9. Comparison of pitch diameter tolerance
Intro For Forming Tap Unified Coarse Thread (UNC)
Basic Pitch (+) μm
Dia.
0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420

SP 3B 3BX 2BX 47
No.1-64 UNC 2B G3 G5 65
H2

3B 3BX 2BX 53
SL
No.2-56 UNC 2B G4 G5 70 G7
3BX, Class G, Class H for 3B internal threads
H2 H3
2BX, Class G, Class H for 2B internal threads
3B 3BX 2BX 55 internal threads 3B
PO No.3-48 UNC 2B G4 G5 75
internal threads 2B
H2 H3

3B 3BX 2BX 60
ST No.4-40 UNC 2B G4 G5 G6 G7 83
H3 H5

3B 3BX 2BX 63
No.5-40 UNC 2B G4 G5 83
ROLL H3 H5

3B 3BX 2BX 68
No.6-32 UNC 2B G5 G6 G7 93
CARBIDE H3 H5

3B 3BX 2BX 71
No.8-32 UNC 2B G5 G6 G7 G8 96
H3 H5
LONG
3B 3BX 2BX 80
No.10-24 UNC 2B G6 G7 108
H4 H6
HAND,
TAPS 3B 3BX 2BX 82
No.12-24 UNC 2B G6 110
H4 H6
EG (STI)
3B 3BX 2BX 90
1/4-20 UNC 2B G6 G7 123
H4 H6
SPECIAL
THREADS, 3B 3BX 2BX 98
GAUGES 5/16-18 UNC 2B G7 134
H5 H7

THREAD 3B 3BX 2BX 108
MILLS 3/8-16 UNC 2B G8 144
H5 H7

3B 3BX 2BX 116
DIES 7/16-14 UNC 2B G8 154
H5 H7

3B 3BX 2BX 121
CENTER 1/2-13 UNC 2B G9 165
DRILLS H5 H7


Technical
info

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