How to Specify Cold Drawn Steel Bar Tolerance, Straightness and Cut Length

1. Name the Governing Product Standard

The same nominal size can be ordered under different product standards, customer drawings or internal specifications. State the exact document and edition required by the purchase order. If the buyer does not control the edition, ask the supplier to identify the edition used in the quotation.

• ASTM A108-24 covers carbon and alloy cold-finished steel bars produced in straight lengths and coils for machining, shafting and similar applications.
• DIN EN 10278:2024-01 / EN 10278:2023 addresses dimensions and tolerances for bright steel products of stainless and other special steels when that standard is specified by contract.
• ISO 286-1:2010 and ISO 286-2:2010 define the ISO tolerance system for linear sizes and limit deviations. They do not replace the need to state the product standard and the exact feature being toleranced.

Important: naming a standard does not prove that every requested grade, shape, dimension and quantity is available. The supplier still needs to review the complete order combination.

2. Specify the Finished Section Correctly

• Round bar: state finished diameter and whether the functional requirement concerns drawing, turning, grinding or subsequent machining.
• Flat bar: state thickness x width, edge condition, flatness and the surfaces that locate the finished part.
• Square bar: state side size, corner radius, twist and which faces are functional.
• Hexagonal bar: state the across-flats dimension, corner condition and whether the bar feeds an automatic turning or fitting process.
• Custom profile: submit a dimensioned cross-section with datum faces, radii, angles and critical dimensions marked.

Use the cold drawn steel bar size range and RFQ guide to check Junxiong’s published general shape ranges before sending the enquiry.

3. Separate Dimensional Tolerance from Straightness

A diameter or across-flats tolerance controls size. It does not automatically control straightness, twist, corner radius, flatness or surface condition. These requirements should be listed separately because each affects processing and inspection.

• State the tolerance class only when the governing standard and size range are also clear.
• Use explicit upper and lower limits when a customer drawing controls the part.
• Define the measurement length and inspection method for straightness.
• For square, hexagonal and custom sections, state the allowable twist over a defined length.
• Mark functional surfaces and datums instead of applying an unnecessarily tight tolerance to every feature.

Do not copy a tolerance from a competitor table into a purchase order without confirming that it applies to the same material, shape, manufacturing route, nominal size and inspection method.

4. Define Cut Length and End Condition

Random mill length and finished fixed length are different supply routes. For a fixed-length enquiry, state the target length, plus/minus tolerance, cutting method if controlled, burr limit, chamfer, end squareness and quantity per length.

• Random length: identify the acceptable minimum and maximum range.
• Fixed length: state the finished length and tolerance for each item.
• Machining allowance: add only when the downstream process requires it.
• Ends: state as-cut, deburred, chamfered, faced or otherwise prepared.
• Packing: define bundle weight, corrosion protection, labels and shipping marks.

5. Link the Specification to the Final Application

The application helps the factory identify missing requirements. A bar for Swiss-type machining may prioritize feeding consistency and machinability. A flat bar for an armoured joint may require width, thickness, straightness, cutting and welding-related checks. A custom rail blank may need functional faces and later grinding allowance.

Application information does not authorize the supplier to guess. It is a review signal; the drawing and purchase specification remain the controlled requirements.