Four open slots
The standard layout: a slot on every face, so brackets and panels can be fixed from any side.
40 mm metric T-slot framing
4040 / 4080 Aluminium T-Slot Extrusion
4040 and 4080 are the 40 mm metric T-slot profiles used for machine frames, guarding, workstations and automation cells: a 40 × 40 mm square section and a 40 × 80 mm double section with open slots that take nuts, brackets and panels without welding. Metline supplies both in 8 mm and 10 mm slot versions, light and heavy walls, clear or black anodised, cut to length and shipped worldwide.
- Sections
- 40 × 40 mm, 40 × 80 mm
- Slot width
- 8 mm or 10 mm
- Alloys
- 6063, 6105, 6061
- Lengths
- Up to 6 m or cut to size
What are 4040 and 4080 aluminium extrusions?
The numbers describe the outside section in millimetres: a 4040 profile is 40 × 40 mm, a 4080 is 40 × 80 mm. Both belong to the "40 series", the most widely used size class in metric modular framing, sitting between the light 20 and 30 series and the heavy 45, 50 and 80 series.
Each profile is a hollow extrusion with a central core bore and an undercut T-slot in each face. A T-nut slides or drops into the slot and a bolt passes through a bracket into the nut, so frames go together with hand tools and can be taken apart, extended or rebuilt later. The core bore can be tapped (typically M8 for 8 mm slot profiles and M10 or M12 for heavier 10 mm slot profiles, depending on the design) for end fastening.
A 4040 is the default for frames of moderate size: machine guards, operator workstations, 3D printer and CNC router bases, test rigs and enclosures. A 4080 is two 40 mm modules side by side. Its height on the strong axis gives it far more bending stiffness in that direction, so it is used for long spans, gantry beams, base frames, conveyor side rails and anywhere a single member carries most of the load.
8 mm and 10 mm slot: which system do you need?
There is no single international standard for T-slot geometry. The two common 40 series families are the "slot 8" system and the "slot 10" system, and within each family the inner shape of the slot, the depth of the undercut and the core bore vary from one system brand to another. Fasteners from one family will not fit the other, and even within a family it is worth checking the slot drawing before mixing brands.
| Feature | 40 series, 8 mm slot | 40 series, 10 mm slot |
|---|---|---|
| Slot opening | 8 mm (often 8.0 – 8.2 mm) | 10 mm (often 10.0 – 10.2 mm) |
| Typical fastener | M4 – M8 T-nuts and hammer nuts | M5 – M8 T-nuts and hammer nuts |
| Common in | European modular systems, machine building | Asian and some European systems, heavier hardware |
| Panel infill | 4 – 6 mm panels in a slot gasket | 4 – 8 mm panels in a slot gasket |
| Best for | Compatibility with existing 8 mm frames | Heavier brackets and larger nuts |
Slot dimensions and fastener sizes above are typical ranges. Send the profile drawing or the system you already use, and we will match the profile to it.
Some systems also use a drop-lock or taper feature: the inner flanges of the slot are angled a few degrees so that tightening the nut pulls the flanges in and locks the joint against vibration. If your frame relies on this, tell us, because a profile without the taper will hold a joint but will not give the same pre-load.
Light, standard and heavy 4040 / 4080 profiles
The same 40 × 40 mm outside size is made with very different wall thicknesses and core shapes. Weight and stiffness can differ by 50 % or more between a light and a heavy version, so compare the moment of inertia, not just the nominal size, before you substitute one profile for another.
| Profile | Typical weight (kg/m) | Moment of inertia I (cm4) | Typical use |
|---|---|---|---|
| 4040 light / economy | 1.35 – 1.55 | 6.5 – 7.5 | Guards, light frames, displays |
| 4040 standard | 1.7 – 1.9 | 9 – 10.5 | General frames, workstations, enclosures |
| 4040 heavy | 2.3 – 2.5 | 13 – 14.5 | Machine frames, high-load uprights |
| 4080 light | 2.1 – 2.3 | about 45 (strong axis) | Long light beams, conveyor rails |
| 4080 standard | 2.7 – 2.9 | about 55 – 62 (strong axis); 15 – 17 (weak axis) | Gantries, base frames, beams |
Indicative ranges compiled from published data for common 40 series systems. Exact section properties depend on the die; we supply the drawing and section data for the profile quoted.
One, two or three closed faces
Smooth faces where a slot is not needed: cleaner look, easier to wipe in cleanrooms and food areas, and fewer dirt traps.
Radius and 45° profiles
Rounded or angled corner sections for operator-safe edges, curved enclosures and frames at angles other than 90°.
4080 with 6 or 8 slots
Double profiles with slots on the narrow faces as well as two slots on each wide face, for mounting rails and guards side by side.
Slot covers and gaskets
Plastic or aluminium cover strips close unused slots; panel gaskets hold infill panels without rattling.
