Steel bar dimensional tolerances and measurement tables are critical parameters that directly affect production efficiency and final part quality. Engineers and procurement professionals often need to compare tolerance values across different EN standards and select the most suitable bar form for their projects.
Tolerance selection has a direct impact on CNC machining costs, material waste, and the precision of the final component. Using a bar with wide tolerances for a high-precision part leads to additional material removal and increased tool wear, while selecting unnecessarily tight tolerances results in higher raw material costs.
In this guide, we present the applicable EN standards for hot-rolled and cold-drawn steel bars, tolerance tables, dimensional ranges based on profile types, and practical recommendations for selecting the right tolerance.
1. EN Standards: Which Standard Covers Which Profile?
Standardized according to European Norms (EN). A separate EN standard applies to each profile form:
| EN Standard | Profile Type | Description | Size Range |
|---|---|---|---|
| EN 10060 | Round | Hot-rolled round steel bar | Ø10–280 mm |
| EN 10059 | Square | Hot-rolled square steel bar | 10×10–200×200 mm |
| EN 10058 | Flat (Strip) | Hot-rolled flat steel bar | 10×6–120×60 mm |
| EN 10061 | Hexagonal | Hot-rolled hexagonal steel bar | AF 14.5–100 mm |
| EN 10278 | All profiles | Cold-drawn (bright) steel bar | Varies depending on profile type |
2. EN 10060: Hot-Rolled Round Steel Tolerances
| Nominal Diameter (mm) | Tolerance (mm) | Ovality Tolerance (mm) |
|---|---|---|
| 10–25 | ±0.4 | 75% of diameter tolerance |
| 25–50 | ±0.4 – ±0.5 | 75% of diameter tolerance |
| 50–100 | ±0.5 – ±0.8 | 75% of diameter tolerance |
| 100–150 | ±0.8 – ±1.0 | 75% of diameter tolerance |
| 150–250 | ±1.0 – ±1.6 | 75% of diameter tolerance |
| 250–280 | ±1.6 – ±2.0 | 75% of diameter tolerance |
Example: A hot-rolled round bar with a nominal diameter of 50 mm may have an actual diameter between 49.5–50.5 mm according to EN 10060. If precision parts will be machined using CNC, sufficient machining allowance should be considered based on this tolerance range.
3. EN 10059: Hot-Rolled Square Steel Tolerances
| Side Length (mm) | Tolerance (mm) | Corner Radius (max) | Out-of-Square Tolerance |
|---|---|---|---|
| 10–25 | ±0.4 | 12% of side length | 75% of side tolerance |
| 25–50 | ±0.4 – ±0.5 | 12% of side length | 75% of side tolerance |
| 50–100 | ±0.5 – ±0.8 | 10% of side length | 75% of side tolerance |
| 100–200 | ±0.8 – ±1.3 | 8% of side length | 75% of side tolerance |
4. EN 10058: Hot-Rolled Flat Steel Tolerances
Flat bars require two-dimensional tolerances: width and thickness. EN 10058 defines separate tolerance values for these two parameters.
Width tolerances:
For widths of 10–50 mm: ±0.5 – ±0.8 mm
For widths of 50–100 mm: ±0.8 – ±1.5 mm
For widths of 100–120 mm: ±1.5 – ±2.0 mm
Thickness tolerances:
For thicknesses of 5–10 mm: ±0.3 – ±0.4 mm
For thicknesses of 10–25 mm: ±0.4 – ±0.5 mm
For thicknesses of 25–60 mm: ±0.5 – ±0.8 mm
The edge profile of flat steel bars is also important. EN 10058 offers both standard (rounded edge) and sharp edge options. For flat bars that will be machined by CNC, choosing sharp edges provides advantages in terms of clamping and alignment.
5. EN 10061: Hot-Rolled Hexagonal Steel Tolerances
Hexagonal bars are toleranced based on the across flats dimension (AF – Across Flats).
| AF Dimension (mm) | Tolerance (mm) | Out-of-Square Tolerance |
|---|---|---|
| 14.5–25 | ±0.3 – ±0.4 | 75% of AF tolerance |
| 25–50 | ±0.4 – ±0.5 | 75% of AF tolerance |
| 50–100 | ±0.5 – ±0.8 | 75% of AF tolerance |
Hexagonal bars are widely used in the production of bolts and nuts, valve bodies, and fastening elements that require wrench engagement. Cold-drawn hexagonal bars offer significantly tighter tolerances (h9–h11) compared to hot-rolled alternatives and are ready for direct machining on CNC automatic lathes.
