
Major Diameter
The largest diameter of a screw thread
Pitch Diameter
On a straight thread, the diameter of an
imaginary cylinder, the surface of which cuts the
thread forms where the width of the thread and
groove are equal
Minor Diameter
The smallest diameter of a screw thread
For a straight thread, where the lead of the thread
and the pitch diameter circle circumference form
a right angled triangle, the helix angle is the angle
opposite of the lead
A thread formed on a cylinder
A thread formed on a cone
Technical
information
for
Threading
Technical
information
for
Threading
Special
Features
Thread
Turning
Method
>
External
Thread
External
Thread
Drawing
No
.
Thread
Inserts
&
Tool
holder
Rotation
Feed
Direction
Helix
Method
A
thread
on
the
external
surface
of
a
cylinder
screw
or
cone
Counter
clockwise
EX
RH
Towards
chuck
Regular
Right
Hand
External
H
EX
LH
Clockwise
From
chuck
Reversed
H
Counter
clockwise
IN
RH
Towards
chuck
Regular
Major
0
Pitch
0
Minor
©
<
-
Right
Hand
Internal
Q
<
IN
LH
Clockwise
From
chuck
Reversed
<
Counter
clockwise
EX
LH
Towards
chuck
Regular
Depth
of
Thread
-
-
>
Left
Hand
External
m
EX
RH
Clockwise
From
chuck
Reversed
The
distance
between
the
crest
and
root
measured
from
normal
to
the
axis
Counter
clockwise
IN
LH
Towards
chuck
Regular
PitchJ
7
Thread
>
Angle
i
Helix
.
f
Angle
Left
Hand
Internal
IN
RH
Clockwise
From
chuck
Reversed
Pitch
Root
Helix
Angle
!
Crest
The
distance
between
the
corresponding
points
on
adjacent
thread
forms
measured
parallel
to
the
axis
.
This
distance
can
be
defined
in
millimeters
or
by
the
tpi
(
threads
per
inch
)
,
which
is
the
reciprocal
of
the
pitch
External
LH
Thread
External
RH
Thread
-
Straight
Thread
Nominal
Diameter
The
diameter
of
which
the
diameter
limits
are
derived
by
the
application
of
deviation
allowances
and
tolerances
Internal
Thread
A
thread
on
the
internal
surface
of
a
cylinder
or
cone
Taper
Thread
Right
handed
thread
The
Helix
Angle
(
j
)
Left
handed
thread
Internal
LH
Thread
Internal
RH
Thread
Lead
(
L
)
Helix
angle
(
i
)
|
X
Pitch
diamiter
(
D
)
A
thread
which
,
when
viewed
axially
,
winds
in
a
counter
clockwise
and
receding
direction
.
All
left
handed
threads
are
designated
LH
A
thread
which
,
when
viewed
axially
,
winds
in
a
clockwise
and
receding
direction
Threads
are
always
right
handed
unless
they
are
specified
For
a
straight
thread
,
where
the
lead
of
the
thread
and
the
pitch
diameter
circle
circumference
form
a
right
angled
triangle
,
the
helix
angle
is
the
angle
opposite
of
the
lead
Calculating
the
Helix
Angle
(
J
3
)
A
thread
in
which
the
lead
is
an
integral
multiple
,
greater
than
one
,
of
the
pitch
.
A
multi
start
thread
permits
a
more
rapid
advance
without
a
coarser
(
larger
)
thread
form
Machining
a
Multi
-
start
Thread
Helix
Angle
Diagram
Pitch
P
*
Pitch
P
*
Third
Start
Machined
(
Final
,
3
Starts
Thread
)
First
Start
Machined
Second
Start
Machined
[
tpi
]
0
5
j
4
s
3
]
j
=
2
H
=
m
P
Feed
towards
the
chuck
7
/
2.25
/
/
Special
_
y
Toolholders
7
2.5
/
Standard
/
?
helix
angle
/
/
D
3
/
/
3.5
7
7
/
/
4
/
7
7
\
4.5
oL
H
1
Shim
i
angle
1
1.5
i
7
Pitch
5
7
7
/
Pitch
Pitch
Lead
Standard
toolholder
pocket
angle
6
7
7
9
7
7
1
Insert
Profile
Style
24
•
The
helix
angle
is
calculated
by
the
following
formula
:
Pitch
diameter
[
mm
]
150
—
i
=
0
E
50
100
200
Feed
towards
the
tailstock
24
Partial
Profile
Full
Profile
Full
Profile
for
Fine
Pitches
Semi
Full
\
\
11
PXN
9
-
1
P
=
tan
\
7
Reversed
helix
angle
JIX
D
6
/
\
5
\
\
4.5
E
-
1
\
CO
4
\
\
H
1
1.5
°
\
3.5
3
-
Helix
angle
(
)
°
P
-
Pitch
(
mm
)
N
-
No
.
of
starts
D
-
Pitch
diameter
(
mm
)
Lead
=
P
x
N
Shim
angle
Standard
toolholder
pocker
angle
\
3
\
The
V
partial
profile
insert
cuts
without
The
full
profile
insert
will
form
a
topping
the
outer
diameter
of
the
thread
.
The
same
insert
can
be
used
for
a
range
of
different
thread
pitches
standard
,
a
separate
insert
is
which
have
a
common
thread
angle
required
The
full
profile
for
Fine
Pitches
will
complete
thread
profile
including
the
form
a
complete
thread
crest
.
For
every
thread
pitch
and
The
Semi
profile
insert
will
form
a
complete
thread
including
crest
The
topping
of
the
outer
diameter
is
radius
but
without
topping
the
outer
diameter
Mainly
used
for
trapezoidal
profiles
Special
Toolholders
2.5
The
dimension
H
1
(
cutting
edge
height
)
remains
^
constant
with
every
insert
/
shim
combination
=
-
2
H
generated
by
second
tooth
=
-
m
•
The
helix
angle
can
also
be
found
from
the
diagram
below
*
For
Multi
-
start
threads
,
use
the
lead
value
instead
of
the
pitch