Hi, Back in December I inquired about making a ball vise. I have been practicing some simpler machining since, and now would like to begin.
I never did have any luck finding 7-10" diameter steel balls or even solid rod at scrap yards.
I can buy 6" rod stock from the campus machine shop for ~$60, or $1.10/lb I believe it was (although my calculator is predicting that it should be $48, so it might have been more...), and machine it into one hemisphere and one clipped-off cone shape. The hemisphere is doable; I have access to a CNC lathe. Off campus, inquiring about 8" diameter rod stock, they wanted $1.75/lb!
Alternatively, I can cast. I asked a local club, and they'll help me cast it for $1.20/lb if I provide the steel. I can find random scrap steel for $.10/lb. This at first had great appeal when I learned of the low cost of scrap steel, but it makes me recoil some to think that I'll end up paying more per pound because of casting costs! AND, coming out of the cupola, it will be cast iron, which while quite functional, is inferior to steel for this application. The two benefits of this would be that a sphere is 2/3 the volume of the smallest cylinder that will contain that sphere, so even though it's $1.30/lb and not $1.10/lb, it costs $.23/lb less to cast in a sphere than to purchase a solid cylinder and machine off 1/3 of its weight in making it a sphere. Also, while I still want to program the lathe to machine a sphere, it will have to machine off far less material, saving not an insignificant amount of work.
What do you advise? Cast an iron sphere, or machine from a solid steel cylinder, assuming the former to cost 23cents/lb less? I want a
100-lb vise (trust that I do intend to make a 4.5" vise from all scrap first, before investing in this), so this is expensive for me :-( Is it possible that, if I shop around, I may be able to have it cast for less than the $1.20/lb quoted me, or is that a bargain...?thanks! -Bernard Arnest