Joining Plate PG40-4080

OEM / ODM Available Free Sample Available ISO 9001:2015 ISO 14001 RoHS REACH

Transition joining plate that joins a 40 mm member to an 80 mm member at 90°, letting a frame mix a light rail with a heavy leg or spine.

Wholesale Price $0.95 - $4.80 / pc per pc

Material	Die-cast aluminium ADC12 or machined 6063-T5
Alloy Grade	ADC12 die-cast or 6063-T5
Temper	custom
Section Size	40 mm member to 80 mm member
Slot	8 mm slot; 3 + 3 M8 T-nuts
Length	Plate 120 x 120 x 40 mm
Tolerance	±0.25 mm on bolt slot positions
Surface	Anodised or powder coated
MOQ	300
Lead Time	20-30 days after deposit
Loading Port	Shanghai / Ningbo
Supply Ability	60,000 pcs per month
Payment Terms	T/T 30% deposit + 70% before shipment \| L/C at sight
Trade Terms	FOB \| CIF \| EXW
Certifications	ISO 9001:2015 \| ISO 14001 \| RoHS \| REACH

Request a Quote Reply within 24 hours

Joining plates · Mixed sections

This plate joins a 40 mm member to an 80 mm member at 90°. It exists because good frames are not built from one profile size: the legs and the main spine carry the load and are heavy, while the rails, dividers and panel supports carry almost nothing and are light. Using 80 series everywhere wastes material and weight; using 40 series everywhere makes the frame flexible. The transition plate lets the two coexist.

The engineering question with a mixed-section joint is alignment. A 40 mm member and an 80 mm member have different widths, so the joint is asymmetric and the plate has to decide where the light member sits relative to the heavy one — flush with one face, or centred. That choice affects both the appearance of the frame and how the load travels through the joint.

Where a mixed-section frame is the right design

Heavy spine, light railsAn 80 × 80 spine or 40 × 80 leg carrying the structure, with 40 × 40 rails spanning between them. The usual arrangement on a machine frame.

Heavy legs, light shelving80 mm legs with 40 mm shelf rails, so the legs take the load and the shelves stay light and easy to reposition.

Reinforced baseA 40 series frame with 80 series base members, so the frame is light above and stiff at the floor.

Stepped framesA frame that steps in section at a known height, used where the lower part is enclosed and the upper part is open.

The alignment decision

Alignment	Effect	Used when
Flush with the outer face	Light member sits flush with one side of the heavy member	Panels or cladding run on that face
Centred on the heavy member	Light member is centred, leaving an equal step each side	Symmetrical appearance required
Offset to the slot	Light member aligned so its slot lines up with a slot on the heavy member	Cable or a long accessory runs across the joint
Stepped	Light member set back deliberately	Panels of different thickness on each face

The plate carries the offset as a moment. Because the joint is asymmetric, the load path through it is not straight. A plate that suits a flush alignment may not suit a centred one, because the bolt positions change relative to the load line.
Two plates are still the rule. As with any structural corner, a plate on each visible face gives the stiffness. On a mixed-section corner the second plate is often more important, because the offset makes the joint less naturally stiff.
The slots must line up if the joint carries cable. Where a cable runs through the joint, the plate has to be positioned so the slot of the light member meets the slot of the heavy member. That is a drawing decision, not a site decision.

Why the 80 mm leg is worth its weight

An 80 × 80 profile has roughly eight times the second moment of area of a 40 × 40, so for the same span it deflects about an eighth as much. That is why a heavy leg or spine in 80 series transforms the stiffness of a frame at a fraction of the weight that an all-80 frame would cost.

The trade is that the 80 mm member is heavier and its slot is further from the member face, so accessories on it need a longer bolt. The transition plate is what makes the mix practical, and the frame ends up both stiffer and lighter than an all-40 design — which is why the arrangement is standard on machine frames.

Practical point: decide the alignment at the drawing stage and put it on the drawing. A mixed-section joint that is aligned differently at different corners of the same frame looks like a mistake and often is one — it usually means a panel will not sit flat.

Frequently asked questions

Can the plate join 40 × 40 to 40 × 80?

Yes, provided the 40 × 80 member is being used as the heavy member. Confirm the section orientation on the drawing, because a 40 × 80 can present either a 40 mm or an 80 mm face to the joint.

Where should the light member be aligned?

It depends on the panels. Flush with the face that carries the cladding is the usual answer; centred is used where the frame is seen from both sides and symmetry matters.

Do I need two plates at a mixed-section corner?

Yes, and often more than at a same-section corner, because the offset makes the joint less naturally stiff.

Will the plate fit a 40 × 80 leg and a 40 × 40 rail?

Yes. That is the most common use of this plate — a 40 × 80 leg carrying 40 × 40 rails.

Can the plate be made in a custom offset?

Yes. The bolt positions can be set to whatever alignment the frame needs, quoted from the drawing.

Send the two sections and the alignment you want

Tell us the two profiles and how the light member should sit against the heavy one. We will confirm the plate, the bolt pattern and the alignment, and return FOB pricing within one working day.

Request a Quote