Re: [ATM] A polishing we will go!

["ed witkowski" <edwski@comcast.net>]

Hi Tom,
The scratch sound was "grittier", while the polish squeak is more of a high
pitched "door in need of wd40" sound.
Just gets added to the experience column.
Enjoy your projects.

ed


-----Original Message-----
From: tom bouthillier [mailto:athenabout@hotmail.com] 
Sent: Tuesday, October 03, 2006 7:53 PM
To: edwski@comcast.net; atm@atmlist.net
Subject: RE: [ATM] A polishing we will go!

Ed, sorry to hear about the scratches. Hope there not to bad & have no real 
effect. I just wondered- you say you heard a sound when generating those 
scrathes. I hate to have you relive that moment but I wonder if you could 
describe it. Is it similar to the squeking when the wet is almost dry ? 
Knowing this sound might help me out in the future.


>From: edwski@comcast.net
>To: atm@atmlist.net Subject: [ATM] A polishing we will go!
>Date: Mon, 02 Oct 2006 21:42:11 +0000
>
>Greeting ATMers,
>Having made an 8 incher and 10 incher, I wanted to go for the gusto.
>Originally I was going to get a pregenerated 16 from Newport. Those plans 
>got delayed(luckily). A few weeks ago I purchased a ready to polish 18 inch

>from James Mulherin at OMI. The mirror arrived very well packed and fine 
>ground,  excellent! Looked too nice to polish. Our local mirror making 
>group meets at the NCA(National Capital Astronomers) mirror class run by 
>Guy Brandenburg(a big thank goes to Guy!).
>We had a old 12 inch pitch lap. After softening it with hot water, we 
>pressed it with 100 lbs of weight. Then the journey began. I began 
>polishing with cerox 1670. On the first night, I only manged to put in 45 
>minutes of polishing. The center was beginning to polish out. :)
>A week later, I cold pressed the lap for 30 minutes and began polishing.
>Holy Pitch Lap! It is quite a work out, especially when you start to 
>squeak. 45 minutes and I needed a break. 15 minutes of cold pressing and 
>back to polishing.  All was great until I heard the most dreaded sound you 
>can hear while grinding/polishing. @$%&* I had scratched the blank!!. There

>are a few, one or two that I don't think will get polished out. The pitch 
>lap was made on a base of some-sort of poured material, this is ok, but 
>there were still tiles from grinding under the pitch. GRRRRR. I was back 
>again this past friday, we switched to another pitch lap, this one is 
>better. Total actual polishing so far, 3.75 hours. The polish is all the 
>way to the edge, no hazy areas, just a nice smooth polish. Hard work but 
>fun. I plan on a total of at least 8 hours of polishing before taking a 
>look on the test stand.
>
>Until Then, Grind more and Enjoy the Sky
>
>Ed Witkowski
>Woodbridge, VA
>
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