Page 9 - Threading_Handbook

Lead Angle
Lead angle is the angle between the helix of thread and a plane of rotation. The lead angle
of the thread depends on the pitch diameter, thread pitch, and the number of thread starts.
This parameter can be represented as a sweep of a right triangle.

The angle of the thread is calculated by the formula given below: INTRODUCTION

(
φL= arctan Lead )
π×Dpitch

Lead= n×P

When:

φL = Lead angle
Dpitch = Pitch diameter (effective diameter of thread)
P = Thread pitch

n = Number of thread starts
π ≈ 3.142

Where the thread is single-start, the lead angle is equal to the helix angle.

Truncation
Truncation is the perpendicular distance to the axis of the thread from the imaginary point
of intersection of two adjacent sides of the thread profile to the nearest point of its top or
bottom.

Truncation
Truncation

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