Tap size

NF/NC UNF/UNC

Threads per inch

Basic major dia (inches)

Basic effective dia (inches)

Basic minor dia of ext. threads (inches)

Basic minor dia of int. threads (inches)

Drill size

0-80

UNF

80

.0600

.0519

.0447

.0465

3/64

1-64

UNC

64

.0730

.0629

.0538

.0561

#54

2-56

UNC

56

.0860

.0744

.0641

.0667

#50

2-64

UNF

64

.0860

.0759

.0668

.0691

#50

4-40

UNC

40

.1120

.0958

.0813

.0849

#43

4-48

UNF

48

.1120

.0985

.0864

.0894

#42

5-40

UNC

40

.1250

.1088

.0943

.0979

#38

5-44

UNF

44

.1250

.1102

.0971

.1004

#37

6-32

UNC

32

.1360

.1177

.0997

.1042

#36

6-40

UNF

40

.1360

.1218

.1073

.1109

#33

8-32

UNC

32

.1640

.1437

.1257

.1302

#29

8-36

UNF

36

.1640

.1460

.1299

.1339

#29

10-24

UNC

24

.1900

.1629

.1389

.1449

#25

10-32

UNF

32

.1900

.1697

.1517

.1562

#21

1/4-20

UNC

20

.2500

.2175

.1887

.1959

#7

1/4-28

UNF

28

.2500

.2268

.2062

.2113

#3

5/16-18

UNC

18

.3125

.2764

.2443

.2524

F

5/16-24

UNF

24

.3125

.2854

.2614

.2674

I

3/8-16

UNC

16

.3750

.3344

.2983

.3073

5/16

3/8-24

UNF

24

.3750

.3479

.3239

.3299

Q

7/16-14

UNC

14

.4375

.3911

.3499

.3602

U

7/16-20

UNF

20

.4375

.4050

.3762

.3834

25/64

1/2-13

UNC

13

.5000

.4500

.4056

.4167

27/64

1/2-20

UNF

20

.5000

.4675

.4387

.4459

29/64

9/16-12

UNC

12

.5625

.5084

.4603

.4723

31/64

9/16-18

UNF

18

.5625

.5264

.4943

.5024

33/64

5/8-11

UNC

11

.6250

.5660

.5135

.5266

17/32

5/8-18

UNF

18

.6250

.5869

.5568

.5649

37/64

3/4-10

UNC

10

.7500

.6650

.6273

.6417

21/32

3/4-16

UNF

16

.7500

.7094

.6733

.6823

11/16

7/8-9

UNC

9

.8750

.8028

.7387

.7547

49/64

7/8-14

UNF

14

.8750

.8286

.7874

.7977

13/16

1-8

UNC

8

1.000

.9188

.8466

.8647

7/8

1-12

UNF

12

1.000

.9459

.8978

.9098

59/64

1 1/8-7

UNC

7

1.1250

1.0322

.9497

.9704

63/64

1 1/8-12

UNF

12

1.1250

1.0709

1.0228

1.0348

1 3/64

1 1/4-7

UNC

7

1.2500

1.1572

1.0747

1.0954

1 7/64

1 3/8-6

UNC

6

1.3750

1.2667

1.1705

1.1946

1 13/64

1 1/2-6

UNC

6

1.5000

1.3917

1.2955

1.3196

1 11/32

1 3/4-5

UNC

5

1.7500

1.6201

1.5046

1.5335

1 35/64

2-4.5

UNC

4 1/2

2.0000

1.8557

1.7274

1.7594

1 25/32