Ordering cold drawn steel sounds simple until you have to specify the right size. Too small and the part will not fit; too large and you waste money on machining time and material. This guide covers the standard size ranges for cold drawn round bars, square bars, flat bars and hexagonal bars, along with tolerance standards and practical tips for buyers.
Cold drawn steel is priced per ton, but it is machined by the millimeter. A bar that is 0.5 mm out of tolerance means extra turning time, more tool wear and a higher scrap rate. Unlike hot rolled bar, where buyers accept a few millimeters of variation, cold drawn bar is expected to arrive ready for machining. Getting the size range and tolerance right on your RFQ saves weeks of back-and-forth with the supplier.
Round bar is the most widely used cold drawn section. Our production range covers:
| Category | Diameter Range | Typical Tolerance |
|---|---|---|
| Small precision bars | Ø5 mm – Ø20 mm | h9 (±0.015–0.025 mm) |
| General purpose | Ø20 mm – Ø50 mm | h9 (±0.025–0.039 mm) |
| Large bars | Ø50 mm – Ø100 mm | h11 (±0.08–0.14 mm) |
Common stock diameters include Ø8, Ø10, Ø12, Ø16, Ø20, Ø25, Ø30, Ø40, Ø50, Ø60, Ø80 and Ø100 mm. For CNC automatic lathes, smaller bars under Ø20 mm are usually supplied in coil or straight lengths.
Square bar is used for shafts, connectors and structural components where a flat surface is needed.
| Category | Size Range (A×A) | Typical Tolerance |
|---|---|---|
| Small squares | 4×4 mm – 20×20 mm | h9 |
| Standard squares | 20×20 mm – 50×50 mm | h9/h11 |
| Large squares | 50×50 mm – 120×120 mm | h11 |
Most buyers order 10×10, 20×20, 25×25, 30×30, 40×40 and 50×50 mm. Sizes above 80×80 mm are usually produced to order.
Flat bar is specified by width and thickness. It is widely used in elevator guide rails, machinery frames and welding structures.
| Parameter | Range |
|---|---|
| Width | 20 mm – 200 mm |
| Thickness | 3 mm – 40 mm |
| Common stock widths | 20, 30, 40, 50, 60, 80, 100, 120, 150 mm |
| Common stock thicknesses | 3, 5, 6, 8, 10, 12, 15, 20, 25 mm |
The width-to-thickness ratio matters. A 100×5 mm flat bar is much easier to produce than a 50×30 mm bar. If your required section is unusual, send us a drawing for feasibility confirmation.
Hexagonal bar is measured across flats (AF). It is the standard shape for nuts, bolts and wrench-driven components.
| Category | Across Flats (S) | Notes |
|---|---|---|
| Small hex | S6 – S19 | Metric and imperial (3/8" – 3/4") |
| Standard hex | S19 – S50 | Most commonly ordered range |
| Large hex | S50 – S100 | Produced to order |
We stock common sizes S8, S10, S17, S19, S24, S30, S36 and S41. Imperial sizes (1/2", 5/8", 3/4", 1", 1-1/4") are available for export to the US and Southeast Asia.
European buyers usually reference EN 10278, which specifies two tolerance classes for cold drawn steel:
h9: Tighter tolerance, used for precision machined parts and automatic lathe work.
h11: Standard tolerance, suitable for structural and general engineering applications.
Our default production tolerance is h9/h11 per EN 10278. If your drawing specifies a tighter tolerance (h8 or better), let us know on your RFQ and we will confirm feasibility.
Standard cold drawn bar lengths are 2,000–6,000 mm. We also cut to your exact requirement from 50 mm up to 6,000 mm with ±0.5 mm tolerance. Straightness is ≤0.5 mm/m, which is suitable for automatic feeding into CNC machines.
A complete RFQ should include:
Section shape: round, square, flat, hexagonal or custom profile
Dimensions: diameter / width×thickness / across flats
Material grade: Q235, C45, 40Cr, 42CrMo4 or other
Tolerance class: h9, h11 or per your drawing
Length: random length, fixed length or cut-to-size
Quantity: weight in tons or pieces
For more on what to include in your RFQ, read our cold drawn steel tolerances and RFQ guide.
Suzhou Zhenfu Cold-Drawn Steel Co., Ltd. produces cold drawn round, square, flat, hexagonal and custom special-shaped profiles with over 18 years of experience. All sizes listed above are available from stock or production, with EN 10204 3.1 mill test certificate.
Send us your size list or drawing, and we will confirm availability, price and delivery within 24 hours.
Experience the outstanding industrial quality of Zhenfu. Our meticulously designed cold-drawn steel can enhance performance in various fields. If you need a customized solution, please contact us and collaborate with Zhenfu.
