Joining Plate PG40-8080

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

Heavy joining plate for two 80 mm profiles at 90°, a structural corner joint for machine bases, gantries and heavy frames where the joint carries the load.

Wholesale Price $4.20 - $18.50 / pc per pc

Material	Machined aluminium 6063-T5 or steel
Alloy Grade	6063-T5 or S355 steel
Temper	custom
Section Size	80 x 80 mm profiles at 90 degrees
Slot	8 mm slot; 4 + 4 M8 or M10 T-nuts
Length	Plate 160 x 160 x 40 mm
Tolerance	±0.25 mm on bolt slot positions
Surface	Anodised, powder coated or zinc plated
MOQ	100
Lead Time	20-30 days after deposit
Loading Port	Shanghai / Ningbo
Supply Ability	20,000 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

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Joining plates · Heavy structure

This plate joins two 80 mm profiles at 90° on a frame where the joint is a structural element rather than a locator. On a light frame a corner plate holds two members in position and the members carry the load. On a heavy frame — a machine base, a gantry, a press frame — the joint itself is in the load path and has to transmit the full bending moment and shear of the connection.

The design of the joint changes at that point. A single plate is no longer enough, the bolt count matters, and the question of whether to bolt or weld the joint becomes real. The 8080 plate is the bolted answer to a joint that would once have been welded: it keeps the frame demountable and transportable while giving the joint enough capacity to be trusted.

When a joint stops being a locator and becomes structure

Frame	Joint role	Typical plate	Bolt count
Light enclosure	Locates the members	Standard L	2 + 2
Machine frame	Carries member weight	Heavy L	3 + 3
Machine base	Carries the machine and a moment	8080 heavy	4 + 4
Gantry leg	Carries a bending moment	8080 heavy + brace	4 + 4
Press or forming frame	Carries the process force	Welded or 8080 heavy	4 + 4 or welded

The change is not gradual. Up to a machine frame, the corner is mostly locating and the member is doing the work. On a machine base or a gantry, the corner carries a bending moment that the members alone cannot resolve, and the joint has to transmit it. That is the point at which the plate becomes a structural component and the joint should be designed rather than assumed.

Bolted or welded

Bolted (this plate)The frame stays demountable, transportable and adjustable. No heat distortion, no post-weld straightening, no repainting of a weld. The right answer for almost every machine frame.

WeldedStiffer than a bolted joint for the same material, and it removes the bolt slippage that a heavily loaded friction joint can develop. It also makes the frame a permanent assembly and adds distortion and finishing work.

Bolted plus braceThe practical middle. A heavy plate pair plus a diagonal brace gives most of the stiffness of a welded joint while keeping the frame demountable. The usual answer for a gantry.

Bolted plus bondedA structural adhesive in the joint in addition to the bolts, used where a bolted joint alone is marginal. It raises stiffness without welding, but it makes the joint permanent in practice.

Bolt slip is the failure mode of a bolted heavy joint. A friction joint holds until the load exceeds the friction, then it slips and the frame moves. On a heavy joint the bolts are specified so the friction capacity exceeds the working load with a margin, and the bolts are torqued to the full figure.
Two plates minimum, four on a heavy corner. On an 80 mm corner the plates go on both visible faces, and on a loaded corner they are doubled or a brace is added. The plate area is what resists the rotation.
The members have to be up to it. A heavy plate on a light member just transfers the problem: the member deflects or the slot deforms. On a structural joint, the member section and the plate are designed together.

Establish the joint load The bending moment and the shear at the joint, from the frame analysis. On a machine base or a gantry this is a real number, not a rule of thumb.
Check the member section Confirm the 80 mm member can carry the moment. A heavy plate cannot compensate for a member that is too light for the span.
Size the plate and the bolt count The plate area resists the rotation; the bolts resist the shear. On a heavy corner the usual figure is four bolts per leg and a plate on each face.
Torque to the full figure A friction joint depends entirely on the torque. Use a calibrated wrench and record the figures — on a structural joint this is a quality record, not a formality.
Re-check after first load Bolted heavy joints bed in under the first full load. Re-torque after the frame has carried its working load for a shift, then at the first service interval.

Practical point: on a frame where the corner moment is significant, send us the load case and we will check the joint — plate size, bolt count, torque and whether a brace is needed. It is a short calculation and it is much cheaper than discovering a slipping joint on a commissioned machine.

Frequently asked questions

Is a bolted joint as stiff as a welded one?

Not quite — a welded joint is stiffer for the same material. But a bolted joint with a heavy plate pair and a brace comes close, and it keeps the frame demountable, which matters for transport and for machines that are modified in service.

How many bolts does a heavy 80 mm corner need?

Four per leg is the usual figure for a loaded corner, with a plate on each visible face. The count is set by the shear at the joint, not by the plate.

What torque should the bolts be?

Around 40 Nm for an M8 T-nut in an 80 series slot, but confirm against the profile supplier’s data. A friction joint is only as good as its torque, so use a calibrated wrench.

Can the joint slip?

It can if it is under-torqued or overloaded. A friction joint holds until the load exceeds the friction, so the bolts are specified with a margin and torqued fully.

Can the plate be welded instead?

Aluminium 6063 can be welded, but welding a heat-treatable alloy reduces its strength in the heat-affected zone. On a structural joint that has to be welded, the design should account for the reduced properties near the weld.

Send the load case and we will check the joint

Tell us the frame, the load on the corner and the span. We will check the plate, the bolt count, the torque and whether a brace is needed, and return FOB pricing within one working day.

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Joining Plate PG40-8080

When a joint stops being a locator and becomes structure

Bolted or welded

Frequently asked questions

Send the load case and we will check the joint

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