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USER GUIDE
Threading Limits with Standard NOTCH-GRIP Inserts
The following charts list the largest pitch that can be applied on internal applications for
Acme and V-Threading NOTCH-GRIP inserts in sizes 2,3, 4 and 6.
60˚ V-Threading Limits Acme Threading Limits
FLT-2 Inserts Internal Threading Limitations FLA-2 Internal Threading Limitations
Minimum Minimum
Threads Nominal Minor Diameter Threads Nominal Minor Diameter
per Inch Thread Size Inch MM per Inch Thread Size Inch MM
6 1-7/8 1.695 43.05 6 2-1/2 2.333 59.26
7 1-3/4 1.595 40.51 8 2-1/4 2.125 53.98
8 1-5/8 1.490 37.85 10 2 1.900 48.26
9 1-9/16 1.442 36.63 12 1-3/4 1.667 42.34
10 1-1/2 1.392 35.36 14 1-5/8 1.554 39.47
11 1-7/16 1.339 34.01 16* 1-1/2 1.438 36.53
12 1-3/8 1.285 32.64 * 16 pitch acme threads and finer can be cut provided the minor
13 1-5/16 1.229 31.22 diameter is 1.438 or larger.
14 1-1/4 1.173 29.79
16 1-1/4 1.182 30.02
18 1-1/8 1.065 27.05
20 1-1/8 1.071 27.20
24 1-1/16 1.017 25.83
* 24 TPI and finer can be cut with a #2 series insert provided that
the minor diameter is 1.000 or larger.

A secondary clearance can be ground
on the leading edge of the form of the
insert to provide sufficient helical clear
ance for machining courser threads and
minor diameter major diameter multiple start threads.
(minimum bore) (nominal thread size)
Modified standard inserts may be produced for
special threads or ones not listed on the charts
shown. Quoted upon request.
FLA-3, 4 & 6 Internal Threading Limitations
threads Minimum
per inch
Threads Nominal Minor Diameter
FLT-3 & 4 Inserts Internal Threading Limitations per Inch Thread Size Inch MM
Minimum 2* 5 4.500 114.30
Threads Nominal Minor Diameter 2-1/2** 4-1/2 4.100 104.14
93.09
3**
3.665
4
per Inch Thread Size Inch MM 4 3-1/2 3.250 82.55
4** 3 2.729 69.32 5 3 2.800 71.12
4-1/2** 2-7/8 2.634 66.90 6 2-1/2 2.333 59.26
5 2-3/4 2.534 64.36 8 2-1/4 2.125 23.98
6 2-1/2 2.320 58.93 10 2 1.900 48.26
7 2-1/4 2.095 53.21 12 1-3/4 1.667 42.34
8 2 1.865 47.37 14 1-5/8 1.554 39.47
9 1-15/16 1.817 46.15 16* 1-1/2 1.438 36.53
10 1-7/8 1.767 44.88 * 16 pitch acme threads and finer can be cut provided the minor
11 1-13/16 1.714 43.54 diameter is 1.438 or larger.
12 1-3/4 1.660 42.16 ** FLA-6 only.
13 1-5/8 1.542 39.17 NOTE: Positive rake ACME inserts are recommended for
14 1-9/16 1.485 37.72 stainless steels and high-temp alloy appl cations.
16* 1-7/16 1.370 34.80 Quoted upon request.
* 16 pitch acme threads and finer can be cut provided the minor
diameter is 1.370 or larger.
** FLT-4 only.
90˚
3˚
back clearance
NOTE: Tool holders are designed to locate the insert at
a 3˚ angle to provide back clearance down the side.

FLTB-2A & 2B Internal Threading Limitations FLTB-3A & 4A Internal Threading Limitations FLTB-3B & 4B Internal Threading Limitations
Nominal Minimum Minimum Minimum
Threads Minor Diameter Threads Nominal Threads Nominal Minor Diameter
per Inch Thread per Inch Thread Size Minor Diameter per Inch Thread Size
Size Inch MM Inch MM Inch MM
8 1-3/4 1.600 40.64 4* 2-1/2 2.200 55.88 4 *2-7/8 2.575 65.41
10 1-5/8 1.505 38.23 5 2-1/4 2.010 51.05 5 2-3/4 2.510 63.75
12 1-1/2 1.400 35.56 6 2 1.800 45.72 6 2-3/8 1.175 29.85
16 1-1/4 1.175 29.85 8 1-3/4 1.600 40.64 8 2-1/8 1.975 50.17
20 1-1/16 1.002 25.45 10 1-7/8 1.755 44.58
10 1-5/8 1.505 38.23
12** 1-1/2 1.400 35.56 12 1-5/8 1.525 38.74
* FLTB-4A insert only 16 1-1/2 1.407 35.74
** 16 or 20 threads per inch can be cut 20 1-7/16 1.378 35.00
providing minor diameter is 1.375 or larger. * FLTB-4B insert only
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