"PrecisionmachinisT" wrote in message
news:SsqdndCiuYHgtsvMnZ2dnUVZ_uWdnZ2d@scnresearch. com...

"Ed Huntress" wrote in message
news
On Fri, 29 Mar 2013 16:13:03 -0700, "PrecisionmachinisT"
wrote:

--even with single point diamond tooling, surface finish becomes a
big factor when it comes to accurately gaging workpiece diameter..

Keep in mind that master hard-drive disks and the production disks,
back when they were made this way, were single-point turned. No
grinding. We built lathes especially for turning them at Wasino --
and
they were all shipped to Singapore. sob


Still they were nowhere near to a mirror finish.

And those were flat.


Moore Special Tool built special turning machines for making
assymetrical lenses for the Defense Dept. They were all single-point
turned, although some of them (for shorter wavelengths of light)
were
polished.


I've watched a large aspherical Germanium front lens for a military
vehicle thermal imager being diamond-turned. The tool resembled a
brazed carbide bit. The finish it left looked mirror-smooth to me.
They use a wavelength about 10X longer than visible light and are less
sensitive to roughness.
jsw