Strut Aluminium Profile 20×40 mm 2-Slot T-Slot Extrusion for Light Frames

OEM / ODM Available Free Sample Available ISO 9001:2015 EN 755-9 RoHS REACH

20 x 40 mm two-slot T-slot strut aluminium profile in 6063-T5 with two M6 slots on a 20 mm pitch and an M6 centre bore. A light, low-cost member for display frames, small guards, benches and growing racks.

Wholesale Price $1.35 - $2.20 / m per m

Material	Aluminium
Alloy Grade	6063-T5
Temper	T5
Section Size	40 x 20 mm
Slot	M6 slot, 6.2 mm mouth, 2 slots, 20 mm pitch
Length	6 m stock, cut to drawing to plus or minus 0.5 mm
Tolerance	EN 755-9 / GB/T 6892, wall plus or minus 0.15 mm
Surface	Mill finish / clear anodised / black anodised
MOQ	1000
Lead Time	18-28 days after deposit for mill finish
Loading Port	Shanghai / Ningbo
Supply Ability	550 t per month
Payment Terms	T/T 30% deposit + 70% before shipment \| L/C at sight
Trade Terms	FOB \| CIF \| EXW
Certifications	ISO 9001:2015 \| EN 755-9 \| RoHS \| REACH

Request a Quote Reply within 24 hours

Light framing · 20 series

A 20 x 40 two-slot strut profile is a light T-slot aluminium extrusion with a 40 mm wide face carrying two parallel slots on a 20 mm pitch and an overall height of 20 mm. It sits at the light end of the framing range and is specified where a frame has to hold its shape, be cheap enough to build in quantity and light enough to be moved by hand: display frames, light machine guards, small benches, camera and sensor mounts, and the internal frames of control enclosures.

It is extruded in 6063-T5 with M6 slots on a 6.2 mm mouth and a O 5 mm centre bore tapped M6, and weighs about 1.05 kg/m on a 1.8 mm wall, so a 6 m length is a one-person lift. The two-slot layout is what separates it from a 20 x 20 single-slot section: the 40 mm face gives two independent fixing lines, so a panel or a shelf can be held along two edges without an extra bracket, and the section is far stiffer across its 20 mm height than a 20 x 20. Where it stops being enough, the correct move is up to the 30 series rather than a heavier wall in this die.

20 x 40 two-slot section: 40 mm wide face, two slots on a 20 mm pitch, M6 slot mouths (6.2 mm), O 5 mm centre bore tapped M6.

Where the light end of the range actually ends

Light framing fails in one of three ways, and it is worth knowing which one applies before a section is chosen. The first is deflection: the member bends visibly under load and the frame looks wrong even though nothing has broken. The second is a joint that will not hold, where the bolt is fine but the wall it is anchored in is too thin, so the thread strips or the slot lips open. The third is assembly, where a frame is stiff enough but fiddly to build because the fixing points sit too far apart.

A 20 x 40 addresses the third case well and the first two up to a point. Two slots on a 20 mm pitch give four usable fixing positions across the face instead of two, which makes a small frame much quicker to square up. But the 1.8 mm wall sets a ceiling on torque: the section is designed for M6 fixings at modest tightening values, not for the torque used on 40 series. If a joint has to be tightened hard and left, this is the wrong section and no amount of extra brackets will fix it.

Property	20 x 20 single slot	20 x 40 two slot	30 x 30 four slot
Envelope	20 x 20 mm	40 x 20 mm	30 x 30 mm
Slots	1 (M5)	2 (M6)	4 (M6)
Slot pitch	not applicable	20 mm	15 mm
Centre bore	O 4.2 mm, tapped M5	O 5 mm, tapped M6	O 8.2 mm, tapped M8
Wall	approx. 1.5 mm	approx. 1.8 mm	approx. 1.8 mm
Moment of inertia	approx. 0.6 cm4	approx. 2.0 cm4	approx. 3.0 cm4
Weight	approx. 0.55 kg/m	approx. 1.05 kg/m	approx. 1.15 kg/m
Sensible unsupported span	under 400 mm	under 600 mm	under 1000 mm

What the second slot actually buys

The reason to pay for the wider face is not stiffness alone. It is that a second slot changes the way a light frame goes together.

