Re: [ATM] Abrasives

["Thomas Janstrom" <thomas@moiler.com>]

The grits I use regardless of mirror size are:
80 SiC (hogging only)
220 SiC
600 SiC
1200 SiC
25 mic AlO
9 mic AlO
5 mic AlO (only if I really want to get a quicker polish)

I know that going from 1200 to 25mic might be seen as a bit of backwards
step, I feel that as SiC and AlO grind in slightly different ways going back
sets the stage as it were for the real fine AlO grits.

Thomas.

PS. Feel free to comment as you wish, this is just how I do it, YMMV.

-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf Of
Thomas A. Moulton
Sent: Monday, 5 March 2007 9:20 AM
To: Mel Bartels; atm@atmlist.net
Subject: Re: [ATM] Abrasives

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
>
>
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 

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