YES!, patb2009, I TOTALLY AGREE! That's one of the MAIN reasons why Americans (the U.S., in particular) feed & support about ONE HALF the free world, and probably one quarter the "not-so-free" world, INCLUDING our avowed enemies!!!!!!!!
I said "Americans", because like it or not, Canadians & Mexicans ARE also "Americans", since we all reside in countries defined by the continent of North America!
Well, everyone is grumbling about the dissimilar metals issue of aluminum sockets with brass rivets.
Has no one realized that this results in an aluminum-to-aluminum contact between the socket shell and lamp? Changing to a brass socket shell would provide a very large area of dissimilar contact between the threaded aluminum socket and the threaded aluminum bulb base, likely resulting in seizure. It's dangerous to twist a bulb off its base and more dangerous to remove the base from the socket--ideally with safety goggles and power off using pliers or potato. But how many homeowners will do it with bare hands (lacerated fingertips) and no goggles?
On that basis the aluminum socket is safer than a brass one.
Jim, thanks for the current information, or at least fairly current. I knew that it all had to do with cost, nothing else drives choices of materials for a lot of stuff today. Probably if poor quality steelm were cheaper they would be made of that.
The very cheapest quality of aluminum for castings is unique in that it develops rust spots, since it includes ireon and steel fragments.
JIm, my guess is that in the line of really cheap alloys that the aluminum alloy used for light sockets is quite cheap, while the copper that draws nicely costs more. Possibly not much more, but perhaps a penny a pound more. Enough to cause quality to be sacrificed for price.
Meanwhile on the other topic of 'Draw-capable" alloys, you suggested that Aluminum is easier to deep-draw. In my experience working with draw dies, two alloys called NickelSilver CDA770 and CDA735 were most often chosen because of their superior malleable stretch during the draw. (These materials are primarily Cu base, so the name NiAg is misleading).
I remember once trying an aluminum sheet in an existing die designed for CDA770 (as a cost-saving idea) and the Aluminum test part split open. Point being, I concluded copper was a better draw stock than aluminum. Maybe the rolled threads for the light socket base helped provide better 'draw' integrity, in these aluminum sockets.
Of course, you are right –I suffered a lapse there, thinking for a moment that brass was a natural element. In my mind, I had set Bronze aside as an Alloy, and that (incorrect thought) left Brass remaining as an element. Had to go back and look at the Periodic Table and a Bronze/Brass Alloy sheet I have. Thanks for the correction.
Brass and copper have very similar electrogalvanic potentials because brass is mostly copper. So of course.
Now as for why aluminum gets used so much in sockets, it is a fact that aside from costing a lot less, aluminum is easier to deep draw, and all of the threaded parts are deep drawn. So those are the main reasons aluminum is used. The copper rivets are used because aluminum rivets would fail very soon in that environment, while a copper rivet can hold it's preload tension a lot longer. And there is not a fire hazard of any sort when the connection fails, contrary to some assertions. And I have seen and replaced a lot of those sockets over the past ten years or so. It seems that the quality from China does not match the quality from where they came from before. BUT really poor quality and poor manucaturing processes will always produce poor quality products, which does happen sometimes.
@LarryM: I agree with you. I have rarely had lamp or socket problems as described. However, I do always look for porcelain housings where the application will be bulb down, as in ceiling fans. I have had plastic housings become so brittle, they fall apart when trying to remove the bulb.
I have also made it a habit to lube an aluminum base with WD40 before insertion as it makes it easier to remove when they have burned out.
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