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Fred_M
01-18-2007, 07:51 PM
What is "Pot Metal" ? How does the thermal expansion and contraction
compare to CR1018? I am thinking about making a heavy base for my
Sherline ( I can hear the laughter from here) lathe.

Todd Tolhurst
01-18-2007, 08:01 PM
Pot metal is a generic term for a variety of zinc alloys, such as the various ZAMAK alloys. Here's some data (http://www.eazall.com/diecastalloys.aspx#Physical%20Properties) that might be useful. Looks like the coefficient of thermal expansion is around double that of 1018.

I'd never laugh at your Sherline. I love mine. :)

Fred_M
01-18-2007, 10:58 PM
Thanks for the info Todd. I want to make a metal base to add weight. The guys at Sherline said that the existing bases on their lathes were "pot metal".
I tested with a magnet and didn't get any reaction. Thats's why I asked them. The Sherline stuff was a great thing to learn on. With a small fractional
HP motor, mistakes are not as dangerious as the big machines. Great for small work though.

Evan
01-18-2007, 11:41 PM
Use lead. I bought 75 lbs of lead for $10 from a local tire shop in the form of wheel weights last summer. I melted it and cast it to make a counterweight for my mill. It would be easy to make a base for the Sherline and the coefficient of expansion is in the same range as zinc alloys.

Come to think of it, that's a really good idea. I think I'll make a base for my Unimat from lead. The damping is unbeatable. I still have about 30 lbs left. A cookie pan would be perfect for casting in.