Cold Drawn Square Steel Bar – Sizes, Grades and Tolerances

We draw square steel bar from 4×4 mm up to 120×120 mm on our cold drawing lines. Drawing pulls hot rolled square bar through a die, which tightens the section, straightens the bar and leaves a bright, scale-free surface. If your parts are cut or machined from square stock, this is the bar that feeds consistently and holds its corner.

How We Draw Square Bar

Hot rolled square bar starts with scale on the surface. We pickle it first to remove the scale, then pull the bar through a square die on our draw bench. The die sizes the section to h11/h12 tolerance and work-hardens the outer layer, which improves surface hardness. After drawing, bars go through a roller straightener and are cut to your length with deburred ends.

Corners are the part that makes square bar different from round or flat. A rolled square has rounded corners from the rolling process. Drawing brings the corners back to a sharp 90° within ±0.5°. That matters when the bar is clamped in a vise, fed through a guide, or machined into keys and punches where the corner shape is part of the fit.

Sizes We Stock and Sizes We Draw

The sizes listed above are our common stock range. We also draw non-standard sections between 4×4 mm and 120×120 mm when the order volume makes a dedicated die worthwhile. If you need an imperial size – 1/2", 3/4", 1", 1-1/4", 1-1/2", 2" – tell us the inch size and the metric equivalent you want to match, and we confirm availability before quoting.

Surface Options

Two surface conditions are standard on our square bar:

Bright drawn (WD) – the bar is used as drawn: bright, scale-free, with the natural work-hardened surface. This is the most common choice for machining stock.

Peeled (WP) – the drawn bar is peeled to remove the decarburized layer and give a cleaner, more uniform surface. Peeling is specified when the bar goes straight into a finished part without heavy machining, or when surface quality is critical for chrome plating or induction hardening.

Both options can be oiled for rust protection on longer shipments.

Tolerance and Straightness in Practice

h11 and h12 are the two tolerance grades we draw to. For a 20×20 mm square, h11 holds the side to ±0.13 mm and h12 to ±0.21 mm. We check sides with micrometers and confirm straightness on the roller straightener before cutting. If your machining program assumes a fixed stock size, the tighter h11 bar removes the need to compensate for oversize or undersize stock.

What Customers Make From Cold Drawn Square Bar

Square bar goes into parts where a square section is the working geometry: keys and key stock, guide rails and slides, punches and die components, spindles, pins, and machine parts that are gripped or clamped by a square face. Buyers also use it for architectural and structural sections where a bright, consistent finish is part of the product appearance.

Because the drawn bar is straight and consistent from end to end, CNC shops can load it without straightening and set tool offsets once. That is usually the reason a shop switches from hot rolled square bar to cold drawn.

Quality and Inspection

Every order is produced under ISO 9001. We check the section size, corner angle, straightness and surface on the drawing line, and each batch carries an EN 10204 3.1 mill test certificate with chemical composition, mechanical properties and dimensional results. Third-party inspection can be arranged on request.

Cutting and Packing

Standard lengths are 2,000 to 6,000 mm. We cut to your exact length with a tolerance of ±2 mm on cut pieces. Bundles are tied with steel strapping and protected for container loading; cut pieces can be packed in wooden crates for sea freight. If your order is small, we still quote and ship from stock.

Lead Time and Ordering

Stock sizes ship within 3–7 days. Custom sections and non-standard sizes take 15–25 days depending on quantity and die preparation. Send us the size, grade, length, quantity and destination port, and we come back with a price and delivery date. We also draw square steel in higher grades, round bar and flat steel on the same lines.

Selecting the Right Square Size

Square bar is specified by side dimension, and the stock sizes above cover the range that machine shops actually order. As a rule of thumb, pick the smallest square that machines to your finished part without an oversize allowance – a 20×20 mm bar finishing to 19 mm parts wastes less than a 25×25 mm bar doing the same job. If the part is cut from bar on a saw, add 3–5 mm per cut for saw kerf and facing. We quote cut-to-length pieces with ±2 mm length tolerance, so you can order exactly the number of blanks you need.

Square Bar on CNC and Bar Feeders

A drawn square feeds differently than round stock. On CNC lathes and bar feeders that accept hex or square stock, the flat faces give the guide bushing a stable surface to grip, and the sharp 90° corners stop the bar from rotating in the feeder. On machining centres, the square section clamps squarely in a vise – two flat faces give you a repeatable datum without soft jaws. The drawn tolerance means the bar is already at nominal size, so your program can use a fixed stock allowance instead of probing each bar.

Square vs Round Stock: When to Choose Square

Round bar is the default when the finished part is a shaft or turned component. Square wins when the part has flats, keyways, a square cross-section, or when it is held or driven by a square face – keys, punches, guide rails, spindles with square shoulders. Drawing square bar also removes material before you machine: a 30 mm square part from 30 mm square bar starts at finished size, whereas from 40 mm round you would turn away more than a third of the material.

Jigs, Keys and Tooling

Square drawn bar is the standard stock for parallel keys and key stock, which sit in keyways and transmit torque between shaft and hub. The sharp corners and straight sides matter here: a key with rounded corners does not seat fully and can rock under load. The same properties suit punches, die pins and guide rails, where the square section is part of the working geometry. If you machine keys from square stock, order the bar at the key width so only the length needs cutting.

Inspection and Documentation

We check side dimension, corner angle, straightness and surface on the drawing line. Each order can carry an EN 10204 3.1 mill test certificate with chemical composition, mechanical properties and dimensional results. CE and ISO 9001 documentation are available with the shipment. Third-party inspection is arranged on request, and bars can be stamped or tagged to your marking instruction.

Stock Program and Delivery

Common square sections are held in stock in Q235 and C45: 10×10, 12×12, 16×16, 20×20, 25×25, 30×30, 40×40, 50×50 and 60×60 mm. Stock sizes ship within 3–7 working days. Alloy and hardened grades – Q345B, 45#, 40Cr, 42CrMo – are drawn to order in 15–25 days depending on heat availability.

Bars are supplied in 3–6 m lengths or cut to your blanks with ±2 mm tolerance and deburred ends. Bundles are steel-strapped; cut pieces and small orders are crated with dunnage. Minimum order is 500 kg per size, combined across a mixed order. If you are qualifying us as a new supplier, a one-ton mixed trial order is the practical entry point.