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How do you attach grounds point to aluminium?

7/24/2000 12:06 PM
How do you attach grounds point to aluminium?
Are mechanical grounds reliable? can you solder to aluminium? I don't seem to be able to.  
Any help greatfully apreciated. JD
7/24/2000 1:30 PM

No, you can't solder to aluminum, at least not without special equipment. What I do is to drill holes where I want the star grounds to go, and I use a brass bolt into the chassis with a nut and lock washer on the inside. Then you can solder to the bolt anything you wish to attach to it.  
7/25/2000 12:00 AM
I prefer a solder connection any day. Here's what I'm doing with my amps.  
Go to the local metals wholesaler and pick up a length "Flat" copper, it's surpisingly cheap. I worked it out to about $.75 per amp. I use 1" x .125" x 12'. I cut a piece about 4" long, drill a hole in each end, bolt it to the chassis and star ground everything. I worked out the layout inside so that I use the O/T or the choke bolts to secure the copper.  
This works for me, hope this helps.  
7/25/2000 12:57 AM

The industry standard for reliable grounding to aluminum chassis is with a screw through the chassis, a star washer next to the chassis, the grounding terminal attached to the wire, another star washer, and then a nut. The star washer next the chassis bites into the chassis and forms many point-contact places where the aluminum oxide layer has been scraped or punched through, and the spring pressure keeps air out of those places, so you get gas-tight contact points. The top star is to keep the pressure on when the nut is tightened down.  
There is a variant of brazing you can do to aluminum with a propane torch and some special "solder", but it's not easy to get right.
7/25/2000 3:22 AM
I don't understand why anyone would make a mechanical connection that will oxidize over time. The "spring pressure" does not creat a vacuum so oxidation will occur, eventually.  
R.G., I greatly appreciate/respect your input here but,  
just because it's the "industry standard" doesn't make it the best way, it just makes it the easiest and cheapest way. IMHO.
7/25/2000 3:42 AM
Peter S

Forget using the aluminum as a conductor. I just built my first aluminum chassis amp after 20+ years of building with chrome plated steel. I ran a separate ground wire(20ga 600 volt TEW) from EACH individual ground to a single star ground point next to the power tranny. I bolted the star ground to the chassis just to use the chassis as shielding. This amp has no audible hum and I don't have to worry about grounds giving me headaches later on.  
Peter S
7/25/2000 9:06 PM
Matthew Springer
Star grounding in Al chassis
The local "ground collection points": are these isolated from the chassis electricly (I assume so)?  
If so, how? Using turret strips or what?  
-just curious
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