 threads; taper pipe taps are complete turn. On a single start, the lead and the pitch are
chamfered 2-3.5 threads. identical; on a double start, the lead is twice the pitch.
CHAMFER RELIEF MAJOR DIAMETER
The gradual decrease in land height from cutting edge to heel Commonly known as the “outside diameter.” It is the largest
on the chamfered portion, to provide clearance for the cutting diameter of the thread.
action as the tap advances.
MINOR DIAMETER
CREST
Commonly known as the “root diameter.” It is the smallest
The top surface joining the two sides or flanks of the thread; diameter of the thread.
the crest of an external thread is at its major diameter, while the
crest of an internal thread is at its minor diameter. PERCENT OF THREAD
CUTTING FACE One-half the difference between the basic major diameter and
the actual minor diameter of an internal thread, divided by the
The leading side of the land in the direction of cutting rotation on basic thread height, expressed as a percentage.
which the chip forms.
PITCH
FLUTE
The distance from any point on a screw thread to a
The longitudinal channels formed in a tap to create cutting corresponding point on the next thread, measured parallel to
edges on the thread profile, and to provide chip spaces and the axis and on the same side of the axis. The pitch equals one
cutting fluid passages. divided by the number of threads per inch.
HEEL
The edge of the land opposite the cutting edge.
HEIGHT OF THREAD
The distance, measured radially, between the crest and the
base of a thread.
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