粗牙、中等级外螺纹的公差和极限尺寸                                               in

(a)公称直径小于和等于3/4in

公称直径

牙数

大   径

中  径

小   径

不镀或镀前

镀后

不镀或镀前

镀后

不镀或镀前

镀后

max

公差

min

max

max

公差

min

max

max

公差

min

max

1/8

40

0.1238

0.0045

0.1193

0.1250

0.1078

0.0029

0.1049

0.1090

0.0918

0.0061

0.0857

0.0930

3/16

24

0.1863

0.0055

0.1808

0.1870

0.1596

0.0035

0.1561

0.1608

0.1329

0.0076

0.1253

0.1341

1/4

20

0.2488

0.0061

0.2427

0.2500

0.2168

0.0039

0.2129

0.2180

0.1848

0.0084

0.1764

0.1860

5/16

18

0.3112

0.0066

0.3046

0.3125

0.2756

0.0042

0.2714

0.2769

0.2400

0.0089

0.2311

0.2413

3/8

16

0.3736

0.0070

0.3666

0.3750

0.3336

0.0045

0.3291

0.3350

0.2936

0.0095

0.2841

0.2950

7/16

14

0.4360

0.0075

0.4285

0.4375

0.3903

0.0048

0.3855

0.3918

0.3446

0.0101

0.3345

0.3461

1/2

12

0.4985

0.0081

0.4904

0.5000

0.4451

0.0052

0.4399

0.4466

0.3917

0.0110

0.3807

0.3932

9/16

12

0.5609

0.0082

0.5527

0.5625

0.5075

0.0053

0.5022

0.5071

0.4541

0.0111

0.4430

0.4557

5/8

11

0.6233

0.0086

0.6147

0.6250

0.5651

0.0056

0.5595

0.5668

0.5069

0.0116

0.4953

0.5086

11/16

11

0.6858

0.0088

0.6770

0.6875

0.6276

0.0058

0.6218

0.6293

0.5694

0.0118

0.5576

0.5711

3/4

10

0.7482

0.0092

0.7390

0.7500

0.6842

0.0060

0.6782

0.6860

0.6202

0.0123

0.6079

0.6220

(b)公称直径大于3/4in

公称

直径

牙数

大   径

中   径

小   径

max

公差

min

max

公差

min

max

公差

min

7/8

9

0.8750

0.0097

0.8653

0.8039

0.0064

0.7975

0.7328

0.0131

0.7197

1

8

1.0000

0.0103

0.9897

0.9200

0.0068

0.9132

0.8400

0.0139

0.8261

1¹/₈

7

1.1250

0.0110

1.1140

1.0035

0.0072

1.0263

0.9420

0.0148

0.9272

1¹/₄

7

1.2500

0.0112

1.2388

1.1585

0.0074

1.1511

1.0670

0.0150

1.0520

1¹/₂

6

1.5000

0.0121

1.4879

1.3933

0.0080

1.3853

1.2866

0.0162

1.2704

1³/₄

5

1.7500

0.0131

1.7369

1.6219

0.0086

1.6133

1.4938

0.0175

1.4763

2

4.5

2.0000

0.0138

1.9862

1.8577

0.0091

1.8486

1.7154

0.0185

1.6969

2¹/₄

4

2.2500

0.0146

2.2354

2.0899

0.0096

2.0803

1.9298

0.0196

1.9102

2¹/₂

4

2.5000

0.0150

2.4850

2.3399

0.0100

2.3299

2.1798

0.0200

2.1598

2³/₄

3.5

2.7500

0.0157

2.7343

2.5670

0.0104

2.5566

2.3840

0.0211

2.3629

3

3.5

3.0000

0.0161

2.9839

2.8170

0.0108

2.8062

2.6340

0.0215

2.6125

3¹/₄

3.25

3.2500

0.0167

3.2333

3.0530

0.0111

3.0419

2.8560

0.0222

2.8338

3¹/₂

3.25

3.5000

0.0170

3.4830

3.3030

0.0114

3.2916

3.1060

0.0225

3.0835

3³/₄

3

3.7500

0.0176

3.7324

3.5366

0.0118

3.5247

3.3232

0.0234

3.2998

4

3

4.0000

0.0178

3.9822

3.7866

0.0121

3.7745

3.5732

0.0236

3.5496

4¹/₂

2.875

4.5000

0.0185

4.4815

4.2773

0.0126

4.2647

4.0546

0.0244

4.0302

5

2.75

5.0000

0.0192

4.9808

4.7672

0.0131

4.7541

4.5344

0.0252

4.5092

5

2.625

5.5000

0.0198

5.4802

5.2561

0.0137

5.2424

5.0122

0.0260

4.9862

6

2.5

6.0000

0.0205

5.9795

5.7439

0.0141

5.7298

5.4878

0.0268

5.4610