Posts Made By: Edward DeMarco

Could someone tell me the lowest F/# recommended for an 8" mirror
and why you would not want to go below this #. I polish optics for a
living but it has always been to customer specs and I have never gotten
into lens design. So I don't understand what kind of problems can be
caused by making the mirror to fast.

Thanks..............

Great job Jack, I love to see the things people come up with
to make life easier.

Photox Optical Systems


http://www.photox.co.uk/EvaporationChemicalsAndAccessories/evaporationchemicals.htm

I have not had any experience with this company but it
looks like they have what you are looking for.

Hope this helps
Ed.................

Hi James,
If you are interested in a third opinion at no charge I can test
the mirror for you on a Zygo Mark 4 interferometer. Is it coated?
If so then the max diameter I can check is 4” if it is not coated then
I can check up to 6” diameter. Do you know the material type?

How about the 12 volt batteries they use to power kids toy jeeps.
They are only about 6" wide and about 4" high. You should get
pretty good mileage out of a charge. I don't think they weigh much.

Later
Ed DeMarco…………….

Hi Jason

I find a tolerance of +/- .002” on center thickness and diameter to be

fairly easy to hold. And the radius tolerance is better specified as a percent

of the radius .1% - .5% a higher % as the radius increases. because a
1" radius +/- .001" on say a 2" dia. part is not to hard to do but a 10" radius
+/- .001 on that same 2" dia. part would be very difficult. I have done some
very difficult lenses in my times ranging from a .040" roc +/- .0005" up to a
25" roc +/- .040". The 25" radius lens was a 2.6" square lens made of sapphire
and it had a center thickness of about .125" +/- .001" It also had to be polished
on the edges and the bevels. I have also done thickness tolerances as tight as
+/- 10 millionths but that was on flat work. One of the most important things is
that the shop you go to has the equipment that can accurately measure what
you are looking for.

Hope this has helped
Ed.................................

Hi Robert, that is an interesting grinding / polishing method.
It looks very useful for parts with odd shapes but the surface
roughness is not as good as it could be. I read two different
articles about the Jet Polishing one of them claimed a surface
roughness of 3.6nm and the other was 1nm . The material
was BK-7. You can easily get down to 1nm on BK-7 with
a pad or pitch polishing. When people refer to superpolishing
they are trying to get down in the area of 0.05nm - 0.20nm
depending on the material being polished.
Regards,
Ed DeMarco

Hi Jason,

We use to pay about $10 for 1" Dia. by .160" thick blank and I think about
$70 for a 3.250" Dia. by .200 thick blank. What is your interest in CaF2?

Ed D………..

I Think these are the router bits you are talking about.

http://pricecutter.com/product.asp_Q_pn_E_P16-2865_A_cn_E_361