Engineering Design · series, slot codes, naming

Aluminium Profile Basics: What the Series Numbers and Slot Codes Mean

A code such as 4040 means a 40 × 40 mm envelope; 2020 is 20 × 20 mm and 4590 is 45 × 90 mm. The series digit locks the slot family that your nuts and brackets must match, not just the outer size.

Naming rule: Digits = envelope in mm
Example section: 45 × 90 mm, 4.10 kg/m, I ≈ 68 cm⁴
Slot families: 6 mm / 8 mm / 10 mm mouths
Read: 8 minutes

Stack of silver anodised T-slot aluminium extrusions on a factory bench

Short answer

Read a metric T-slot code as millimetres: the first pair is one side of the envelope, the second pair is the other, so 3030 is 30 × 30 mm and 4080 is 40 × 80 mm. The series (20, 30, 40, 45, 50) usually fixes the slot mouth — 6 mm on 20 series, 8 mm on most 30 and 40 series, 10 mm on 45 series and many heavier frames — which is what decides hardware. For a worked mass and stiffness figure, a 45 × 90 mm six-slot 6063-T5 bar is 4.10 kg/m with I ≈ 68 cm⁴ on the strong axis. Pick series by load band and slot first; treat catalogue names such as PG40 as branded 40-series lines until you have a dimensioned section, not as proof of interchange.

The digits name the envelope in millimetres; the slot mouth — not the outer size alone — decides which nut fits.

What does 2020 mean in aluminium extrusion

2020 means a 20 × 20 mm square envelope on the metric naming system; the same pattern scales to every common square and rectangular code.

The first two digits are one outer side in millimetres and the second two digits are the other. Rectangular bars keep the series slot: a 2040 uses the same 6 mm mouth as a 2020, and a 4080 usually shares the 8 mm mouth of a 4040. The name is not a wall thickness, not a mass, and not a hardware guarantee — those come from the section drawing and the slot table. Copy the mapping below onto a first RFQ so purchasing and design use one language.

Code	Envelope	Typical series / slot	What the digits are	What they are not
2020	20 × 20 mm	20 series / 6 mm	Outer width × height	Wall or kg/m
2040	20 × 40 mm	20 series / 6 mm	Same series, deeper rail	A different nut family
3030	30 × 30 mm	30 series / 8 mm	Outer width × height	Interchange with 20-series hardware
4040	40 × 40 mm	40 series / 8 mm (some 10)	Outer width × height	Proof of brand compatibility
4080	40 × 80 mm	40 series / 8 mm	Rectangular envelope	Twice the slot mouth
4545 / 4590	45 × 45 / 45 × 90 mm	45 series / 10 mm	Outer sides in mm	Same nuts as 8 mm systems

Which series profile to use (by series)

Choose the series by the governing constraint — span, joint load or plant hardware standard — then keep one series across the frame so T-nuts stay interchangeable.

20 series suits short, light members. 30 and 40 series cover most OEM workbenches and machine frames on an 8 mm mouth. 45 series steps the mouth to 10 mm for heavier lips and larger nuts. 50 series is for machine bases and long uprights where mass and I dominate. The table is a selection band, not a substitute for a deflection check: aluminium’s modulus is near 69 GPa, so serviceability usually fails before yield.

Series	Slot	Typical use	Load band	Verdict
20 series	6 mm	Fixtures, sensor mounts, light guards, short lab rails	Light; short spans	Use when mass and envelope must stay minimal
30 series	8 mm	Mid benches, small machine frames, panel posts	Light–medium	Good step up from 2020 without 40-series mass
40 series	8 mm (some 10)	Industrial workbenches, conveyors, robot fences	Medium; plant default	Default OEM framing series in Europe and export kits
45 series	10 mm	Heavy benches, welding tables, tall uprights	Medium–heavy	Pick when joint preload and lip thickness matter
50 series	10 mm class	Machine bases, long gantries, high uprights	Heavy	Use when span and vibration outgrow 40/45

A concrete stiffness example: the site’s 45 × 90 mm six-slot 6063-T5 section at 4.10 kg/m with I ≈ 68 cm⁴ sits well above a light 4040 for bending, which is why rectangular 45-series rails appear on long top beams. For metre price and tooling share see how die cost amortises per meter; for order floors see minimum order with a new die.

