Threading Solutions - Vargus

3.
Tangential Line Approach
This method is very simple, and has all of the advantages of the tangential arc method. However, it is applicable
only with external threads.
External Thread
2
3
1
4
D2
Threading Tool
D1
Workpiece
1-2: radial entry with simultaneous feed along z axis
2-3: helical movement during one full orbit (360º)
3-4: radial exit
Preparing for the Thread Milling Operation
1.
Calculation of Rotational Velocity and Feed at the Cutting Edge
N =
12 x V
þ x D 2
V = N x þ x D 2
12
F 1 = N x z x f
N - Rotational Velocity [R.P.M.]
V - Cutting Speed [ft/min]
D 2 - Toolholder Cutting Dia. [inch]
F 1 - Tool Feed Rate at the Cutting Egde [inch/min]
z - No. of Cutting Edges
f - Feed per Tooth per Rotation [inch/rev]
N
D 2
Vc
TM Technical Data
2.
Calculation of Feed Rates at the Tool Center Line
ØDo
Thread
F2=
F1=
ØD 2
F 1
F 2
Internal Thread
F1 X (Do - D2)
Do
F2 X Do
Do - D2
Threading
Tool
F1 X (Di + D2)
F2=
Di
F2 X Di
F1=
Di + D2
ØD 2
Threading
Tool
F 1 ØDi
Thread
F 2
External Thread
On most CNC machines, the
feed rate required for
programming is that of the
center-line of the tool. When
dealing with linear tool
movement, the feed rate at
the cutting edge and the
center line are identical, but
with circular tool movement
such is not the case.
The equations define the
relationship between feed
rates at the cutting edge and
at the tool center line.
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