6. EN 10278: Cold-Drawn (Bright) Steel Tolerances
| Nominal Size (mm) | h9 Tolerance (µm) | h10 Tolerance (µm) | h11 Tolerance (µm) |
|---|---|---|---|
| 6–10 | 0 / –36 | 0 / –58 | 0 / –90 |
| 10–18 | 0 / –43 | 0 / –70 | 0 / –110 |
| 18–30 | 0 / –52 | 0 / –84 | 0 / –130 |
| 30–50 | 0 / –62 | 0 / –100 | 0 / –160 |
| 50–80 | 0 / –74 | 0 / –120 | 0 / –190 |
| 80–120 | 0 / –87 | 0 / –140 | 0 / –220 |
Note: h tolerance classes represent unilateral (negative) deviation: the nominal size is the upper limit, and the actual size is always below the nominal value. For example, a Ø50 mm cold-drawn round bar with h9 tolerance is delivered within the range of 49.938–50.000 mm.
7. Hot-Rolled vs Cold-Drawn: Tolerance Comparison
| Parameter | Hot-Rolled (EN 10060) | Cold-Drawn (EN 10278, h9) |
|---|---|---|
| Tolerance Band | ±0.5 mm (±500 µm) | 0 / –62 µm |
| Total Tolerance Range | 1.0 mm | 0.062 mm |
| Ratio | — | ~16 times more precise |
| Surface Roughness (Ra) | 6.3–12.5 µm | 0.8–3.2 µm |
This comparison clearly demonstrates why cold-drawn bars are preferred in CNC machining. A tolerance that is 16 times more precise means less material removal, shorter machining time, and lower scrap rates.
8. Practical Recommendations for Selecting the Right Tolerance
For CNC machining: use cold-drawn bars with h9 or h11 tolerances. By keeping machining allowance to a minimum, you can reduce processing time and tool wear.
For forging and hot forming: hot-rolled bars with wider tolerances are usually sufficient. Since the material will already be reshaped at high temperature, precise tolerances are generally unnecessary.
For welded structures: hot-rolled bars are typically adequate, as the final dimensions can be achieved through post-weld machining.
For hydraulic piston rods: cold-drawn, ground, and polished bars are required. An h8 tolerance and a surface finish of Ra 0.2–0.4 µm are generally targeted.
For automatic lathes: cold-drawn bars with h11 tolerance are ideal for serial production. They provide the dimensional consistency needed for automatic feeding systems.
For dimensional verification: inspect received bars by taking sample measurements with calipers or micrometers to confirm tolerance compliance. Use the dimensional data in the EN 10204 Type 3.1 certificate as a reference.
8.5. Length Tolerance, Straightness, and Surface Quality
In addition to cross-sectional tolerances, the length tolerance, straightness values, and surface quality of steel bars are also key parameters that directly affect the production process. Standard length tolerances for hot-rolled bars are generally applied as +50 mm / 0 mm (positive deviation). For cold-drawn bars, tighter standard length tolerances such as ±5 mm are commonly offered. From suppliers that provide precision cutting services, cutting tolerances of ±1–2 mm can be requested, which can significantly reduce CNC preparation time.
Straightness (bar bow) is particularly critical in the CNC machining of long parts and in the production of hydraulic piston rods. In hot-rolled bars, straightness values are typically in the range of 3–5 mm/m. In cold-drawn bars, straightness of 0.5–1.0 mm/m can be achieved. In straightened bars, this value can be reduced to below 0.3 mm/m. In hydraulic piston rod applications, the straightness value should not exceed 0.5 mm/m; otherwise, seal life and sealing performance may be negatively affected.
In terms of surface quality, hot-rolled bars have a surface covered with mill scale, and their surface roughness (Ra) is generally in the range of 6.3–12.5 micrometers. In cold-drawn bars, surface roughness decreases to 0.8–3.2 micrometers. In ground and polished bars, values of 0.2–0.4 micrometers can be achieved. For parts that will undergo chrome plating, painting, or other surface treatments, the quality of the base surface directly affects coating adhesion and final appearance.
8.6. Cost Impact of Tolerance Selection
Tolerance selection directly affects the total part cost. Although cold-drawn bars with tighter tolerances have a higher unit price, they generally reduce overall cost by shortening CNC machining time and minimizing material waste. For example, in the production of a 50 mm diameter shaft, using a hot-rolled bar may require approximately 1 mm of material removal, whereas with an h9 tolerance cold-drawn bar, this value decreases to 0.062 mm. This difference can reduce CNC machining time by approximately 40–60%.
