9. Comparison of pitch diameter tolerance For Forming Tap Unified Fine Thread (UNF) Intro 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 3B 3BX 2BX 42 SP No.0-80 UNF 2B G3 G5 57 H2 3B 3BX 2BX 47 SL No1-72 UNF 2B G3 G5 63 3BX, Class G, Class H for 3B internal threads H2 2BX, Class G, Class H for 2B internal threads 3B 3BX 2BX 50 internal threads 3B No.2-64 UNF 2B G4 68 PO internal threads 2B H2 H3 3B 3BX 2BX 53 No.3-56 UNF 2B G4 71 ST H2 H3 3B 3BX 2BX 58 No.4-48 UNF 2B G4 G5 78H3H5 ROLL 3B 3BX 2BX 60 No.5-44 UNF 2B G4 G5 80 H3 H5 CARBIDE 3B 3BX 2BX 63 No.6-40 UNF 2B G5 86 H3 H5 LONG 3B 3BX 2BX 67 No.8-36 UNF 2B G5 90 H3 H5 HAND TAPS 3B 3BX 2BX 73 No.10-32 UNF 2B G5 G6 G7 98 H4 H6 EG (STI) 3B 3BX 2BX 77 No.12-28 UNF 2B G6 105 H4 H6 SPECIAL 3B 3BX 2BX 811/4-28 UNF2BG6G7108 THREADS,GAUGES H4 H6 3B 3BX 2BX 90 THREAD 5/16-24 UNF 2B G6 121 MILLS H5 H7 3B 3BX 2BX 933/8-24 UNF2BG7124 DIES H5 H7 3B 3BX 2BX 104 CENTER 7/16-20 UNF 2B G7 137 DRILLS H5 H7 3B 3BX 2BX 106 1/2-20 UNF 2B G7 141 Technical H5 H7 info 661