Where the
world gathers for metal finishing
Q&As since 1989


-----

Polishing Invar for mirrors

1999

Dear Sirs,

I am going to make a concave mirror from "invar"(36% Ni and 54% Fe) with the following specifications:

Diameter: 20 inches, Thickness: 1.62 inches, Radius of curvature: 275.6 inches, Roughness average: 1 microinch

I haven't performed "grinding" and "polishing" on the object mentioned above with the said dimensions and accuracy. Also I don't have access to polishing machines and have perform the polish by hand.

I would really appreciate it if you could tell me how to polish and grind the object and what kind of material(s) I must use.

Moreover, could you please let me have an estimation of the cost of your proposed method for grinding and polishing separately.

Thank you in advance.

Regards

Iman

P.S: The starting roughness is 1 micron.

Iman Azarian Borojeni
Shiraz university Iran

You might want to consider having the part plated with high phosphorous electroless nickel and then have the critical surface diamond turned. This method produces a flawless finish with very precise dimensional accuracy with surface finishes attainable down to the angstrom level.

Rick Richardson, MSF
Dayton, Ohio
1999