Additionally, selecting the appropriate tolerance class helps prevent unnecessary costs caused by purchasing overly precise bars. For instance, choosing an h9 tolerance for a bar used in forging or welded structures does not provide any technical advantage but increases cost. As a general principle, selecting the widest tolerance that meets the final machining requirements and part precision ensures an optimal cost-performance balance.
8.7. Tolerance Verification in the Procurement Process
Performing dimensional verification upon receiving your products is essential for quality assurance. It is recommended to take measurements from the beginning, middle, and end sections of the bar using a caliper or micrometer. For ovality control in round bars, measurements should be taken in two perpendicular directions at the same cross-section.
The EN 10204 Type 3.1 certificate indicates that the supplier has independently verified the dimensional data and is a mandatory document, especially in the automotive, defense, and hydraulic sectors. Ensuring that your supplier maintains stock in different tolerance classes (e.g., EN 10060 standard, EN 10278 h9/h11) and can provide a Type 3.1 certificate offers assurance for production continuity.
8. Future Trends in Automotive Steel
Increasing share of high-strength steels (AHSS): In line with lightweighting goals, 3rd generation AHSS steels (excellent ductility + high strength) will become more widespread.
Special steel requirements for electric vehicles: Steels with high energy absorption capacity will be required for battery enclosures and protective structures.
Demand for green steel: With the European CBAM regulation, low carbon footprint steel supply will become a key selection criterion for OEMs.
Digital traceability: Blockchain-based material traceability systems will increase transparency in the supply chain.
Frequently Asked Questions (FAQ)
What is the difference between h9 and h11 tolerances?
h9 has a tighter (more precise) tolerance range than h11. For example, at a Ø50 mm diameter, h9 tolerance is –62 µm, while h11 tolerance is –160 µm. h9 is more expensive but allows less material removal in CNC machining. The selection depends on the required precision of the final part.
Can hot-rolled bars be machined with CNC?
Yes, hot-rolled bars can be machined with CNC. However, due to their wide tolerances, more material removal is required; the scaled surface accelerates tool wear, and dimensional inconsistencies increase machining time. In serial CNC production, cold-drawn bars generally reduce the total part cost.
Which profiles are covered by the EN 10278 standard?
EN 10278 covers all profiles of cold-drawn (bright) bars: round, square, hexagonal, and flat. It replaces the former DIN standards DIN 668 (round), DIN 670 (square), and DIN 671 (hexagonal).
International Standard Equivalents
Knowing the international equivalents of EN standards is especially important in export projects. The former DIN equivalents are as follows: EN 10060 (round) corresponds to DIN 1013, EN 10059 (square) corresponds to DIN 1014, EN 10058 (flat) corresponds to DIN 1017, and EN 10061 (hexagonal) corresponds to DIN 1015. For cold-drawn steels, EN 10278 replaces the former DIN standards DIN 668 (round), DIN 670 (square), and DIN 671 (hexagonal).
In terms of American standards, ASTM A29/A29M (hot-rolled round and square) and ASTM A108 (cold-drawn) are the main reference standards. Since the ASTM tolerance system differs from EN, both standards may need to be compared in international projects. In Türkiye, the TS EN equivalents of EN standards are valid and published by TSE.
The products in Uyar Çelik’s range—including hot-rolled flat steel (EN 10058), hot-rolled square (EN 10059), hot-rolled round steel (EN 10060), and hot-rolled hexagonal (EN 10061)—are manufactured and delivered in full compliance with these EN standards. Cold-drawn bars are offered in accordance with EN 10278 in h9–h11 tolerance classes.
Conclusion: Steel Bar Dimensions and Tolerance Table
It forms the foundation of correct material procurement and efficient production. EN 10060, EN 10059, EN 10058, EN 10061, and EN 10278 standards define clear tolerance values for hot-rolled and cold-drawn bars.
Selecting the right tolerance prevents unnecessary cost increases and improves production efficiency. In CNC machining applications, the tighter tolerances of cold-drawn bars stand out, while in forging and welding applications, the cost advantage of hot-rolled bars becomes more prominent.
By saving this guide as a reference, you can quickly determine the appropriate standard and tolerance class for your future steel bar orders.
As Uyar Çelik, we maintain a wide stock range of EN-compliant hot-rolled and cold-drawn steel bars (round, square, flat, and hexagonal). For the supply of Type 3.1 certified, dimensionally guaranteed bars: |
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April 2, 2026