Aluminum Square & Rectangular Tube | Sizes, Load Guide, Cut-to-Length, Custom Extrusion

Aluminum Square Tube and Rectangular Tube—Standard Sizes or Custom Extrusion, Machined to Your Cut List

“What size do I need?” is the first question. “Can you cut it, drill it, and bend it?” is the second. “Will it stay straight?” is the third. Here are straight answers to all three, plus the details that don’t show up on a standard spec sheet.

We make aluminum square tube and rectangular tube. The kind used for machine frames, conveyor legs, railing posts, solar mounting rails, trailer structures, and a hundred other things that need to be light, strong, and straight.

Two ways to buy from us. If your design uses a standard size—50×50, 40×40, 80×40, that sort of thing—we probably already have the die. No tooling charge, just tell us the alloy, wall thickness, finish, and cut length. If your design needs something non-standard—a specific corner radius, an unusual wall thickness, a size that’s off the catalog—we cut a new die and extrude it to your drawing. Either way, the tube arrives cut to length, drilled if you want it, tapped if you need it, labeled to match your BOM.

Questions That Come Up on Almost Every Order

“Do I want square tube or rectangular tube?”

Square tube is 50×50 or 40×40. Rectangular tube is 80×40 or 60×30—taller than it is wide. The choice comes down to which direction the load acts in.

Square tube is equal in both directions. Use it for vertical posts, columns, railing uprights—anything where the force could come from any side. Rectangular tube puts more material in the tall direction, which is where bending resistance comes from. For a horizontal beam supporting weight across a span, 80×40 in the vertical orientation beats 50×50 on stiffness for roughly the same weight per meter.

A quick way to think about it: if the part stands upright and takes compression, square is usually right. If the part spans horizontally and takes bending, rectangular is usually more efficient. If you’re not sure, tell us where the load is and we’ll help you pick.

“What size do I need for a 1.5-meter span carrying 100 kg?”

This question comes in different versions, but the shape is always the same: a span, a load, and a worry about whether the tube will sag or fail.

There’s no single answer without knowing the details—concentrated load or distributed, supported at both ends or cantilevered, static or dynamic. But for a rough starting point, assuming evenly distributed load and simple supports:

Span	Light load (under 30 kg)	Medium load (30–100 kg)	Heavy load (over 100 kg or point load)
Up to 0.8 m	30×30×2.0 mm	40×40×2.5 mm	50×50×3.0 mm
0.8–1.5 m	40×40×2.5 mm	50×50×3.0 mm	60×40×3.0 mm
1.5–2.5 m	50×50×3.0 mm	60×40×3.5 mm	80×40×4.0 mm
Over 2.5 m	Don’t guess—send us the details	80×40×4.0 mm or heavier	Needs proper calculation

This table assumes 6063-T5. If you step up to 6061-T6, you can often use a smaller section for the same load because 6061-T6 has roughly 50% more yield strength than 6063-T5. That’s useful when space is tight or when you’re trying to keep the structure light.

One more thing: if this is for anything where failure could hurt someone—a walkway, a raised platform, a vehicle structure—don’t use a table. Send us the load case and we’ll check the section against the applicable standard.

“Can you bend aluminum square tube?”

Yes, within limits. Small sections bend easily. Large sections don’t. Thin walls wrinkle on the inside of the bend. Thick walls fight the bender.

Some practical numbers from what we run in production:

• Sections up to about 40×40 mm bend reliably with standard tooling
• 50×50 mm and larger can usually be bent, but the bend radius needs to be generous and the wall thickness needs to support the bend
• Minimum practical bend radius for square tube is roughly 3 times the section size, measured to the centerline. Tighter than that and the inside wall starts to cave
• 6063 bends better than 6061. 6061-T6 is hard and tends to crack on tight bends unless it’s annealed first, which adds cost and time
• Bending a tube before surface finishing usually works better than bending a finished tube. The bend zone will show tooling marks

If you need curved tube, send us the bend radius, arc length, and section size. We’ll tell you what’s doable and what will need a design change.

“Why do different suppliers quote such different prices for the same 50×50×3.0 tube?”

Same dimensions on paper. Different product in reality. Here’s what drives the price spread:

1. Wall thickness tolerance. A “50×50×3.0” tube might be produced at 2.7 mm actual wall if the supplier is running to the loose end of the tolerance. Less aluminum per meter, lower price. We hold wall thickness to the tighter end of the GB/T 5237.1 range, and we tell you which tolerance level you’re getting.
2. Billet quality. Tube made from remelted scrap has more iron, more inclusions, and a duller surface after anodizing. Tube made from clean primary aluminum costs a bit more per kilo and looks completely different on a finished product.
3. Straightening. Tension-stretched tube stays straight after cutting. Tube that’s just been rolled through a straightener can spring back when you cut it into short lengths. We tension-stretch everything.
4. Delivery condition. A 6-meter raw bar costs less than a pre-cut, deburred, labeled piece. The raw bar also leaves you with the sawing, the scrap, and the labor.

We quote with the tolerance standard, the billet source, the straightening method, and the delivery condition spelled out. You can compare our price to another supplier’s price on an apples-to-apples basis.

“6063 or 6061? Does it actually matter for my project?”

It matters more than most people expect.

