logo9 MARYLAND METRICS -- THREAD IDENTIFICATION CHART SECTION (A):
FOR MAJOR DIAMETERS FROM 0.25 mm TO 7.723 mm
(Also see the IMPORTANT notes at the bottom of this table.)

BASIC MAJOR DIAMETER NOMINAL DIAMETER: METRIC STD. REF. METRIC -- PITCH in mm NOMINAL DIAMETER: AMERICAN AMERICAN -- PITCH in THREADS per Inch UNIFIED MINI-ATURE BRITISH ASSOC-IATION NOMINAL DIAM-ETER BRITISH -- PITCH in THREADS per Inch
Inch mm mm . COARSE FINE . UNC UNF UNEF UNM BA No. BRITISH BA BSW BSF BSPT
0.0098 0.25 . . 0.07 . . . . . . 25 . 363 . . .
0.0114 0.29 . . 0.08 . . . . . . 24 . 317 . . .
0.0118 0.30 0.3 D 0.075 . . . . . . . . . . . .
0.0118 0.30 0.3 I 0.08 . 0.30 mm . . 318 0.30 . . . . . .
0.0130 0.33 . . 0.09 . . . . . . 23 . 282 . . .
0.0138 0.35 0.35 II 0.09 . 0.35 mm . . 282 0.35 . . . . . .
0.0146 0.37 . . 0.098 . . . . . . 22 . 254 . . .
0.0157 0.40 0.4 I D 0.1 . 0.40 mm . . 254 0.40 . . . . . .
0.0165 0.42 . . 0.11 . . . . . . 21 . 230.91 . . .
0.0177 0.45 0.45 II 0.1 . 0.45 mm . . 254 0.45 . . . . . .
0.0189 0.48 . . 0.12 . . . . . . 20 . 211.67 . . .
0.0197 0.50 0.5 I D 0.125 . 0.50 mm . . 203 0.50 . . . . . .
0.0209 0.53 . . . . 0 . 160 . . . . . . . .
0.0213 0.54 . . 0.14 . . . . . . 19 . 181.43 . . .
0.0217 0.55 0.55 II 0.125 . 0.55 mm . . 203 0.55 . . . . . .
0.0236 0.60 0.6 I D 0.15 . 0.60 mm . . 169 0.60 . . . . . .
0.0244 0.62 . . 0.15 . . . . . . 18 . 169.33 . . .
0.0276 0.70 0.7 II D 0.175 . 0.70 mm . . 145 0.70 17 . 149.41 . . .
0.0311 0.79 . . 0.19 . . . . . . 16 . 133.68 . . .
0.0315 0.80 0.8 I D 0.2 . 0.80 mm . . 127 0.80 . . . . . .
0.0340 0.86 . . . . 0 . 120 . . . . . . . .
0.0354 0.90 0.9 II D 0.225 . 0.90 mm . . 113 0.90 15 . 120.95 . . .
0.0394 1 1 I D 0.25 0.2 1.00 mm . . 102 1.00 14 . 110.44 . . .
0.0433 1.1 1.1 II 0.25 0.2 1.10 mm . . 102 1.10 . . . . . .
0.0470 1.19 . . . . 0 . 90 . . . . . . . .
0.0472 1.2 1.2 I D 0.25 0.2 1.20 mm . . 102 1.20 13 . 101.6 . . .
0.0512 1.3 . . 0.28 . . . . . . 12 . 90.71 . . .
0.0551 1.4 1.4 II D 0.3 0.2 1.40 mm . . 85 1.40 . . . . . .
0.0591 1.5 1.5 . 0.31 . . . . . . 11 . 81.93 . . .
0.0600 1.524 . . . . #0 . 80 . . . . . . . .
0.0625 1.59 . . . . . . . . . . 1/16 . 60 . .
0.0629 1.6 1.6 I 0.35 0.2 . . . . . . . . . . .
0.0669 1.7 1.7 D 0.35 0.2,0.25 . . . . . 10 . 72.57 . . .
