Involute Splines 2335 Tooth Proportions.— There are 17 pitches: 2.5 ∕ 5, 3 ∕ 6, 4 ∕ 8, 5 ∕ 10, 6 ∕ 12, 8 ∕ 16, 10 ∕ 20, 12 ∕ 24, 16 ∕ 32, 20 ∕ 40, 24 ∕ 48, 32 ∕ 64, 40 ∕ 80, 48 ∕ 96, 64 ∕ 128, 80 ∕ 160, and 128 ∕ 256. The numerator in this fractional designation is known as the diametral pitch and controls the pitch diam- eter; the denominator, which is always double the numerator, is known as the stub pitch and controls the tooth depth. For convenience in calculation, only the numerator is used in the formulas given and is designated as P . Diametral pitch, as in gears, means the number of teeth per inch of pitch diameter. Table 1 shows the symbols and Table 2 the formulas for basic tooth dimensions of invo lute spline teeth of various pitches. Basic dimensions are given in Table 3. Table 1. American National Standard Involute Spline Symbols ANSI B92.1-1996 c v effective clearance M i measurement between pins, internal spline c F form clearance N number of teeth D pitch diameter P diametral pitch D b base diameter P s stub pitch D ci pin contact diameter, internal spline P/P s spline pitch D ce pin contact diameter, external spline p circular pitch D Fe form diameter, external spline r f fillet radius D Fi form diameter, internal spline s actual space width, circular D i minor diameter, internal spline s v effective space width, circular D o major diameter, external spline t actual tooth thickness, circular D re minor diameter, external spline (root) t v effective tooth thickness, circular D ri major diameter, internal spline (root) λ variation allowance d e diameter of measuring pin for external spline ε involute roll angle d i diameter of measuring pin for internal spline φ pressure angle K e change factor for external spline φ D standard pressure angle K i change factor for internal spline φ ci pressure angle at pin contact diameter, internal spline L spline length φ ce pressure angle at pin contact diameter, external spline L a active spline length φ i pressure angle at pin center, internal spline L g length of engagement φ e pressure angle at pin center, external spline m machining tolerance φ F pressure angle at form diameter M e measurement over pins, external spline Machinery's Handbook, 31st Edition
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