Page 82 - TURNING CATALOG p635-848

THREADING USER GUIDE

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 Lead angle (φL) calculation by using the

the Single-Start Threading Formula Single-Start Threading Formula

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

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