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Technical Information
TopThread ™
American Buttress (7° Pressure Flank Leading) NTB-A Inserts • Push Type
Insert vs. Toolholder Orientation
chuck
chuck
external
anti-clockwise
rotation
anti-clockwise
rotation
7º
NTB-2RA
NTB-3RA
NTB-4RA
feed
7° pressure fl ank
of the thread being
the leading fl ank
NTB-2LA
NTB-3LA
NTB-4LA
7º
7° pressure fl ank
of the thread being
the leading fl ank
external buttress
7° pressure fl ank leading
seating
surface
in bar
seating
surface
in toolholder
insert
notch
feed
NTB-2RA
NTB-3RA
NTB-4RA
internal
insert
notch
NTB-2LA
NTB-3LA
NTB-4LA
internal buttress
7° pressure fl ank leading
Reference Dimensions
Infeed Angle vs. Chip Load: 7° Pressure Flank Leading
“A” reference
.010" infeed
.010" infeed
nose radius
.0052"
chip load
.0039"
chip load
D maximum
depth with “A”
style insert
.007" chip load
.0012"
chip load
0º infeed angle
15º infeed angle
feed direction
insert D
(inch) “A” ref.
(inch) nose radius
(inch) pitch based on
maximum radius
NTB-2A
NTB-3A
NTB-4A .133
.171
.218 .024
.031
.049 .002–.004
.005–.008
.008–.012 16–20 TPI
8–16 TPI
4–6 TPI
feed direction
NTB-A insert
NOTE: For balanced chip load, 15° infeed angle is suggested.
Internal Threading Limitations
internal threading limitations
NTB-3 and NTB-4A Buttress threading inserts
TPI nominal
thread size minimum minor
diameter
(inch) TPI nominal
thread size minimum minor
diameter
(inch)
8 1-3/4 1.600 10 1-5/8 1.505 12 1-1/2 1.400 16 1-1/4 1.175 20 1-1/16 1.002 4*
5
6
8
10
12** 2-1/2
2-1/4
2
1-3/4
1-5/8
1-1/2 2.200
2.010
1.800
1.600
1.505
1.400
*NTB-4A insert only.
**Can cut 16 or 20 threads per inch provided minor diameter is 1.375" or larger.
Threads per Inch vs. Maximum Root Radius Chart (Inch)
TPI
maximum root radius
20
16
12
10
8
6
5
4
3
2-1/2
2
1-1/2 1-1/4
1
.0036 .0045 .0059 .0071 .0089 .0119 .0143 .0179 .0238 .0268 .0375 .0476 .0572 .0714
NOTE: Special Buttress forms are available upon request.
widia.com
F95
internal threading limitations
NTB-2A Buttress threading inserts