Re: [ATM] industrial polishing pads?

["David Harbour" <stainless_steel@suddenlink.net>]

Mike, all-

This is good tried and true wisdom. I finished a sixteen inch with the 
silkiest fine grind ever, by taking steps almost identical to what you  have 
iterated, here. It was a heavy blank, fine ground on the back, and very 
thick; it was cast in the thirties by Corning, as a series of experimental 
discs leading up to the five meter at Palomar. Now, this blank is already 
cored, with the plug still blocked in it, and I know the guy who owns it, 
and he would take  pocket change for it. It was probably meant for a 
Dall-Kirkham, because the central perforation is small. Here is a link where 
you can see the tool, still serviceable, and the mirror has been here for 45 
years; I lusted after it when I was a teenager; now, I would hurt myself to 
pick it up. It is still under the bed of Donnie's older brother- this is 
where it was when I was 14. I pass his house every evening, if anyone is 
interested. Here is the link to the article that has a fine picture of the 
tool and the mirror. The tool is 13.1" in diameter, and I always worked of 
course mirror up, with tool on top. No scratches, no gouges. Someone should 
rescue it before Donnie passes on. The tool will take pitch easily, and is 
still the same dimensions, as it is made of dimensionally stable material. 
It is approximately f/4.7.

Link:

http://www.atmsite.org/contrib/Harbour/Tool.html


Somebody rescue the tool and mirror before it is gone (before Donnie passes 
away, and no one knows what it is and it ends up in a garden somewhere). I 
can talk to Donnie about it again if anyone is interested; I go by his house 
every evening to go up and visit my wife's crypt in our beautiful mausoleum.

R-101


----- Original Message ----- 
From: "Mike Lockwood" <melockwo@uiuc.edu>
To: <atm@atmlist.net>
Sent: Tuesday, March 25, 2008 5:07 PM
Subject: Re: [ATM] industrial polishing pads?


> Hi,
>
> David Harbour wrote:
>> Okay, if they are about one micron in diameter, why not try 2
>> micron aluminum oxide directly on the pitch? I have read where one
>> can pre-polish on pitch with small abrasive, very fast. I have
>> never tried it; I was tempted, but somehow never got around it. Why
>> don't we find a less problematical way to cut down on fine
>> polishing time than pads? Anyone game to try this proposal?
>
> Cerium oxide for general polishing is often 1u-2u in size, but
> grinding to 1u with aluminum oxide is very beneficial and will cut
> down on polish time.
>
> If you are grinding glass on glass, you can go from 5u to 3u to 1u
> with no problems if you filter your water.  Be gentle - with the
> smaller grits (5u and under), for the first few minutes it will feel
> like nothing is happening and the mirror/tool is just gliding on the
> surface tension of the water layer.  Do NOT apply pressure to try to
> fix this - just keep working.  After a little swarf builds up, the
> surface tension is broken (soap might help too) and the disks manage
> to get a bit closer and grinding really begins.
>
> An extra 1/2 hr of 3u and 1/2 hr of 1u will save you hours of
> polishing, and the physical effort is almost nothing.  After a nice 1u
> grind the mirror becomes transparent.  There's just something about a
> 1u-grind that is quite beautiful.
>
> Mike Lockwood
>
> PS - I am also getting two error messages from someone's server every
> time I post to the ATM list.  It's annoying.
>
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 


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