UNF
screw threads to 1 inch in diameter

Index to fastener thread series

The Unified National Fine series are the inch-based thread series currently used in the United States, and have been since 1949.¹ They superceded the American National Series (NF).

Pink shading = obsolete sizes that might be found on old equipment but aren't used on new.

Nut size is the distamce across flats.

See this table for diameters of twist drills.

Gage
and
Fractional
Sizes
Major diam.
(inches)
Clear-
ance
drill
tpi Tap drill
Nut Size
0 0.0600 #52 80 364 532
1 0.0730 #48 72 #53 532
2 0.0860 #43 64 #50 316
3 0.0990 #37 56 #45 316
4 0.1120 #32 48 #42 ¼″
5 0.1250 #30 44 #37 ¼″
6 0.1380 #27 40 #33 516
8 0.1640 #18 36 #29 1132
10 0.190 #9 32 #21 38
12 0.216 #2 28   716
¼″ 0.2500 F 28 #3 716
516 0.3125 P 24 I 916
38 0.375 W 24 Q 58
0.390 0.390 25/64  
716 0.4375 29⁄64 20 2564  
½″ 0.5000  33/64″ 20 2964 ¾″
916 0.5625 916 18 3364  
58 0.6250 58 18 3764  
¾″ 0.7500 ¾ 16   1¹⁄8
78 0.8750 78 14   1516
1″ 1.0000 1″ 12   1½″

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