What rivet to use to join aluminium?

[Chris TickTockParticipant @christicktock]

Hi Guys,

I need to join a piece of 1/4 inch thick aluminium to a 1/8th thick piece. I have no special welder. Also I do not want to risk bonding the pieces together as if it fails as it will be used on my mill it could be a hazard. Therefore solid rivets are my route, blots being ugly. I have gone for the solid countersunk type for looks. However what material in terms of the rivets is acceptable. The pieces are just a shield with no stress on them.

is steel, aluminium or brass my best bet?

I have read galvanic reaction( corrosion) will / could occur with steel but is this applicable to brass and in any case is this more of a theoretical consideration than practical.

Chris

[Chris TickTockParticipant @christicktock]

[JasonBModerator @jasonb]

Aluminium rivits will be easiest and as you don't like looking at them if done well and draw filed flush you should not even be able to see the rivits.

Depending on how close to the edge of the work the holes are using steel or brass may distort the work making it bulge at the sides so stick with aluminium rivits, copper as second choice.

Edited By JasonB on 11/09/2020 18:36:49

[SillyOldDufferModerator @sillyoldduffer]

All my early metal work was chassis bashing, which is bending Aluminium plate and fixing it together to make a support and box to hold electronic circuits, amateur radio in my case. In the good old days, shape a box and front panel out of sheet, bore holes for meters, controls, and valve bases (tubes in USA), and join the whole lot together. The quickest and cheapest fasteners are Aluminium pop-rivets, available many forms and sizes.

Drill hole to suit rivet, insert, and pull the nail out with a rivet gun.

Pop rivets are functional rather than good looking and can be extra ugly untidy at the back. Don't expect to win prizes for craftsmanship. A major advantage is they can be placed from one side, which is important when access is limited. They can be removed by drilling the head off, easy because the hole guides the drill.

Making chassis I mixed steel and brass bolts and Aluminium without corrosion. BUT radio equipment is used indoors and kept dry – no condensation. You will get corrosion if there's any damp about, which is likely in a workshop. In my limited experience Steel goes rusty without damaging Aluminium, but brass and aluminium can corrode badly where they meet. Best not to mix metals far apart in the electrochemical series if it can be avoided. Vital not to mix them in aircraft and boats!

I'd use aluminium pop rivets on an aluminium tool.

Dave

[EmgeeParticipant @emgee]

Aluminium c/s both sides would be my choice, especially if you want it to be invisable fixing.

Emgee

[ChrisBParticipant @chrisb35596]

Attaching 1/4" to 1/8" sheet I would drill and thread the 1/4" piece and drill and countersink the 1/8" piece. Then use shearhead fasteners. Then you can take on and off at will.

[Mike PooleParticipant @mikepoole82104]

I would go with aluminium rivets but have you considered one of the low temperature methods like lumiweld?

Mike

[Speedy Builder5Participant @speedybuilder5]

Chris – Surely you must have thought how aeroplanes were stuck together before we started bonding sheets together. When I was an apprentice, they used so many rivets, that the floor below the jigs that held the wing ribs, spars etc during the manufacture of same were littered with rivets – probably 50Kg or more before they were finished, and all then chucked in the bin.

Regarding aluminium rivets, there are several different material specs from pure Al being the softest (easiest to set) through to special Al alloys that have to be heat treated immediately before use.

[Chris TickTockParticipant @christicktock]

Thanks for posting everyone . So it's a choice between threading or aluminium rivets.

Regards to all

Chris

[Bo’sunParticipant @bosun58570]

I've heard that galvanic corrosion can be quite a problem between aluminium and copper. A friend of mine built an aluminium boat, but didn't consider the consequences of dropping pieces of copper wire into the hull/bilge while installing the electrics.

[jann westParticipant @jannwest71382]

Related to the question … re: the galvanic issue – when using (stainless) steel bolts or rivets in aluminium in a scenario where galvanic corrosion is an environmental certainty (e.g. attaching anything to an aluminium mast on an ocean-going yacht) one typically liberally applies a special paste (grease) on all mating surfaces to inhibit the galvanic corrosion … I recall it was called the "yellow paste" but google seems to think it is sold under the name "duralac"

[HopperParticipant @hopper]

It's a swarf guard on a mini milling machine, not a plane or a boat. Bang in a couple of pop rivets of whatever material comes out of the box first and carry on. If you want to get fancy, use stainless steel pop rivets for maximum strength in a vibration prone environment.

Boats have their own special corrosion problems due to salt water etc and planes, well things get a bit more critical again there. Nothing to worry about in the home workshop though.

Even aircraft aluminium alloy will eventually succumb to galvanic corrosion with itself if left in a salty water environment for long enough as the alloying metals such as zinc, copper, tin, lead, magnesium etc react with the aluminium parent metal. The alloy turns to white dust and disintegrates. Old WW2 aircraft left on the beaches where they crashed in remote tropical coastal areas of Northern Australia do this. But it takes 50 years or more in a very hostile environment, not your workshop.

Edited By Hopper on 12/09/2020 12:50:56

[Dave Smith 14Participant @davesmith14]

Google is correct, the yellow paste is called Duralac. Used extensively in Aerospace.

