Muckite

I never heard that term, and I've got the idea that the boxes are made from some kind of aluminium alloy

The entrapped air probably degrades the metal enough to explain the term "muckite".

At Cabridge Instruments, which was a high class machine shop long before they got into electronics, nobody ever used the term, but they did understand the materials they were working with.

If you really feel like suffering, try finish-machining an aluminum sand casting. One of those rapid-tool-change collets helps a lot.

John

Nope. New one on me.

But probably grossly overstaffed.

Graham

How about doing it by hand?

Ya, made that with my foundry.

Tim

Yep. That's the stuff I was brought up to know it as. (or 'shitite' as I prefer)

Hmmm! nifty job :-)

Yes, Muckite was the standard word for that Zinc alloy casting metal. I used Muckite diecast boxes by the bucketload. The early types had a fearsome taper on them though, and there was one mfr who used muckite with a lead? content (Eddystone?) which had a tendency to snatch the drill if you were not careful.

"martin griffith"

But a Kiwi colleague would often refer to cheap, brown PCBs as being made from "compressed dog turds".

Diecast boxes vary greatly. Some are light as a feather, so must be mostly Zinc and Aluminium - while others are heavy and so must contain a large percentage of lead in the "muck".

IME, the light ones are tricky to machine largish holes in for XLRs etc.

I find a " step drill" ( made by G & J Hall Ltd in the UK) to be invaluable when dealing with them.

....... Phil

Those work well.

I've never had any trouble using Q-Max punches on them though ( for holes up to

Graham

The DI boxes I make need a 19 mm hole in the 26mm side of a small plastic coated box with internal ribbing.

A 20mm chassis punch causes serious crumbling or even breaks the side open.

OTOH, a Hall step drill goes through it like a hot knife through butter.

...... Phil

I helped by leaving....

martin

FWIW, I've heard it called "pot metal", but it was just from some guy who has about as much credibility as a typical USENET poster. ;-P

Cheers! Rich

That is a general term for cheap alloys -- I think it means metal from the melting pot, where the blacksmith melts a mixture of all sorts of stuff. (In particular, steel with copper in it is not very strong.)

My further recollection is that "pot metal" alloys tend to be brittle and crumbly when broken. They aren't seen much any more; since about 1960, plastics have been strong enough to take their place.

Won't the sound be "grainy" and "bright"?

John

The metal used in diecast boxes certainly crumbles when you use a Q-max punch on it, at least the bit you're removing does.

Graham

martin griffith scrobe on the papyrus:

I worked in Telerecording and P&ID between '69 and '74 and our mechanical guys usually applied the term to the charred paxolin panels that the valve amplifiers were built on. I guess they probably weren't charred when the equipment was new, but most of it was of mid '50's vintage.

Ironically, ZA-27 is about as strong as gray cast iron. (That's 27% Zn, 1% Cu, 0.05% or so Mg, balance Al, as I recall.)

The real problems are, die castings are made thin to reduce expense and weight; the die casting process inherently leaves porosity, since the air isn't evacuted as the metal is injected; and stress cracking problems with the zinc-aluminum series alloys leading to such faliures as things falling to dust as some have mentioned.

Tim

- Going purely by the name, it could be "Zamak" or pot metal, mainly zinc plus assorted floor sweepings.

Yep, but aka "Pot metal" "Shit metal" and "Shineyshit" All are Zn-Al casting alloys, also widely used in car bits and pieces (carburetter bodies is one example)

See

It's eay to work, but hardly resistant to impact. Many woods are stronger!

Barry Lennox