Page 36 - Threading_Handbook

THREAD TURNING The anvil should be selected from the table according to the threading standard. The
correct anvil depends on the right inclination angle (β) and insert size. The inclination angle
(β) is obtained by selecting the thread turning method and finding the helix angle (φ) for
single-start threading, or lead angle (φL) for the multi-start threading. The helix angle (φ)
and the lead angle (φL) are determined as exact values by using the formula below or as a
graph area (see below: Helix (Lead) angle area by using graph, depending on the threading
diameter and lead.

Helix Angle (φ) Calculation by Using Formula Lead Angle (φL) Calculation by Using Formula
Single-Start Threading
Multi-Start Threading
Lead
Lead

(
(
φ=arctan π×Dpitch ) φL=arctan π×Dpitch )

Lead= n×P
When: When:

φ = Helix angle φL = Lead angle
Dpitch = Pitch diameter* Dpitch = Pitch diameter*

* effective diameter of threading * effective diameter of threading

P = Threading pitch P = Threading pitch
π ≈ 3.142 n = Number of threading starts
π ≈ 3.142

Usable Formulas

Lead (inch)= 1 inch ×No. of Starts
TPI
TPI = No. of threading per inch

1 inch = 25.4 mm

Pitch (mm)= 25.4
TPI

36 ISCAR