[Howard LewisParticipant @howardlewis46836]

If it merely a swarf guard subject to minimal stress, pop rivets will be fine. But you will need to find some long ones to pass through the 1/8" plate (presumed to be the visible part, to expand into the 1/4 behind.

With those thicknesses, I would feel inclined to use Countersunk screws, tapped into the 1/4 plate.

A neatly spaced row of holes will look quite neat.

And after a while with scratches, dings and splashes will it really matter?

You are not planning to enter your shop or machines in any concours d'elegance competitions are you?

Howard

[Chris TickTockParticipant @christicktock]

Posted by Howard Lewis on 12/09/2020 13:24:24:

And after a while with scratches, dings and splashes will it really matter?

Howard

Howard,

Great minds think alike, that is what my Decorating business prepares our customers with before we start (Ha Ha!)

Chris

[Tim StevensParticipant @timstevens64731]

Aluminium does not rust,

It crumbles to a greyish dust,

And most of that which you can see

Consists of Al 2 O 3

A popular ditty at the Alcan factory when I were a lad.

Cheers, Tim

[Howard LewisParticipant @howardlewis46836]

In a reasonably dry workshop environment, steel fasteners are unlikely to produce much corrosion on Aluminium, especially if greased before fitting to provide, at least, some insulation.

If you want to see electrolytic corrosion, put copper and aluminium in contact in a saline environment!

You don't use Copper/Asbestos joints between a Cast Iron cylinder head and an Aluminium "water" cooled exhaust manifold in a marine environment!

Howard

[ChrisBParticipant @chrisb35596]

Posted by Tim Stevens on 13/09/2020 18:16:15:

Aluminium does not rust,

It crumbles to a greyish dust,

And most of that which you can see

Consists of Al 2 O 3

A popular ditty at the Alcan factory when I were a lad.

Cheers, Tim

Maybe rust is not the correct term as it's normally a term reserved for Iron and its alloys, but exposed aluminium alloys surely do corrode, even when maximum protection is afforded. On aircraft I have seen fittings, seat tracks and skin panels exfoliated like puff pastry…even though the aluminium was etched, primed, topcoated and a layer of dinitrol applied…Sometimes I suspect the material is defective.

Our friend Christicktock should have none of these problems tho.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by ChrisB on 14/09/2020 08:27:36:

 

.

On aircraft I have seen fittings, seat tracks and skin panels exfoliated like puff pastry…

.

Mercury spillage can do serious damage to aircraft

MichaelG.

.

PostScript: ___ I’ve been away from the industry for years … but have just found this fairly recent document:

https://publicapps.caa.co.uk/docs/33/CAP1570_Corrosion.pdf   See para 6.2 

Edited By Michael Gilligan on 14/09/2020 08:47:34

[Lee RogersParticipant @leerogers95060]

A few soft solid rivets and if you want belt and braces bond it as well. The bonding + rivets method would allow the use of less rivets and resist peel loads .

[Bill PudneyParticipant @billpudney37759]

During my apprenticeship, a helicopter fell into the sea, well the Solent actually. It couldn't be recovered for almost 24 hours. When the poor thing was plonked onto the slipway, most of the fuselage skinning had gone away and there were large holes in the main gearbox that you could put a clenched fist through. These were all magnesium alloys, but it shows how quickly corrosion can happen.

The company built hovercraft, which operate in a VERY moist salt water spray environment. During assembly of sheet metal bits, there were three different types of jointing compound, red, yellow and brown, at this distance I cannot remember which one was used where (one was used on painted metal, one on bare metal etc), but they were all intended to keep moisture out of joints. If the wrong one was used the inspectors would go ballistic.

cheers

Bill

[GeorgineerParticipant @georgineer]

Posted by Tim Stevens on 13/09/2020 18:16:15:

Aluminium does not rust,

It crumbles to a greyish dust,

And most of that which you can see

Consists of Al 2 O 3

A popular ditty at the Alcan factory when I were a lad.

Cheers, Tim

Interesting. I've always known it as "white rust".

George B.

[Ron ColvinParticipant @roncolvin83430]

Posted by Bill Pudney on 14/09/2020 08:56:15:

During my apprenticeship, a helicopter fell into the sea, well the Solent actually. It couldn't be recovered for almost 24 hours. When the poor thing was plonked onto the slipway, most of the fuselage skinning had gone away and there were large holes in the main gearbox that you could put a clenched fist through. These were all magnesium alloys, but it shows how quickly corrosion can happen.

The company built hovercraft, which operate in a VERY moist salt water spray environment. During assembly of sheet metal bits, there were three different types of jointing compound, red, yellow and brown, at this distance I cannot remember which one was used where (one was used on painted metal, one on bare metal etc), but they were all intended to keep moisture out of joints. If the wrong one was used the inspectors would go ballistic.

cheers

Bill

Maybe they should have built the hovercraft out of the jointing compounds.

[J HancockParticipant @jhancock95746]

The reply of Howard Lewis is particularly relevant to Rootes Group engines where the cast iron block had a steel/asbestos/ copper gasket interposed between the aluminium head , then on to a brass radiator to create a diabolical battery .

The inevitable corrosion wrecked every cylinder head and iron migration from the block left unsupported graphite patches to finish it off !

[Author]

Posts