What is a Metric Hex-Head Machine Screws in Inconel 718 per ASTM A1014?

Metric Hex-Head Machine Screws per ASME B18.6.7M dimensional standard, manufactured in UNS N07718 (Inconel 718 / Alloy 718) precipitation-hardening nickel-chromium superalloy per ASTM A1014 / A1014M for high-temperature bolting service to about 705 °C (1300 °F). Tensile strength ≥185 ksi (1275 MPa), 0.2% yield ≥150 ksi (1035 MPa), hardness 331–444 HBW after solution + double-age treatment.

What heat treatment is required for Metric Hex-Head Machine Screws in ASTM A1014?

ASTM A1014 §5.2 mandates solution treatment at 1725–1850 °F (940–1010 °C) ±25 °F with air cool or faster, followed by precipitation aging at 1325 °F (720 °C) for 8 hours minimum, furnace cool to 1150 °F (620 °C) at 100 °F/hour, hold 8 hours, air cool. Total precipitation aging cycle minimum 18 hours. Straightening permitted only between solution and aging — never after aging.

Why use Inconel 718 for Metric Hex-Head Machine Screws versus stainless or low-alloy steel?

Inconel 718 (Metric Hex-Head Machine Screws) retains its 185 ksi tensile to 705 °C where 4140 (B7), 410SS (B6), and 304/316SS lose 60-80% of room-temperature strength. Stress-rupture rating: 23 h minimum at 1200 °F / 100 ksi per ASTM A1014. Used in gas-turbine engines, liquid-oxygen turbo-pumps, downhole H₂S service, and oxy-fuel petrochemical reactors where ASTM A193 grades cannot meet service temperature.

Metric Machine Screws Inconel 718

ASME B18.6.7M Metric Machine Screws – Dimensions, Specifications & Standards

Metric Machine Screws for Precision Mechanical & Electronic Assemblies.

ASME B18.6.7M Metric Machine Screws are metric-series small fasteners designed to thread into pre-tapped holes or pair with metric nuts, widely used in electronics, instrument panels, control equipment, and appliance manufacturing where compact and lightweight fastening is required. The standard governs metric dimensions for head styles (pan, flat, oval, binding, etc.), head diameter, head height, slot or recess dimensions, body diameter, thread pitch, and thread length. In corrosion-sensitive applications, these screws are manufactured per ASTM A1014/A1014M for UNS N07718 (Inconel 718) bolting, delivering fine dimensional precision and outstanding resistance to corrosion, stress cracking, and high-temperature degradation for aerospace, oil & gas instrumentation, and chemical process applications. Stainless steel grades (ASTM F593) and nonferrous alloys (ASTM F468) are also commonly used. B18.6.7M ensures precise interchangeability across all metric machine screw sizes and head configurations.

ASME B18.6.7M Metric Machine Screws Dimensions

Nominal Size and Thread Pitch	DS	S^a	Ea	K	DA	R
M2 × 0.4	2	1.65	3.2	3.02	3.38	1.6	1.3	2.6	0.1
M2.5 × 0.45	2.5	2.12	4	3.82	4.28	2.1	1.8	3.1	0.1
M3 × 0.5	3	2.58	5	4.82	5.4	2.3	2	3.6	0.1
M3.5 × 0.6	3.5	3	5.5	5.32	5.96	2.6	2.3	4.1	0.1
M4 × 0.7	4	3.43	7	6.78	7.59	3	2.6	4.7	0.2
M5 × 0.8	5	4.36	8	7.78	8.71	3.8	3.3	5.7	0.2
M6 × 1	6	5.21	10	9.78	10.95	4.7	4.1	6.8	0.3
M8 × 1.25	8	7.04	13	12.73	14.26	6	5.2	9.2	0.4
M10 × 1.5	10	8.86	16	15.73	17.62	7.5	6.5	11.2	0.4
M12 × 1.75	12	10.68	18	17.73	19.86	9	7.8	13.2	0.4
M10 × 1.5^b	10	8.86	15	14.73	16.5	7.5	6.5	11.2	0.4
a Dimensions across flats and across corners of the head are measured at the point of maximum metal. Taper of sides of head (angle between one side and the axis) shall not exceed 2° or 0.10 mm, whichever is greater, the specified width across flats being the large dimension. b The M10 size screws having heads with 15 mm width across flats are not ISO Standard. Unless M10 size screws with 15 mm width across flats are specifically ordered, M10 size screws with 16 mm width across flats shall be furnished.

Nominal Size and Thread Pitch

S^a

Body Diameter

Hex Width Across Flats

Hex Width Across Corners

Head Height

Underhead Fillet

Transition Dia

Radius

Max

Min

Max

Min

Max

Min

Max

Min

M2 × 0.4

1.65

3.2

3.02

3.38

1.6

1.3

2.6

0.1

M2.5 × 0.45

2.5

2.12

3.82

4.28

2.1

1.8

3.1

0.1

M3 × 0.5

2.58

4.82

5.4

2.3

3.6

0.1

M3.5 × 0.6

3.5

5.5

5.32

5.96

2.6

2.3

4.1

0.1

M4 × 0.7

3.43

6.78

7.59

2.6

4.7

0.2

M5 × 0.8

4.36

7.78

8.71

3.8

3.3

5.7

0.2

M6 × 1

5.21

9.78

10.95

4.7

4.1

6.8

0.3

M8 × 1.25

7.04

12.73

14.26

5.2

9.2

0.4

M10 × 1.5

8.86

15.73

17.62

7.5

6.5

11.2

0.4

M12 × 1.75

10.68

17.73

19.86

7.8

13.2

0.4

M10 × 1.5^b

8.86

14.73

16.5

7.5

6.5

11.2

0.4

a Dimensions across flats and across corners of the head are measured at the point of maximum metal. Taper of sides of head (angle between one side and the axis) shall not exceed 2° or 0.10 mm, whichever is greater, the specified width across flats being the large dimension.
b The M10 size screws having heads with 15 mm width across flats are not ISO Standard. Unless M10 size screws with 15 mm width across flats are specifically ordered, M10 size screws with 16 mm width across flats shall be furnished.

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 B18.6.7M Metric Machine Screws – Dimensions, Specifications & Standards

ASME B18.6.7M Metric Machine Screws Dimensions

Related Specifications

Surface Treatments

Certifications

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