Machined profiles
Tapped core bores, counterbored access holes for anchor fasteners and mitred ends prepared before dispatch.
Alloys, tempers and mechanical properties
T-slot profiles are extruded from medium-strength 6xxx alloys that extrude well through complex hollow dies and anodise evenly. The choice affects strength more than stiffness: every aluminium alloy has an elastic modulus close to 69 GPa, so a heavier profile, not a stronger alloy, is the way to reduce deflection.
| Alloy and temper | Min. tensile strength | Min. yield strength (0.2 %) | Standard | Notes |
|---|---|---|---|---|
| 6063-T5 | 175 MPa (wall ≤ 10 mm) | 130 MPa | EN 755-2 | Best surface for anodising; light and standard profiles |
| 6063-T6 | 215 MPa (wall ≤ 10 mm) | 170 MPa | EN 755-2 | Common for general framing |
| 6063-T66 | 245 MPa (wall ≤ 10 mm) | 200 MPa | EN 755-2 | Higher-strength 6063 variant |
| 6105-T5 | 262 MPa / 38 ksi | 241 MPa / 35 ksi | ASTM B221 | Widely used for strong framing profiles in North America |
| 6061-T6 | 260 MPa / 38 ksi | 240 MPa / 35 ksi | ASTM B221 / EN 755-2 | High strength; used for special heavy sections |
Physical properties (6063 / 6105, typical)
- Density
- 2.70 g/cm³
- Modulus of elasticity
- about 69 GPa (10,000 ksi)
- Thermal conductivity
- about 190 – 210 W/m·K depending on alloy and temper
- Coefficient of thermal expansion
- about 23 µm/m·°C
- Electrical conductivity
- roughly 45 – 55 % IACS
- Magnetic
- Non-magnetic
Specified minimums are what the standard guarantees; typical values are higher. The mill test certificate for each lot reports actual results.
How much load can a 4040 or 4080 carry?
For T-slot frames, deflection usually decides the profile long before strength does. A quick check uses the beam formula for a simply supported member with a load at mid-span: deflection = F × L³ / (48 × E × I).
Worked example: a 1,000 mm long standard 4040 (I ≈ 9 cm4 = 90,000 mm4, E = 69,000 MPa) carrying 1,000 N (about 100 kg) at the centre deflects 1,000 × 1,000³ / (48 × 69,000 × 90,000) ≈ 3.4 mm. The same load on a standard 4080 with the 80 mm side upright (I ≈ 58 cm4) deflects only about 0.5 mm. Double the span and deflection rises eight times, which is why long beams move up to 4080 or larger sections quickly.
| Span, centre load 500 N | 4040 standard (I ≈ 9 cm4) | 4080 standard, strong axis (I ≈ 58 cm4) |
|---|---|---|
| 500 mm | 0.21 mm | 0.03 mm |
| 750 mm | 0.71 mm | 0.11 mm |
| 1000 mm | 1.68 mm | 0.26 mm |
| 1250 mm | 3.28 mm | 0.51 mm |
| 1500 mm | 5.66 mm | 0.88 mm |
| 2000 mm | 13.42 mm | 2.08 mm |
Calculated for a simply supported beam with a single central load; self-weight and joint flexibility are ignored. Fixed ends roughly quarter the deflection. Use the exact I value from the profile drawing for design.
- Aim for deflection below about L/500 on machine frames that carry precision equipment, and below L/200 for general guarding
- Joints are rarely fully rigid: corner gussets and diagonal braces add more stiffness than a heavier profile alone
- Check fastener pull-out and bracket strength for point loads, not just the profile
- For dynamic loads such as gantries and robots, size for stiffness and natural frequency, not static strength
Anodising and other finishes
T-slot profiles are almost always supplied anodised. A clear anodic film (typically 10 – 15 µm for indoor framing, 20 µm or more where the frame faces weather or cleaning chemicals) protects the surface, resists fingerprints and gives the even satin look buyers expect. Black anodising is the next most common choice for machine builders and display frames; colours such as yellow are used for safety barriers.
Clear anodised
Standard satin silver. Hard, wear-resistant surface that does not chip because it is part of the metal.
Black anodised
Popular for machines, photography rigs and displays. Slight colour variation between batches is normal; order a frame from one batch where appearance matters.
Powder coating
Any RAL colour. Check slot tolerance: a thick coating inside the slot can stop nuts sliding, so slots are often masked.
Mill finish
Unfinished extrusion for frames that will be painted or hidden. Cheaper, but marks easily in handling.
Remember that saw-cut ends and any machined holes expose bare aluminium after anodising. This is normal and does not affect corrosion resistance indoors; end caps cover the cut face for a finished look and safety.