0.0709 1.8 1.8 II 0.35 0.2,(0.4) . . . . . . . . . . .
0.0730 1.854 . . . . #1 64 72 . . . . . . . .
0.0748 1.9 . . 0.39 . . . . . . 9 . 65.13 . . .
0.0781 1.98 . . . . . . . . . . 5/64 . 56 . .
0.0787 2 2 I D 0.4 0.25,0.3 . . . . . . . . . . .
0.0860 2.184 . . . . #2 56 64 . . . . . . . .
0.0866 2.2 2.2 II 0.45 0.25 . . . . . 8 . 59.07 . . .
0.0906 2.3 2.3 D 0.4 0.25,0.35 . . . . . . . . . . .
0.0937 2.38 . . . . . . . . . . 3/32 . 48 . .
0.0984 2.5 2.5 I 0.45 0.35 . . . . . 7 . 52.92 . . .
0.0990 2.515 . . . . #3 48 56 . . . . . . . .
0.1024 2.6 2.6 D 0.45 0.25,0.35 . . . . . . . . . . .
0.1094 2.78 . . . . . . . . . . 7/64 . 48 . .
0.1102 2.8 . . 0.53 . . . . . . 6 . 47.93 . . .
0.1120 2.845 . . . . #4 40 48 . . . . . . . .
0.1181 3 3 I D 0.5 0.35,(0.6) . . . . . . . . . . .
0.1250 3.175 . . . . #5 40 44 . . . 1/8 . 40 . .
0.1260 3.2 . . 0.59 . . . . . . 5 . 43.05 . . .
0.1380 3.5 3.5 II D 0.6 0.35,0.5 #6 32 40 . . . . . . . .
0.1417 3.6 . . 0.66 . . . . . . 4 . 38.49 . . .
0.1563 3.969 . . . . . . . . . . 5/32 . 32 . .
0.1575 4 4 I D 0.7 0.5,(0.75) . . . . . . . . . . .
0.1614 4.1 . . 0.73 . . . . . . 3 . 34.8 . . .
0.1640 4.166 . . . . #8 32 36 . . . . . . . .
0.1772 4.5 4.5 II 0.75 0.5 . . . . . . . . . . .
0.1850 4.7 . . 0.81 . . . . . . 2 . 31.36 . . .
0.1875 4.762 . . . . . . . . . . 3/16 . 24 32 .
0.1900 4.826 . . . . #10 24 32 . . . . . . . .
0.1969 5 5 I D 0.8 0.5,0.75,(0.9) . . . . . . . . . . .
0.2087 5.3 . . 0.9 . . . . . . 1 . 28.22 . . .
0.2160 5.486 . . . . #12 24 28 32 . . . . . . .
0.2165 5.5 5.5 III 0.9 0.5 . . . . . . . . . . .
0.2188 5.556 . . . . . . . . . . 7/32 . 24 28 .
0.2362 6 6 I D 1 0.5,0.75 . . . . . 0 . 25.4 . . .
0.2480 6.3 6.3 GM 1 . . . . . . . 1/8 . . . 28(H)
0.2500 6.35 . . . . 1/4 20 28 32 . . 1/4 . 20 26 .
0.2756 7 7 III D 1 0.5,0.75 . . . . . . . . . . .
0.2812 7.144 . . . . . . . . . . 9/32 . 20 26 .
0.3041 7.723 . . . . . . . . . . 1/16 . . . 28
  • The British thread system is fractionally based, but all thread vee angles are different than the American fractionally or decimally based threads. Most thread per inch values are different than in the American System.
  • Taper pipe thread major diameters are measured at the gauge point.
  • (H)= BSPT copper pipe thread.
  • Dimensions within ( ) in the M FINE column are obsolete French or Japanese threads.
  • Dimensions within ( ) in the BSW column are obsolete British coarse threads.
  • The 6.3 mm dimension; marked GM is an obsolete General Motors thread.
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