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Aluminium Box Joint

Aluminium Box Joint

Aluminium Box Joint


I need to produce some high spec cabinets with a box joint on the ends of large sheets of 10mm thick aluminium 6082 T6 tooling plate , the sheet sizes range from 400 w x 2500mm long to 800 w x 3000mm long . I have attached a picture of a sample cabinet we produced which was milled on a Bridgeport type bed mill layed flat ( as the sheet is too wide to stand up ) with 90 degree head to produce the slots .The client loves what we have done & we now have to produce loads of cabinets so we need a better & quicker way to produce these joints. The joints themselves need to be very precise i.e maximum of 0.1 mm clearance in the fit , I believe the sample we made was 0.05mm clearance & we used grooved pins inserted to give the actual strength in the joint which is we would look to do in the new cabinets as well.

I was wondering if there was either a better technique or more suitable machine to do these on ( maybe even an aluminium extrusion processing machine ?).All faces need to be brushed finish which we can get the flat faces done by a sub-contractor after they are notched but the ends & sides would need to be done by ourselves prior to sending to polishers. For this reason I have steered away from waterjet as it would leave a fluffy edge & I would be worried that the box joint fix might not be accurate enough.

Any help would be greatly appreciated

RE: Aluminium Box Joint

The only reason for a box joint in metal is cosmetic, so make a practical joint by welding and then scribe and etch a pattern to make it look like a box joint.

RE: Aluminium Box Joint

Ideally, these would be stacked up as much as the machine allows, and sent to a horizontal mill or a wire EDM.

If you're seeing sufficient quantities, it may pay off to have it outsourced to a machine shop with a horizontal mill that run a stack of them at a time. It should be a reasonably cheap endeavor for any respectable shop.

I would steer away from waterjet because any kerf variance due to the 'v-shaped cut' of a laser/waterjet/torch would be very quickly apparent on the joints. It won't make /perfectly/ square cuts.

NX8.0, Solidworks 2014, AutoCAD, Enovia V5

RE: Aluminium Box Joint

Compositepro - Unfortunately our customer will not accept anything less than what we did for the sample so we can not get away with etching or scribing etc , good idea though.

JNieman - I will look into local horizontal millers or EDM process . As some of the panels have slots , holes recesses in them on the flat faces to suit shelves etc , in my mind its like you need a big cnc Router/ Bridge miller to do all this . But as far as I can see this type of machine will not be able to do the end notches etc , so this is where I become unstuck . Maybe its not possible to do all processes on the one machine ?

I will be able to upload a cad file soon for clarity on the detail.

RE: Aluminium Box Joint

The 3meter length is pretty much the only reason it'll because hard to find a single machine to do it all. That's rather large to be able to spin around in a horizontal mill. Additionally, if you want it done all in one machine, you lose the efficiency gains of stacking a bunch together to cut the slots 'all in one step'.

I would just send the part out for quote to shops and see what they quote back - let them handle the process. That's what they're for. There's no reason to expect a part to be done in one setup. There's nothing wrong with doing it in two, either.

Based on what I know, though, with the experience I've had; I would do it in two machines. I would clamp stacks of them together to do the end-notching, and do the slots and pockets with many laid flat on a large tabled vertical mill. That is, unless someone has a horizontal that can swing 3000mm parts and still do end work on them. Anyways, let the shop figure out how to make it.

NX8.0, Solidworks 2014, AutoCAD, Enovia V5

RE: Aluminium Box Joint

Have you thought about broaching the slots? The size of the sheets would not be a problem for that process, just need a larger table to support them. You could cut a single slot at a time or several at once.

RE: Aluminium Box Joint

Or, you can make a template and cut the slots with a router, just as you would for a wooden box joint. See the templates sold for cutting dovetail joints. Regular woodworking bits will work ok on aluminum, with some practice required to keep from overfeeding them, and avoiding the hot chips flying off. You don't need to slow down the router at all; aluminum cuts nicely with woodworking tools.

Mike Halloran
Pembroke Pines, FL, USA

RE: Aluminium Box Joint


hendersdc - I did think about broaching but was concerned about the finish & the slot breaking out , I suppose as long as you make a backing piece this would sort the breaking out problem

MikeHalloran - I will try the routing process , it was something I toyed with as it would be a lot easier to do rather than the setup you would have on the mill.
Watch this space to see how I get on ...

RE: Aluminium Box Joint

Try to get a router bit with spiral flutes.
... or just use a spiral fluted milling cutter.

That will give you a better finish and less impact damage (to your hands, the cutter, and the workpiece) than a straight fluted cutter, and will help clear the chips from the cut.

Mike Halloran
Pembroke Pines, FL, USA

RE: Aluminium Box Joint


actually having these rough cut by water jet then do the final machining as Mike specified might be an option. have the waterjet leave approx. .060 inches stock
then finish it with a router.


RE: Aluminium Box Joint

Use a CNC router to cut the panel. Cut it with the brushed/protected surface downwards on the router table onto a wasteboard so you do not get any burr.
The dovetails will have an internal radius which you can trim out of the corners using Mike Halloran's method. If you use a large enough machine you can throw the whole sheet onto the machine and nest the parts.

You are judged not by what you know, but by what you can do.

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