Lengths, cutting and tolerances
Supply range
- Sections
- 4040 and 4080 in light, standard and heavy versions; 4040 with closed faces, radius and 45° profiles
- Slot width
- 8 mm or 10 mm systems; other systems matched to drawing
- Mill lengths
- Typically 3 m, 4 m, 5.8 m or 6 m stock lengths
- Cut lengths
- Precision saw-cut to your cut list, square or mitred
- Machining
- Core tapping, access holes for anchor fasteners, drilling and slotting to drawing
- Supply as
- Cut lengths only, machined kits ready to assemble, or kits with fasteners and accessories
| Characteristic | Typical requirement |
|---|---|
| Cross-section dimensions | To EN 755-9 or the system drawing; slot opening usually held to about +0.1 / −0 mm |
| Straightness | In the order of 0.5 mm per metre or better on precision framing profiles |
| Twist | In the order of 0.5° per metre or better |
| Cut length | Commonly ±0.2 – 0.5 mm on precision saws |
| End squareness | Square cut within a few tenths of a degree, so joints close without gaps |
Tighter straightness, twist or length tolerances can be agreed per order. State them on the drawing so they appear on the inspection report.
Where 4040 and 4080 profiles are used
- Machine guarding and safety fencing: 4040 posts with mesh or polycarbonate infill around robots and presses
- Workstations and assembly benches: adjustable shelves, tool rails, lighting and monitor arms clamp straight to the slots
- Automation and gantries: 4080 beams carry linear guides, belts and cable chains
- CNC routers, laser engravers and 3D printers: rigid bases and gantry beams built without welding
- Conveyor frames: 4080 side rails with 4040 legs and cross members
- Cleanroom and laboratory frames: closed-face profiles for wipe-down surfaces
- Enclosures and control cabinets: panels fitted into slot gaskets, doors hinged on slot-mounted hinges
- Exhibition stands, carts and test rigs: reusable structures that change with the project
Compared with welded steel frames, an aluminium T-slot frame weighs roughly a third as much for the same outside size, needs no painting, and can be changed on the shop floor. Steel still wins on raw stiffness per section size, which is why heavily loaded machine beds often combine a steel base with an aluminium superstructure.
How to order 4040 / 4080 profiles from Metline
- SpecifyProfile (4040 or 4080), slot width, light / standard / heavy version or drawing, alloy if specified, finish and colour.
- Cut listSend lengths and quantities per length, plus any tapping, holes or mitres, or a frame drawing for us to break down.
- QuoteWe confirm the profile drawing, section data, tolerances, accessories and delivery terms (EXW, FOB, CIF or DAP).
- InspectProfiles are checked for section, straightness, cut length and finish; a mill test certificate to EN 10204 3.1 is available.
- Pack and shipFilm-wrapped, bundled or kit-packed and labelled by part number, in export cases or pallets by sea or air.
References and standards
- EN 755-2 – Aluminium and aluminium alloys: extruded rod/bar, tube and profiles, mechanical properties
- EN 755-9 – Extruded rod/bar, tube and profiles: profiles, tolerances on dimensions and form
- ASTM B221 – Standard Specification for Aluminum and Aluminum-Alloy Extruded Bars, Rods, Wire, Profiles, and Tubes
- EN 573-3 – Chemical composition and form of wrought products
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits
4040 / 4080 aluminium (aluminum) extrusion: frequently asked questions
What is a 4040 aluminium extrusion?
A 4040 is a metric T-slot framing profile with a 40 × 40 mm square section and a T-slot on each face, usually extruded in 6063 or 6105 aluminium and anodised. It is the standard size for machine guards, workstations, enclosures and medium-duty frames.
How much does 4040 aluminium extrusion weigh per metre?
Between about 1.35 and 2.5 kg per metre, depending on whether it is a light, standard or heavy profile. A standard 8 mm slot 4040 weighs around 1.8 kg/m and a standard 4080 around 2.8 kg/m.
Will 8 mm slot nuts fit a 10 mm slot profile?
No. The two slot systems use different nut widths and slot undercuts. Choose one system for the whole frame, and check the slot drawing even within the same slot width if you mix brands.
Is 4080 twice as strong as 4040?
In bending about its strong axis a 4080 is roughly five to six times stiffer than a 4040, because stiffness rises with the cube of section height. About its weak axis it is only modestly stiffer. Always orient a 4080 with the 80 mm side in the direction of the load.
How is a 4040 / 4080 frame joined without welding?
With T-nuts and bolts through corner brackets, gussets and joining plates, or with internal anchor fasteners that pass through a drilled access hole into a tapped core bore. Internal fasteners give a clean look; gussets give the most rigid corners.
Can you supply the profiles cut and machined as a kit?
Yes. Metline can cut profiles to your list, tap core bores, drill access holes and pack each frame as a labelled kit with brackets and fasteners, ready to assemble on arrival.
Building a 4040 or 4080 frame?
Send the drawing or cut list, slot system and finish. We will reply with the profile data, a full kit price and delivery to your site.
