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Threads For Self-Tapping Screws Type B                           ANSI B18.6.4

Nominal Size

Threads per Inch

Major Dia.

Minor Dia.

Point Dia

Point Taper Length

Minimum Practical screw Length

Max

Min

Max

Min

Max

Min

Max

Min

90 Heads

Csk Heads

6

20

.139

.132

.104

.099

.095

.089

.100

.075

1/4

9/32

7

19

.154

.147

.115

.109

.105

.099

.105

.079

1/4

5/16

8

18

.166

.159

.122

.116

.112

.106

.111

.083

9/32

11/32

10

16

.189

.182

.141

.135

.130

.123

.125

.094

5/16

3/8

12

14

.215

.208

.164

.157

.152

.145

.143

.107

11/32

7/16

14

14

.246

.237

.192

.185

.179

.171

.143

.107

3/8

1/2

 

Suggest Test Plate Thickness & Hole Sizes for Types AB, B, 25

Nominal Size

Thickness

Hole Size

Gage

Max

Min

Drill Size

Hole Dia.

2-32

18

.0500

.0460

48

.0760

3-28

18

.0500

.0460

46

.0810

4-24

18

.0500

.0460

44

.0860

5-20

18

.0500

.0460

36

.1065

6-20

14

.0770

.0730

32

.1160

7-19

14

.0770

.0730

30

.1285

8-18

14

.1270

.1230

29

.1360

10-16

1/8

.1270

.1230

21

.1590

12-14

1/8

.1270

.1230

3/16

.1875

-14

3/16

.1905

.1845

5.5mm

.2165

5/16-12

3/16

.1905

.1845

I

.2720

3/8-12

3/16

.1905

.1845

21/64

.3281