What is pg40 vs 40 series

PG40 is a catalogue or brand line name for a 40 mm-class profile with a declared accessory set; “40 series” only promises a 40 mm envelope family unless the supplier also states the slot geometry.

Buyers mix the two terms because many Asian catalogues prefix square sections with PG (or similar) and a size digit. That label often implies a matched T-nut, bracket and core-hole anchor kit. A generic 40-series call-out without mouth, undercut and core-hole dimensions does not prove those accessories will fit. Before substituting PG40 hardware onto a generic bar — or the reverse — require a dimensioned section with slot mouth, lip and core hole, then fit-test the actual nut. Envelope, weight and 2026 USD per metre say nothing about interchange. Cross-brand notes live with hardware compatibility; this page only settles the naming confusion.

What is a t-slot aluminium profile used for

T-slot aluminium profiles are used to build reconfigurable industrial frames — workbenches, machine bases, guards, conveyors, test rigs and automation cells — where bolted joints beat welded steel for layout changes.

The continuous slot accepts T-nuts anywhere along the length, so panels, hinges, cable trays and actuators mount without drilling every new hole in the primary members. OEM and integrator buyers specify a series once, then cut and join bars into kits that assemble on site. Typical 6063-T5 framing balances finish quality with adequate strength; move to higher-yield alloys only when the drawing demands it. Secondary work — cut length, holes, taps — turns stock bars into kit members; calendar and die questions sit on die making adds 7–12 days and who owns the die.

RFQ checklist — naming a first profile order

Envelope code — e.g. 4040 or 45 × 90 mm, written as millimetres.
Series and slot mouth — 6, 8 or 10 mm, not assumed from the envelope alone.
Alloy / temper — usually 6063-T5 for framing.
Mass / I if structural — kg/m and cm⁴ when span governs.
Hardware set — whether existing nuts/brackets must be reused.
Finish — mill or anodised, and which faces are cosmetic.

Put both the envelope and the slot mouth on the PO. A “4040” line without “8 mm slot” leaves the fastener ambiguous.

Related on this site

how die cost amortises per meter — tooling share inside the metre price
minimum order with a new die — 150 m existing vs 500 m new
die making adds 7–12 days — calendar before first bars
who owns the die — tooling title after the trial

Terms used in this article

Series: The envelope family (20, 30, 40, 45, 50…) that usually locks the slot mouth and hardware set.
Envelope: The outer width × height of the profile in millimetres, as named by codes such as 4040.
Slot mouth: The narrow opening at the face of a T-slot; the dimension a nut must pass.
PG40: A catalogue or brand line name for a 40 mm-class profile with a declared accessory set, not a universal standard.
Moment of inertia (I): Section property that sets bending stiffness for a given span and load.

Questions buyers ask

What does the first number mean?

On metric codes the first digit pair is one outer side in millimetres and the second pair is the other side. In 4040 both sides are 40 mm; in 4080 one side is 40 mm and the other is 80 mm. The digits never state wall thickness or slot mouth by themselves — those belong on the section drawing.

What is a slot?

A T-slot is the continuous groove along the profile face that accepts a T-nut or panel fastener. The critical width is the mouth at the face (commonly 6, 8 or 10 mm). The undercut behind the lips is what the nut flanges lock into; without that undercut a bolt has nothing to pull against.

What is the difference between series?

Series change the envelope, the usual slot mouth and the load band. 20 series uses a 6 mm mouth for light work; 30 and most 40 series use 8 mm; 45 and many heavy frames use 10 mm. Hardware from one mouth family will not fit another even when the outer sizes look similar in a photograph.

Which series is most common?

For industrial export framing the 40 series with an 8 mm slot is the volume default on workbenches and machine guards. 30 series appears on lighter benches; 45 series appears when joints and spans outgrow 40. Lock one series for the whole cell so nuts and brackets stay interchangeable.

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Send the series and slot you intend to standardise

State the envelope code, the slot mouth and whether existing hardware must be reused. We will confirm the section against a dimensioned drawing before you lock the BOM.

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