[ATM] ATM Grit Sequence for 8" Mirror

[Royston_Jeremy at emc.com (Royston_Jeremy@emc.com)]

Hello Satish,
	The grits which I use are:

#80, #120, #220, #400, #600 silicon carbide, then M302 1/2, M303, M303 1/2
aluminium oxide
You'll need about 100g cerium oxide for polishing
The above grades of aluminium oxide are from the British American Optical
Company, since defunct, you'll have to use equivalents. It's well worth
using aluminium oxide, you save a lot of time polishing.
You'll need about 500g of #80, 50g of #220, 25g each of the remaining SiC,
10g of each aluminium oxide
You can use the flashlight and water method to determine the radius. If you
have a straightedge or steel rule and various drills you can use the
following method.
Lay the straightedge over the mirror diameter, then see if you can get the
tip of the drill shank (the round end, not the end which drills) just under
the straightedge. You can increase the radius by using tool on top, decrease
it with mirror on top. 
When grinding with #80 see that you grind right out to the edge, often one
gets a flat edge, which you can't grind out later.

Best wishes, Jerry 


-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf Of
Satish K. Pagare
Sent: 30 January 2004 09:44
To: atm@atmlist.net
Subject: [ATM] ATM Grit Sequence for 8" Mirror


Dear List,

I am almost done with a glass tile/plaster tool. I 
need to start the grinding now. Though I have read on 
many atm pages about the grits and all. Generally for 
an 8" what exactly sequence of grits should I use ? 
And do I also have to buy Cerium Oxide along with 
Silicon Carbide ?

Its too early to ask, but how to measure the
sagitta while rough grinding ? Using a metal ruler
and some already marked up cardboard strip or how?
I dont have access to dial indicator or such stuff.
Any easy way around ?

Thanks and Warm Regards,
Satish/

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