本资料为ANSI B92.1-1970（R1993）版本，详述了SAE花键的标准规范，涵盖尺寸、公差及技术要求等内容。
Form Circle is the circle that defines the deepest points of involute form control for tooth profiles. Together with the tooth tip circle (or start of chamfer circle), it sets the limits on controlling the profile of a tooth. It is located near the major circle on internal splines and close to the minor circle on external splines.
Form Clearance (cF) refers to how far an involute profile extends beyond where it engages with another part, allowing for some looseness between mating parts and accommodating eccentricities between the minor circles of internal splines or major circles of external ones relative to their pitch circles.
The Form Diameter is given as DFe for external splines and DFi for internal splines.
An Internal Spline is a spline formed on the inner surface of a cylinder, while an Involute Spline features teeth with involute profiles.
Lead Variation denotes deviations from intended tooth direction parallel to reference axis, including variations in parallelism and alignment (see Fig. 1a).
Length of Engagement (Lq) measures axial contact length between mating splines.
Machining Tolerance specifies allowable variation in actual space width or tooth thickness.
The Major Circle is the circle formed by the outermost surface of a spline; for external splines, its the outside circle and for internal ones, it’s the root circle. The diameter of this circle is known as Major Diameter (Do for external, Dri for internal).
Minor Circle refers to the innermost surface of a spline. For an external spline, its the root circle while in an internal one, it’s equivalent to the tooth tip circle. Its diameter is called Minor Diameter (Dre for external splines and Di for internal ones).
Nominal Clearance is calculated by subtracting actual tooth thickness of mating parts from space width of an internal spline. It doesnt define fit between components due to variations.
Out-of-roundness measures deviation from true circular shape in a spline.
Parallelism Variation assesses how parallel single teeth are relative to each other (see Fig. 1b).
Pitch is denoted by P/Ps, indicating the ratio of diametral pitch and stub pitch that defines basic radial engagement length above and below the pitch circle for splines.
The Pitch Circle serves as a reference from which all transverse spline dimensions are derived. Its diameter equals the Pitch Diameter (D), while its intersection with tooth profile is known as Pitch Point.
Pressure Angle (φ) represents the angle between an involute tangent line and radial line through point of tangency; standard pressure angles apply unless specified otherwise.
Profile Variation refers to deviations from designed tooth profiles along flanks.
A Spline consists of equally spaced integral keys or keyways around a circle or portion thereof.
Standard Pressure Angle is the designated value at pitch diameter.
Stub Pitch (Ps) denotes radial distance between pitch and major circles for external splines, and minor and pitch circles for internal ones. In this standard, stub pitches are twice diametral pitches.
Total Index Variation indicates greatest difference in spacing of actual tooth profiles compared to perfect positioning among any two teeth.
Total Tolerance combines machining tolerance (m) with variation allowance (λ).
Variation Allowance permits permissible effective variations.
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