Re: [ATM] Abrasives

["Thomas A. Moulton" <tom@moulton.us>]

Mel,

What size mirrors does this apply to?

In my grit kits I only supply 320 on the larger ones.
(If I add 5 Micron I add #320)

My thought process was that with smaller mirrors you will spend more time
cleaning up between grits than grinding that contamination risk is higher
from sloppy cleaning.

I supply the extra grits for 12" and above.

If there is good reason to add #500 I will.

Tom
GotGrit.com
----- Original Message ----- 
From: "Mel Bartels" <mbartels@bbastrodesigns.com>
To: <atm@atmlist.net>
Sent: Sunday, March 04, 2007 1:16 PM
Subject: Re: [ATM] Abrasives


>> As my basement is too cold to polish anything, I have resumed another old
>> project, My 12.5" f/6 telescope with a pre-generated curve. I just
>> completed grinding with 320 Silicon Oxide. I have 500 SiO as well as 25
>> micron AlO, any suggestions as to which I should use next?
>
>
> Since both have about the same particle size, it can be confusing which to
> select.
>
> I always use the 500 SiO has the final carborundum before heading into
> smoothing grinding with AlO.  320 is way too coarse as a final grit before
> smoothing.  The odds of leaving subsurface fractures that cause trouble
> during polishing are too high.
>
> The 25 micron AlO will leave pits about 1/3 the size of the 500 carbo.  So
> it's well worth your time to do both the 500 carbo and 25 micron aluminum
> oxide.
>
> Mel Bartels
>
>
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> 

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