ASME B18.2.1 Hex Flange Screws Dimensions

Hex flange screws manufactured according to ASME B18.2.1 fastening specifications.

ASME B18.2.1 Hex Flange Screws are commonly used in automotive, machinery, and industrial assembly applications. These flange screws provide improved load distribution, vibration resistance, and secure fastening performance without requiring separate washers.

ASME B18.2.1 Hex Flange Screws Dimensions (mm)

Nominal Size (Ref Inch)

Body Diam., E

Width Across Flats, F

Width Across Corners, G

Maximum Flange Diam., B

Minimum Flange Thickness, K

Maximum Head Height, H

Minimum Hex Height, H₁

Maximum Flange Top Radius, R₂

Minimum Bearing Diam., B₁

Maximum Runout of Bearing Surface FIM

Basic Thread Length, L_T

Maximum Transition Thread Length, Y

Ring T

Ring B

Max.

Min.

Basic (Ref)

Max.

Min.

Max.

Min.

For Screws With L ≤ 152.4mm

For Screws With L > 152.4mm

For Screws With L ≤ 152.4mm

For Screws With L > 152.4mm

Inside Diameter

Thickness

1/4

0.2500

6.350

6.223

9.525

9.322

10.998

10.389

14.224

1.016

7.112

4.318

0.381

12.192

0.254

19.050

25.400

10.160

16.510

10.396

11.125

3.012

5/16

0.3125

7.938

7.785

12.700

12.421

14.656

13.919

17.272

1.270

8.128

5.334

0.483

15.240

0.279

22.225

28.575

10.592

16.942

13.927

14.783

3.701

3/8

0.3750

9.525

9.373

14.288

13.995

16.510

15.697

20.574

1.524

9.906

6.350

0.559

18.542

0.305

25.400

31.750

11.125

17.475

15.705

16.637

4.392

7/16

0.4375

11.113

10.935

15.875

15.545

18.339

17.399

23.622

1.778

11.684

7.620

0.660

21.590

0.330

28.575

34.925

11.786

18.136

17.407

18.542

5.334

1/2

0.5000

12.700

12.522

19.050

18.694

21.996

20.955

27.178

2.032

12.954

8.636

0.762

24.892

0.356

31.750

38.100

12.217

18.567

20.963

22.225

6.022

9/16

0.5625

14.288

14.084

20.638

20.269

23.825

22.733

30.226

2.286

14.478

9.652

0.864

27.940

0.381

34.925

41.275

19.050

22.741

24.130

6.713

5/8

0.6250

15.875

15.672

23.813

23.419

27.508

26.264

33.782

2.540

15.748

10.668

0.965

31.242

0.432

38.100

44.450

19.634

26.271

27.813

7.402

3/4

0.7500

19.050

18.821

28.575

27.940

32.995

31.344

40.386

2.794

18.542

12.954

1.143

37.338

0.508

44.450

50.800

20.320

31.351

33.325

9.035

ASME B18.2.1 Hex Flange Screws Length Tolerance (mm)

Nominal Length

Nominal Size (inches)

1/4 to 3/8

7/16 and 1/2

9/16 to 3/4

7/8 and 1

1 1/8 to 1 1/2

Over 1 1/2

Up to 25.4 mm, incl.

+0.000
0.762

...

Over 25.4 mm to 63.5 mm, incl.

+0.000
1.016

+0.000
1.524

+0.000
2.032

+0.000
2.540

+0.000
3.048

+0.000
4.572

Over 63.5 mm to 101.6 mm, incl.

+0.000
1.524

+0.000
2.032

+0.000
2.540

+0.000
3.556

+0.000
4.064

+0.000
5.080

Over 101.6 mm to 152.4 mm, incl.

+0.000
2.540

+0.000
4.064

+0.000
4.572

+0.000
5.588

Longer than 152.4 mm

+0.000
4.572

+0.000
5.080

+0.000
5.588

+0.000
6.096

Frequently Asked Questions

What grades of nonferrous metal does ASTM F468 cover for flange bolts?

ASTM F468 covers copper (C11000), brass (C26000, C27000, C46200, C46400), bronze (C51000 phosphor, C61300/C61400/C63000 aluminum, C64200, C65100/C65500/C66100 silicon, C67500 manganese), cupro-nickel (C71000, C71500), nickel-base alloys (N04400 Monel 400, N04405, N05500 Monel K-500, N06059 Alloy 59, N06625 Inconel 625, N06686, N10001 Hastelloy B-2, N10276 Hastelloy C-276), aluminum (A92024, A96061, A97075), and titanium (R50250 Gr 1, R50400 Gr 2, R50700 Gr 4, R56400 Gr 5, R56401 Gr 23 ELI, R52400 Gr 7, R58640 Gr 19, R55111 Gr 32) - all available for this product family at TorqBolt.

What is the dimensional standard for these flange bolts?

This product follows ASME B18.2 1, the dimensional standard for flange bolts. Material chemistry, mechanical properties, and acceptance criteria follow ASTM F468 / F468M for nonferrous bolting. TorqBolt supplies both inch-series and metric sizes per the applicable ASME or ISO drawing.

Which F468 grades are best for marine and seawater service?

For seawater bolting per F468: Monel 400 (N04400) and Monel K-500 (N05500) resist chloride stress-corrosion cracking and HF acid; nickel-aluminum bronze C63000 is the standard high-strength marine fastener; cupro-nickel C71500 is preferred for condenser tube-sheet bolting; naval brass C46400 is the lower-cost option for routine marine hardware; titanium Grade 2 (R50400) is the premium choice for severe chloride + chemical service.

Are F468 flange bolts NACE MR0175 acceptable for sour service?

Most F468 nickel and titanium grades are NACE MR0175 / ISO 15156-listed: Monel 400 (N04400), Monel K-500 (N05500) conditional, Inconel 625 (N06625), Hastelloy B-2 (N10001), Hastelloy C-276 (N10276), Alloy 59 (N06059), Alloy 686 (N06686), and all titanium grades (R50400, R52400, R56400, R56401). Aluminum bronzes are generally not preferred for sour service. TorqBolt provides NACE-compliant heat-treat and hardness reports on request.

References & Standards

ASTM F468 / F468M - Standard Specification for Nonferrous Bolts, Hex Cap Screws, and Studs for General Use

ASTM F467 / F467M - Companion specification for Nonferrous Nuts (mate with F468 for matched-alloy assemblies)

ASTM F436 / F436M - Hardened steel washers (ferrous washer companion when nonferrous washers are not specified)

NACE MR0175 / ISO 15156 - Sour-service hardness limits for petroleum and natural gas industries

ASME B18.2.1 / B18.2.3 series / B18.3 / B18.6.7M / B18.31 / B16.5 - Dimensional standards referenced by F468

DIN 912 / 933 / 931 - Metric hex socket head and hex head cap screw dimensional standards

Related Specifications

Surface Treatments

Xylan 1070 / 1014 / 1400 / 1424

Xylar 2 / 101

Geomet 321 / 500 / 720

SermaGard 1105 / 1280

Dacromet 320 / 500

TakeCoat 1000 Ceramic

Delta Tone/Seal

Magnigard

MolyKote

Sherardized

Zinc-Cobalt (ASTM B840)

Zinc-Nickel (ASTM B841)

Certifications

ISO 9001 - 2015 Certified
PED 2014/68/EC
NACE MR0175/ISO 15156-2
NORSOK M-650
DFAR
MERKBLATT AD 2000 W2/W7/W10

ASME B18.2.1 Hex Flange Screws Dimensions