ASME B18.6.7M Hex Head Machine Screws (Metric)
Metric hex head machine screws per ASME B18.6.7M — head dimension table M2 to M12 with pitches: body diameter DS, width across flats Sa, across corners Ea, head height K, underhead fillet Da/R, plus the non-ISO M10 15 mm across-flats variant defined in the source footnotes.
Last updated: 2026-11
Specifications
B18.6.7M is the metric machine-screw counterpart of the small hex bolt: a screw sized for tapped holes and thin sections, threaded to the head, with the hex giving real torque on a part too small for a comfortable bolt. The collected table runs M2 x 0.4 to M12 x 1.75 and the numbers read small where it matters: across flats Sa of 3.2 mm at M2, 5 at M3, 8 at M5, 13 at M8, 16 at M10, 18 at M12 — small wrenches, shallow heads (K max 1.6 at M2 rising to 9 at M12), and a three-row header that separates body diameter DS (max = nominal; min 1.65 at M2, 10.68 at M12) from the hex geometry. Two details on this page have real buying consequences. First, the underhead fillet columns (transition diameter Da max and radius R min, 0.1 at M2 rising) — on a machine screw driven into a tapped hole, the fillet is what resists snapping at the head. Second, the source's footnote b, carried verbatim in the table: M10 screws exist in two head widths, 15 mm and 16 mm across flats, and the 15 mm variant "is not ISO Standard" — unless 15 mm is specifically ordered, 16 mm is furnished, and the table tabulates both rows (M10 x 1.5 at 16 and M10 x 1.5b at 15). Strength classes and finish are not tabulated — per RFQ.
| Standard | ASME B18.6.7M — metric hex head machine screws, M2 x 0.4 through M12 x 1.75, threaded to the head |
|---|---|
| Width across flats Sa | Max/min (M2: 3.2/3.02; M3: 5/4.82; M5: 8/7.78; M8: 13/12.73; M10: 16/15.73; M12: 18/17.73), plus the M10 x 1.5b variant at 15/14.73 |
| M10 fork (footnote b) | M10 heads come in 15 mm and 16 mm across flats; the 15 mm head is not ISO standard and is furnished only when specifically ordered — both rows tabulated (M10 x 1.5 and M10 x 1.5b) |
| Head height K | Max/min per size (M2: 1.6/1.3; M5: 3.8/3.3; M8: 6/5.2; M10: 7.5/6.5; M12: 9/7.8), across corners Ea min (M2: 3.38; M12: 19.86; the 15 mm M10 variant Ea 16.5) |
| Body diameter DS | Max = nominal, min for rolling (M2: 1.65; M5: 4.36; M10: 8.86; M12: 10.68) |
| Underhead fillet | Transition diameter Da max and radius R min per size (R 0.1 at M2 rising through the ladder) — the head-to-shank stress path |
| Not tabulated | Strength classes, thread lengths, finish — per RFQ |
| Nominal Size and Thread Pitch | DS | DS | Sa | Sa | Ea | K | K | DA | R |
|---|---|---|---|---|---|---|---|---|---|
| Nominal Size and Thread Pitch | Body Diameter | Body Diameter | Hex Width Across Flats | Hex Width Across Flats | Hex Width Across Corners | Head Height | Head Height | Underhead Fillet | Underhead Fillet |
| Nominal Size and Thread Pitch | Body Diameter | Body Diameter | Hex Width Across Flats | Hex Width Across Flats | Hex Width Across Corners | Head Height | Head Height | Transition Dia | Radius |
| Nominal Size and Thread Pitch | Max | Min | Max | Min | Min | Max | Min | Max | Min |
| ASME B18.6.7M - M2 × 0.4 | 2 | 1.65 | 3.2 | 3.02 | 3.38 | 1.6 | 1.3 | 2.6 | 0.1 |
| ASME B18.6.7M - M2.5 × 0.45 | 2.5 | 2.12 | 4 | 3.82 | 4.28 | 2.1 | 1.8 | 3.1 | 0.1 |
| ASME B18.6.7M - M3 × 0.5 | 3 | 2.58 | 5 | 4.82 | 5.4 | 2.3 | 2 | 3.6 | 0.1 |
| ASME B18.6.7M - M3.5 × 0.6 | 3.5 | 3 | 5.5 | 5.32 | 5.96 | 2.6 | 2.3 | 4.1 | 0.1 |
| ASME B18.6.7M - M4 × 0.7 | 4 | 3.43 | 7 | 6.78 | 7.59 | 3 | 2.6 | 4.7 | 0.2 |
| ASME B18.6.7M - M5 × 0.8 | 5 | 4.36 | 8 | 7.78 | 8.71 | 3.8 | 3.3 | 5.7 | 0.2 |
| ASME B18.6.7M - M6 × 1 | 6 | 5.21 | 10 | 9.78 | 10.95 | 4.7 | 4.1 | 6.8 | 0.3 |
| ASME B18.6.7M - M8 × 1.25 | 8 | 7.04 | 13 | 12.73 | 14.26 | 6 | 5.2 | 9.2 | 0.4 |
| ASME B18.6.7M - M10 × 1.5 | 10 | 8.86 | 16 | 15.73 | 17.62 | 7.5 | 6.5 | 11.2 | 0.4 |
| ASME B18.6.7M - M12 × 1.75 | 12 | 10.68 | 18 | 17.73 | 19.86 | 9 | 7.8 | 13.2 | 0.4 |
| ASME B18.6.7M - M10 × 1.5b | 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. | 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. | 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. | 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. | 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. | 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. | 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. | 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. | 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. | 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. |
- Three-row header carried as three label cells; trailing row repeats footnotes a/b in every column, carried verbatim — footnote b defines the M10 15 mm vs 16 mm across-flats fork.
