Cold Drawn Hexagonal Steel Bar – Sizes, Grades and Tolerances

We draw hexagon steel bar from S5 up to S100 (across-flats) on our 8-ton to 120-ton cold drawing lines. Hex bar is the standard blank for nuts, bolts, shafts and machined fasteners, and the cold drawn process gives you a clean, scale-free surface with consistent across-flats dimensions. Most buyers order it because it cuts out a machining pass compared to round bar turned down to hex.

Available sizes and grades

What buyers use it for

Hex bar goes mainly into fasteners, nuts and bolts, drive shafts, machine tool parts, and agricultural machinery components. If your drawing specifies a hex blank that will be machined into a part, ordering the cold drawn bar at the finished across-flats size usually means one fewer machining operation and less material loss.

What to specify when you ask for a quote

Send us the across-flats size, the grade, and the quantity in tons. If the part is machined from hex, also tell us the finished size and tolerance so we can confirm whether the drawn bar already meets it. Standard sizes ship from stock in 3–7 working days; special grades like 38Cr2 or 12Cr1MoV run 15–35 days depending on heat availability.

Request a quote: send us your hex bar size, grade and quantity via the contact form, or check our cold drawn steel size guide for reference. We reply with price and lead time within one working day.

Related pages: Cold Drawn Flat Steel · Cold Drawn Square Steel · How Cold Drawn Steel Is Made · About Our Factory

Common Across-Flats Series

The across-flats dimension – the distance between two opposite flat faces – is the size that defines hex bar. Standard metric series run S5, S6, S8, S10, S12, S14, S17, S19, S22, S24, S27, S30, S32, S36, S41, S46, S50, S55, S60, S65, S70, S75, S80, S85, S90, S95 and S100. Our stock concentrates on S8 to S30, the sizes that feed fastener and machine-part production. S17 and S19 are worth calling out separately: they match the hex heads of M10 and M12 bolts, so nut and bolt makers draw their blank stock at exactly these sizes.

Metric and Imperial Hex Sizes

Imperial hex is specified in inches and maps directly to wrench sizes. Common dimensions are 1/4" (6.35 mm), 5/16" (7.94 mm), 3/8" (9.53 mm), 7/16" (11.11 mm), 1/2" (12.70 mm), 9/16" (14.29 mm), 5/8" (15.88 mm), 3/4" (19.05 mm), 7/8" (22.23 mm) and 1" (25.40 mm). If your print is in inches, send the inch size and we confirm the metric equivalent before quoting – the drawing tolerance applies to the metric dimension, so we make that explicit in the quotation.

What Tolerance Means on Hex Bar

Across-flats is the controlled dimension on drawn hex bar, held to h9–h13 per GB/T 905, with tighter ranges on request. For S17, h11 holds the across-flats to about ±0.11 mm. The corner-to-corner (across-corners) dimension is derived from the across-flats and is controlled by the die geometry, but it is not a primary tolerance dimension – specify it on the drawing only if the part truly depends on the corners. Straightness is held to the drawn-bar standard and is verified on the roller straightener before cutting.

Grades and What They Mean in Practice

Q235 is the general structural grade for nuts, spacers and parts that are machined or welded without high load. 35# and 45# are medium-carbon grades with more strength, used for shafts and fasteners that take real load. 40Cr and 42CrMo are alloy grades for components hardened after machining – gears, pins, high-stress fasteners. 65Mn is a spring steel for elastic parts. S45C is the JIS counterpart of 45#. 1.0715 (9SMnPb28) is a leaded free-cutting grade that machines very fast on automatic lathes. 38Cr2, 12Cr1MoV and 15CrMo are low-alloy grades for boiler, pressure and elevated-temperature service. If your drawing names a grade not listed, send it – we confirm heat availability before quoting.

Drawn Hex vs Machined Hex

Two ways to get hex stock: draw it, or turn round bar down to hex. Drawing forms the section in one pass – no chips, no machining time, a bright scale-free surface, and consistent across-flats from end to end. Turning round bar to hex removes material on every piece and costs more on long or high-volume orders. The drawn bar also keeps a work-hardened surface, which helps on parts that see wear. When your annual volume is beyond a few tonnes, drawn hex is normally the cheaper and more consistent route.

Stainless and Alloy Options

Beyond carbon steel we draw hex in SUS304 and SUS316 on request, for corrosion-resistant fasteners and fittings. Alloy grades such as 38Cr2, 12Cr1MoV and 15CrMo are drawn to order against heat availability. Stainless drawing needs different lubrication and die design than carbon steel, so confirm the grade and quantity with us before ordering – the lead time and minimum quantity are both grade-dependent.

Delivery Condition and Packing

Hex bar is delivered cold drawn (BK) as standard, or annealed (SR) where the buyer machines deep profiles or needs a softer blank. Bars are straightened, cut to length and deburred. For sea freight we bundle with steel strapping and oil the surface on request. Standard carbon grades ship from stock in 3–7 working days; special and alloy grades run 15–35 days depending on heat availability.

Send us the across-flats size, grade and quantity in tons for a quote, and tell us the finished part size if the bar is machined – we confirm whether the drawn size already meets it. We also draw round bar, square bar and flat steel on the same lines.

Where Hexagonal Steel Bar Is Specified

Fastener and nut blanks. Drawn hex bar is the blank stock for hex nuts, bolt heads and captive fasteners. The across-flats dimension (S) is the finished hex size, so a 17 mm S bar becomes a 17 mm A/F nut with only a facing cut. Common blanks are S=17, 19, 22, 24 and 30 mm in Q235 and C45; hardened fastener grades use 40Cr with post-machining heat treatment.

Torque transmission. A hexagonal shaft transmits torque through its flat faces – the shape stops the shaft from spinning in its mating socket without a key. Drawn hex shaft in C45 or 40Cr is used for drive spindles, worm shafts and manual actuator rods, where the hex section is the drive interface itself.

Tool handles, keys and locating pins. Hex bar makes square-wrench-compatible handles, locking keys and locating pins that need to be held or turned with a standard wrench. The sharp, consistent corners are the working surfaces here, which is exactly what rolling cannot guarantee.

Locking and adjustment parts. Hex spacers, threaded studs and adjustable feet use drawn hex bar because the flat faces give a reliable grip for a spanner during adjustment. Sizes below S=14 mm are drawn as stock; larger sections to S=65 mm are drawn to order.

Inspection and Certificates

Across-flats dimension, corner condition, straightness and surface are checked on the drawing line. Orders carry an EN 10204 3.1 mill certificate on request, and third-party inspection is arranged for fastener-grade deliveries.