Sandvik Coromant Threading - Manual (Page 28)

28
 P
d2 x π
=
P
d
2

=
=
=
A.
B.
tan
 




6 mm
40 mm x π


6 mm
40 mm x π
 = arctan
 = arctan
2. Applications – Thread turning
Methods for selecting the correct shim
Pitch
Effective diameter of thread
For a pitch of 6 mm and a workpiece diameter of 40 mm, a 3° shim is
required. For a pitch of 5 threads per inch and a diameter of 4 inches, a
1° shim is required.
Workpiece diameter and pitch infl uence inclination angles
Workpiece mm
inch
diameter
Lead (Pitch) mm Threads/inch
Two alternative ways to select the correct shim:
A. Use the diagram, selecting shims.
B. Use the formula to calculate the helix angle to choose the corresponding shim.
P = 6 mm
d
2
= 40 mm
= 2.7°
use a 3° shim
= .91°
use a 1° shim
1
5 t.p.i.
4” x π
P = 5 t.p.i.
d
2
= 4”