UNC Thread ANSI B1.1

UNC - Unified Coarse Thread. The old definition NC - National Coarse is comparable with the metric thread. The new term UNC is comparable with the ISO metric thread. NC and UNC threads are interchangeable, in an similar manner to the metric and the ISO metric thread.

Nominal

Major

Major

Tapping

TPI

Pitch

Diameter

Diameter

Diameter

Drill Size

mm

 

Inch

mm

mm

 

1 - 64 UNC

0.073

1.854

1.50

64

0.397

2 - 56 UNC

0.086

2.184

1.80

56

0.453

3 - 48 UNC

0.099

2.515

2.10

48

0.529

4 - 40 UNC

0.112

2.845

2.35

40

0.635

5 - 40 UNC

0.125

3.175

2.65

40

0.635

6 - 32 UNC

0.138

3.505

2.85

32

0.794

8 - 32 UNC

0.164

4.166

3.50

32

0.794

10 - 24 UNC

0.190

4.826

4.00

24

1.058

12 - 24 UNC

0.216

5.486

4.65

24

1.058

1/4" - 20 UNC

0.250

6.350

5.35

20

1.270

5/16" - 18 UNC

0.313

7.938

6.80

18

1.411

3/8" - 16 UNC

0.375

9.525

8.25

16

1.587

7/16" - 14 UNC

0.438

11.112

9.65

14

1.814

1/2" - 13 UNC

0.500

12.700

11.15

13

1.954

9/16" - 12 UNC

0.563

14.288

12.60

12

2.117

5/8" - 11 UNC

0.625

15.875

14.05

11

2.309

3/4" - 10 UNC

0.750

19.050

17.00

10

2.540

7/8" - 9 UNC

0.875

22.225

20.00

9

2.822

1" - 8 UNC

1.000

25.400

22.85

8

3.175

1 1/8" - 7 UNC

1.125

28.575

25.65

7

3.628

1 1/4" - 7 UNC

1.250

31.750

28.85

7

3.628

1 3/8" - 6 UNC

1.375

34.925

31.55

6

4.233

1 1/2" - 6 UNC

1.500

38.100

34.70

6

4.233

1 3/4" - 5 UNC

1.750

44.450

40.40

5

5.080

2" - 4 1/2 UNC

2.000

50.800

46.30

4.5

5.644

2 1/4" - 4 1/2 UNC

2.250

57.150

52.65

4.5

5.644

2 1/2" - 4 UNC

2.500

63.500

58.50

4

6.350

2 3/4" - 4 UNC

2.750

69.850

64.75

4

6.350

3" - 4 UNC

3.000

63.500

71.10

4

6.350

3 1/4" - 4 UNC

3.250

82.550

77.45

4

6.350

3 1/2" - 4 UNC

3.500

88.900

83.80

4

6.350

3 3/4" - 4 UNC

3.750

95.250

90.15

4

6.350

4" - 4 UNC

4.000

101.600

96.50

4

6.350