Hexagonal bar stock

Hexagonal bar stock supplies six longitudinal flats so that a component can retain a wrenching or locating feature without milling the entire polygon from round stock. “Hexagonal” describes the section, not its alloy, strength or dimensional quality. For example, Nucor lists cold-finished steel hexagons in several carbon and alloy grades, while Wieland supplies a drawn precision brass hexagon as W5006. These products require different material and delivery specifications. Nucor cold-finished bar, Wieland W5006, pp. 2–3

Dimensions and usable envelope

An ideal sharp-corner 20 mm across-flats hexagon needs a 23.094 mm circular envelope, using 20 / cos(30°). A nominal 20 mm round blank is too small to contain it. For a feeder or finished part, check actual across-corners size, corner profile, twist and straightness.

The width across flats, AF, is the perpendicular distance between two opposite faces. The width across corners, AC, is the distance between opposite vertices. Keep these names on drawings and purchase orders: a round opening that admits the AF dimension does not necessarily admit the corners. Wieland's W5006 dimensional and condition tables explicitly use width across flats. W5006, pp. 2–3

For an ideal regular hexagon with across-flats dimension s, elementary geometry gives:

These are geometric calculations, not acceptance tolerances. Actual corner radii, imperfect flatness, size variation and end preparation must come from the ordered product requirements. Do not infer a maximum corner envelope or a guaranteed machined diameter solely from nominal AF. A supplier's designation “sharp-edged,” such as Wieland's EN 12164 description, still needs interpretation through the applicable delivery specification. W5006, p. 2

Material, process and specification

Specify alloy or grade and supplied condition alongside the shape. ASTM A108-24 covers cold-finished carbon and alloy steel bars for mechanical applications; its scope includes straight lengths and coils. It is not a specification for every metal sold as hexagonal bar, and supplementary requirements apply only when individually ordered. Its stated standard units are inch-pound, with SI conversions informational. ASTM A108-24 scope

Nucor's published cold-finished hexagon offering spans 5/16–4 inches depending on grade. The overall range is not evidence that every listed grade is available at every size. The producer also explains that cold-finished tolerances depend on carbon content, shape and finishing method; “cold finished” should not be converted into an assumed universal AF tolerance. Confirm the grade-size combination, condition and agreed dimensional table with the supplying mill. Nucor product and tolerance information

For European orders, identify both the standard number and edition. The current DIN record is DIN EN 10278:2024-01, adopting EN 10278:2023, whose title specifically concerns dimensions and tolerances of bright steel products of stainless and other special steels. Check that scope against the material being ordered rather than copying an undated “EN 10278” note from an older drawing. Brass may instead refer to copper-alloy delivery standards, as the W5006 example does. DIN edition and scope, W5006

Separate size, straightness and condition

A bar can have acceptable AF size yet be unsuitable for a long feeder or a part that retains several aligned wrench flats. Evaluate cross-section size, longitudinal straightness, twist, surface condition and cut-end condition separately. Length and end preparation also affect the usable blank: a nominal stock length is not automatically a finished component length. Nucor offers different end preparations, while Wieland publishes feeder-oriented end geometry for its precision product. Nucor, W5006, p. 2

As a bounded example, W5006 states maximum straightness of 1 mm/m for 10–30 mm AF rods. Its R430 condition at over 10–35 mm AF lists minimum tensile strength 430 MPa and minimum 0.2% proof strength 220 MPa; the harder R500 row applies to 4–10 mm AF and lists 500 and 350 MPa respectively. Those are product- and size-specific entries, not properties of arbitrary brass hexagons. The brochure also carries a disclaimer that its characteristics are not guaranteed; establish contractual requirements in the order. W5006, pp. 2–4

Worked geometry example

Illustrative calculation, assuming a perfectly regular, sharp-cornered 20.000 mm AF section:

• Across corners = 2 × 20 / √3 = 23.094 mm.
• Area = (√3 / 2) × 20² = 346.410 mm².
• A 1,000 mm length has volume 346,410 mm³, or 0.346410 L.

A nominal 20 mm round blank cannot contain that hexagon: its diameter is smaller than the 23.094 mm corner envelope. Conversely, an ideal 20 mm diameter circle fits inside the hexagon. Turning that circle would remove 346.410 − π × 10² = 32.251 mm² of section, about 9.31% of the original area, before end losses or other features. These results do not include cleanup allowance, bar tolerances or deflection. Select actual blank size from the finished drawing and the supplier's limits; calculate mass using the specified alloy's density rather than a generic “hex bar” density.

Selection and inspection

Treat the following as procurement and process decisions, not additional mill guarantees:

1. Define the retained geometry. State AF, tolerances, required corners, flat orientation, straightness and twist where they affect the finished component.
2. Define the material evidence. Order grade, condition, applicable product standard and required certification. Geometry alone establishes neither pressure rating nor fastener strength.
3. Check the machine envelope. Use the corner envelope for feeder passages, tooling clearance and rotating stock assessment; qualify the actual collet or chuck contact on the supplied section.
4. Allow for processing. Include end cropping, facing and cleanup allowance. Where substantial asymmetric machining is planned, assess dimensional movement on representative stock rather than treating a straight incoming bar as a stability guarantee.
5. Inspect against the order. Measure multiple flats and locations as appropriate; distinguish a local size result from longitudinal straightness or twist. Resolve which supplied surfaces may remain on the finished part.

Source versions and related reference

Reviewed 2026-11-01, America/Los_Angeles. ASTM identifies A108-24; DIN identifies the national January 2024 adoption of EN 10278:2023. Wieland W5006 prints 01/2022 on its final page; the web search publication timestamp is not its technical edition. Nucor's live product page provides no explicit technical revision date. Verify current availability and purchase requirements directly when ordering. ASTM, DIN, W5006

Stock forms and dimensions