On Monday, February 3, 2014 8:08:11 PM UTC-5, whit3rd wrote:
On Friday, January 31, 2014 5:50:22 AM UTC-8, wrote:



I'd like to make some little radiation shields for use at 77K (liquid nitrogen)



So cylindrical type cups.. maybe 2" diameter and 3-4" long. I've only heard about spinning aluminum, but can you also spin other metals something like TeCu (tellurium copper)

Yes, of course you can spin other metals; for a heatshield, though, Al is the right stuff.

OK why do you say Al is the right stuff? I realize that most of the radiation sheilds I've seen are Al. But what is wrong with nickel plated copper?
Copper has a little more heat capacity (per volume), but also a greater thermal conductivity. If you calculate a time constant to get heat out of a cubic centimeter of material (at 300K) you get something like 1 second for Al and a bit less for copper (0.85 seconds) Basically the same.

Thanks for the rest of you anwer.

George h.

Does the spinning work harden the metal?



Yes; that's one good reason to do it. Gongs and cymbals for instance, are almost always spun.



Can it be annealed afterword?



Yes, or between operations in multistep spinning operations.



How thin a wall/ bottom can you make?



Only limit is if the metal tears (and polished tools and/or heavy greases are recommended

to minimize this). It's recommended to spin alternately from center out and from rim in,

to get a uniform thickness result.



If you care for a less dynamic approach, you can also consider cold-drawing of

aluminum; machine an internal die and press a metal sheet against a block of rubber

(urethane? neoprene? silicone?). It'll take several steps and annealing between draws.