Two fixing lines on one faceA single-slot 20 x 20 gives one line of fixings, so a plate has to be held by brackets at its corners. Two slots 20 mm apart let a plate or shelf be bolted straight to the member with two rows of T-slot nuts, which removes four brackets per joint and the alignment work that goes with them.

A panel edge without a bracketThe 40 mm face is wide enough to carry a 20 mm slot pitch and still leave material outside the slots, so a panel can be seated on the face and clamped from the slot underneath. That is the usual detail for a light shelf in a display, storage or growing frame.

Stiffness across the 20 mm heightThe second slot is only possible because the face is 40 mm wide, and that width is what raises the section stiffness. A 20 x 40 is roughly three times as stiff as a 20 x 20 about the same axis for about twice the weight, which is the whole economic argument for the rectangular section.

Rule of thumb: if a frame is under about 600 mm between supports and carries panels, lights or sensors rather than machinery, 20 x 40 is usually the cheapest section that will do the job. If it carries a motor, a moving axis or a person, it is not.

Choosing between 20 series and 30 series

Span first, load second Measure the longest unsupported span in the design. Under about 600 mm, 20 x 40 is normally fine for a light load. Between 600 mm and 1 m the section starts to look springy, and past 1 m the 30 series is the sensible starting point even when the load is small, because the limit is stiffness rather than strength.
Check the bolt you actually need 20 series slots take M6 fixings at reduced torque. 30 series takes M6 at full torque and offers an M8 centre bore. If the design calls for a bolt larger than M6, or for a joint that has to survive vibration, the decision has already been made by the fastener.
Count the joints, not the metres A light frame with many joints costs more in brackets and assembly time than in extrusion. Where a design needs more than two fixings per corner, the wider slot pitch and larger brackets of the 30 series usually reduce total cost even though the section is dearer per metre.
Plan the accessory range Both series have a full accessory range, but the 20 series range is smaller and some parts are made only for 30 series and above. Check that the feet, hinges and handles on the parts list exist in 20 series before committing to the light section.

How it is fixed and finished

The two slots take standard T-slot nuts in M6. Corners are usually made with a small angle bracket or a butt connector where the joint is hidden inside the section. Light frames are often stood on levelling feet or small base plates, and panels are held with panel mounting blocks rather than drilled through the face. The slot is closed with cover strip where the frame is on show, which also stops dust collecting in the groove.

Finish matters more on a light frame than on a machine base, because these frames are usually visible. We supply mill finish, clear anodised and black anodised. On a light section the anodic layer is a larger fraction of the wall thickness than on a heavy one, so specify the class at the enquiry stage wherever a nut has to slide freely in the slot.

Typical light-duty work: a vertical growing rack and a small bench frame, both built from 20 x 40 two-slot section.

Frequently asked questions

Can a 20 x 40 profile carry a shelf or a panel?

Yes. Two slots on a 20 mm pitch let a shelf or panel be bolted to the face with two rows of T-slot nuts, which is the main reason to choose this section over a 20 x 20. Keep the shelf span under about 600 mm and support it at both ends.

What is the difference between 20 x 40 two-slot and 20 x 20 single-slot?

The 20 x 40 has a 40 mm wide face with two slots instead of one, roughly three times the stiffness about the same axis and about twice the weight. It also uses M6 fixings with a O 5 mm centre bore instead of the M5 fixings typical of a 20 x 20.

When should I move up to the 30 series?

When the unsupported span passes about 600 mm, when the design needs a bolt larger than M6, when a joint has to survive vibration, or when the accessory on the parts list is only made for 30 series and above. Change the section rather than the wall thickness.

How much does the 20 x 40 profile weigh and what lengths do you supply?

About 1.05 kg/m on a 1.8 mm wall, so a 6 m length is around 6.3 kg. We supply 6 m stock and cut to drawing to plus or minus 0.5 mm, deburred and bagged by assembly.

Can you supply it cut, tapped and anodised to a drawing?

Yes. We cut to length, tap the centre bore and slot ends, drill and counterbore for brackets, and supply mill, clear anodised or black anodised. Send DWG, DXF, STEP or PDF and we quote from the drawing.

Send the frame layout, get a section recommendation and a price

Tell us the longest span, what the frame carries and how many joints per corner. We will confirm whether 20 x 40 is enough or whether the design should move to the 30 series, then quote the section, the machining and FOB pricing, cut and bagged by assembly.

Request a Quote