	6063-T5	6061-T6
Tensile strength	160 MPa	290 MPa
Yield strength	110 MPa	240 MPa
Price	Lower	Higher
Anodized appearance	Clean, bright, even	Greyish, less uniform
Welding	Acceptable for light loads	Excellent
Bending	Good	Poor without annealing
Best use	Railings, decorative parts, light frames	Machine structures, vehicle parts, load-bearing welded assemblies

The one-line answer: if it’s decorative or lightly loaded, use 6063-T5. If it’s structural, welded, or safety-related, use 6061-T6.

We also supply 6005-T5 for solar mounting and rail applications—stronger than 6063-T5, extrudable at reasonable speeds, and commonly specified for photovoltaic support structures.

Where These Tubes Used

Machine frames and equipment bases

Conveyor legs in 50×50×3.0, cross beams in 80×40×3.0, all 6061-T6 when the loads are real. Straightness matters because a bowed frame member makes the whole machine sit crooked. We hold 0.5 mm per meter and check every bar before it’s cut.

Railings, balustrades, and guardrails

Usually 6063-T5, 40×40 or 50×50 for posts, smaller sections for infill. The surface finish does the heavy lifting here—outdoor railings need AA15 or AA20 anodizing with proper sealing, or super-durable powder coat. Standard AA10 looks fine indoors and degrades outdoors.

Solar mounting structures

Ground-mount posts in 100×50 or 80×80, often in 6005-T5. Roof-mount rails in smaller rectangular sections. 25-year outdoor exposure means the anodizing specification matters as much as the alloy choice. We’ve written more about this on our solar mounting page.

Vehicle and trailer structures

Main rails in 100×50×4.0 or heavier, 6061-T6, welded. This is where the strength difference between 6063 and 6061 really shows up. A trailer frame built from 6063 would be a liability. 6061-T6 is the standard for a reason.

Exhibition and display frames

Light, modular, and presentable. 40×40 and 25×25 in 6063-T5 with anodized or powder coated finish. The key requirement is that the visible surfaces look clean and the pieces fit together without hammering.

What We Do in the Factory

Extrusion

Billet heated to 480–520°C and pushed through the die. 6063 runs fast. 6061 runs slower and wears dies faster, which is part of why it costs more. We hold section dimensions to GB/T 5237.1 and check every 50 bars.

Straightening

Every tube goes through a tension stretcher after extrusion. This is the step that makes the difference between a tube that’s straight today and a tube that’s straight after it’s been cut into ten pieces. We stretch 1–3% past yield.

Cutting

Precision saw, ±0.1 mm on length, ends square and burr-free. Cut lists from your drawing or BOM. We can also miter-cut for welded or bonded corners.

Drilling and tapping

CNC drilling from a single datum, hole position ±0.15 mm. Tapping to 6H class, M3 through M12. Thread milling where the design calls for it.

Bending

Rotary draw bending and roll bending for curved sections. Evaluation based on your radius, section, and wall thickness before we commit.

Surface finishing

Anodizing to AA10, AA15, or AA20 with nickel salt sealing. Powder coating with standard polyester, super-durable polyester, or PVDF. All finishing done in-house, so the tube doesn’t leave the building between machining and coating.

Packing

Protective film on visible surfaces, foam separators between layers, stretch wrap for moisture protection. Pallets or crates for export. Labels on every piece if you’re ordering a kit.

FAQ

Q1: Do you hold stock, or is everything custom extruded?

A: We maintain existing tooling for dozens of standard sizes (ranging from 20×20 mm to 100×100 mm square, and up to 150×50 mm rectangular, with wall thicknesses from 1.5 mm to 6.0 mm). For standard profiles, there are no die charges. If your design requires a custom profile, custom wall profile, or specific corner radius, we manufacture new tooling in-house. Custom die lead time is typically 10–14 days.

Q2: What tolerances can you hold on cut length and hole positions?

A: For standard extrusion cross-sections, we comply with GB/T 5237.1 and EN 755-9. For precision post-processing, our CNC cutting holds lengths to ±0.1 mm, and hole-to-hole location tolerances to ±0.15 mm. If your assembly requires tighter linear or twist tolerances, we can precision-mill key surfaces.

Q3: How do you prevent surface scratching during sea freight transit?

A: Every tube receives a protective PE surface film on visible faces. Profiles are bundled with interleave foam separators to prevent metal-to-metal contact, wrapped in waterproof stretch film, and packed into steel-reinforced wooden crates. For high-density shipping, we can nest smaller profile sizes inside larger tubes upon request to optimize container space.

Q4: Can you supply Mill Test Certificates (MTCs) and material traceability?

A: Yes. Every shipment includes an EN 10204 3.1 Mill Test Certificate detailing heat numbers, chemical composition (Si, Fe, Cu, Mn, Mg, Cr, Zn, Ti), and mechanical testing (tensile strength, yield strength, elongation, and Webster hardness). Third-party inspections (SGS, TUV, Bureau Veritas) can be arranged prior to shipment.

Q5: What is the impact of welding on 6061-T6 aluminum tube strength?

A: Heat from welding reduces the yield strength in the Heat-Affected Zone (HAZ) of 6061-T6 by roughly 40–50% (effectively dropping it down to a T4 temper state). For structural or load-bearing welded assemblies, you must either account for this derating in your structural calculations or perform post-weld solution heat treatment and artificial aging (T6 restoration).