Materials
- Metric hex machine screws ship in carbon steel by property class (4.8/8.8 typical for small sizes) and stainless A2/A4; small hex heads strip or round at the corners first, so torque limits matter more than class at M2-M5. State size, pitch and material on the RFQ — pitch is part of the designation on this family
Ordering & documentation
Documents
Shipments are backed by Mill Test Certificate (MTC), Dimensional Report, Salt Spray Test Report on request, with full batch traceability from raw material to finished product. Quality management follows the owner-confirmed compliance list: ISO 9001:2015, RoHS, REACH. Exact document sets are confirmed on the order.
Quotation
- The fastener family (ASME B18.6.7M Hex Head Machine Screws (Metric)) plus the standard designation from your drawing — DIN / ISO / JIS / ASTM / ANSI, or a drawing for custom parts.
- Size (diameter and length), thread type (metric or inch), property class or grade, and coating or finish.
- Quantity per size and your target delivery date.
- Destination country, and any required documents (for example a mill test certificate) so the quote includes them.
Sample & supply
Minimum order quantity is 10,000 pieces. Stock items run 3–7 days. Quantities or variants outside the standard range are confirmed at quotation.
Storage & shipping
Parts are packed for export and shipped factory-direct to buyers in Europe, Asia, the Americas and the Middle East. Store fasteners dry and protected until installation, and keep coated parts in their packaging until use; specific packing and preservation requirements can be stated on the order and confirmed at quotation.
Frequently asked questions
There are two M10 rows in the table — which M10 machine screw do I get?
By default, the 16 mm head. The collected table tabulates both rows and its footnote b states the rule verbatim: M10 screws with 15 mm width across flats are not ISO standard, and unless the 15 mm head is specifically ordered, the 16 mm head is furnished. The 15 mm variant exists to mate with existing ISO hex hardware patterns where M10 shares the 15 mm wrench of some flange series — but a drawing that simply says "M10 hex machine screw" means 16 mm here. The rows are labeled as printed (M10 x 1.5 and M10 x 1.5b) and carried in the rendered table below; if your assembly was qualified around the 15 mm head, write "M10 x 1.5, 15 mm across flats" on the RFQ explicitly — the whole point of the footnote is that silence delivers the other size.
Machine screw or small hex bolt — where is the line at M6-M12?
On thread run and application, not head shape. Both carry the same hex geometry family — the collected table's across-flats ladder (10 at M6, 13 at M8, 16 at M10, 18 at M12) overlaps the small hex bolt sizes — but a B18.6.7M machine screw is threaded to the head and sized for engagement in a tapped hole or thin nut, while a hex bolt expects a through hole with a nut on the far side and offers defined thread-length bands. The buying consequences: a machine screw's length is essentially all thread (state grip carefully on thin sections), and its head height and fillet are proportioned for torque on small parts rather than high preload. Where the drawing names either designation, order it — a bolt threaded-to-head is not automatically a machine screw in tolerance terms, and assemblies qualified on one geometry should not quietly receive the other.
Related knowledge
- Thread-Forming vs Thread-Cutting vs Thread-Rolling Self-Tapping Screws: What the Evidence Settles on Base Material
- Screw Family Selection by Base Material: Wood, Machine and Self-Tapping Threads, Engagement and Coating
- Hex Bolts vs Socket Head Cap Screws: What the Evidence Settles on Strength, Clearance and Cost
Request a Quote
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What to include in your inquiry
- ✓ Standard and property class (e.g. DIN 912, ISO 4762, class 8.8) — or a drawing for custom parts.
- ✓ Sizes, lengths and thread type (metric or inch).
- ✓ Quantity per size and your target delivery date.
- ✓ Destination country, plus any coating or finish requirement.
- ✓ Any documents you need with the shipment (e.g. mill test certificate) so the quote includes them.
- ✓ Your inquiry goes straight to the factory team by email and gets a reply within 24 hours.
- ✓ Factory-direct pricing
- ✓ Standard and custom specifications
- ✓ Factory-direct export to buyers in Europe, Asia, the Americas and the Middle East
- ✓ Full fastener family support