Machinery's Handbook, 31st Edition
978 Taps Cutter Sweep: The section removed by the milling cutter or the grinding wheel in enter ing or leaving a flute. Cutting Edge: The intersection of cutting edge and the major diameter in the direction of rotation for cutting, which does the actual cutting. Core Diameter: The diameter of a circle that is tangent to the bottom of the flutes at a given point on the axis. Dryseal: A thread system used for both external and internal pipe threads applications designed for use where the assembled product must withstand high fluid or gas pressure without the use of sealing compound. Eccentric: Not having a common center. Eccentricity: One half of the total indicator variation (TIV) with respect to the tool axis. Entry Taper: The portion of the thread forming, where the thread forming is tapered toward the front to allow entry into the hole to be tapped. External Center: The pointed end on a tap. On bottom-chamfered taps, the point on the front end may be removed. Flank: The flank of a thread is the surface connecting the crest with the root. Flank Angle: Angle between the individual flank and the perpendicular to the axis of the thread, measured in an axial plane. A flank angle of a symmetrical thread is commonly termed the “half angle of thread.” Flank, Leading: 1) Flank of a thread facing toward the chamfered end of a threading tool; and 2) The leading flank of a thread is the one which, when the thread is about to be assembled with a mating thread, faces the mating thread. Diameter, Major: The major cylinder on a straight thread. Diameter, Minor: The minor cylinder on a straight thread. Flank, Trailing: The trailing flank of a thread is the one opposite the leading flank. Flutes: Longitudinal channels formed in a tap to create cutting edges on the thread pro file and to provide chip spaces and cutting fluid passages. On a parallel or straight-thread tap, they may be straight, angular or helical; on a taper-thread tap, they may be straight, angular or spiral. Flute Lead Angle: Angle at which a helical- or spiral-cutting edge at a given point makes with an axial plane through the same point. Flute, Spiral: A flute with uniform axial lead in a spiral path around the axis of a coni cal tap. Flute, Straight: A flute that forms a cutting edge lying in an axial plane. Flute, Tapered: A flute lying in a plane intersecting the tool axis at an angle. Full Indicator Movement (FIM): The total movement of an indicator where appropri ately applied to a surface to measure its surface. Functional Size: The functional diameter of an external or internal thread is the PD of the enveloping thread of perfect pitch, lead, and flank angles, having full depth of engagement but clear at crests and roots, and of a specified length of engagement. Heel: Edge of the land opposite the cutting edge. Height of Thread: The height of a thread is the distance, measured radially, between the major and minor cylinders or cones, respectively. Holes, Blind: A hole that does not pass through the work piece and is not threaded to its full depth. Holes, Bottom: A blind hole that is threaded close to the bottom. Hook Angle: Inclination of a concave cutting face, usually specified either as Chordal Hook or Tangential Hook. Hook, Chordal Angle: Angle between the chord passing through the root and crest of a thread form at the cutting face, and a radial line through the crest at the cutting edge. Hook, Tangential Angle: Angle between a line tangent to a hook cutting face at the cut ting edge and a radial line to the same point. Internal Center: A countersink with clearance at the bottom, in one or both ends of a tool, which establishes the tool axis.
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