[ATM] Hogging!!!

[KR]

Hello Georgia,

Even 5" seems a little big to dig out the centre. (I used a 2" pipe cap on a 
10"). Once you get the centre going, coc,  you can resort to chordal
strokes inside or up to the edge. However you seem to like constructing 
things. How about a spherometer? I found it a very reliable way to determine
 how spherical things were going. Even a 3" straight edge with a dial 
caliper mounted in the centre would do ( a la Richard). You grind until you 
have the same
measurement over the entire mirror. There's no guessing. Have fun!

another humble novice, sometimes
KR

----- Original Message ----- 
From: "Norm Prince" <norman.prince at verizon.net>
To: <atm at atmlist.net>
Sent: Saturday, January 20, 2007 4:47 PM
Subject: [ATM] Hogging!!!


>
> What i really wanted to ask about though was subdiameter tool hogging. 
> I've selected three canidates for the 12" blank.  They are as follows: an 
> almost 5" piece of plate steel (from god only knows what)...an almost 6" 
> ring (outer housing of a big roller bearing), and a 4.5ish grind stone 
> (granddads ole time axe grinder...just thought it might save me the 
> grit???).  I would be so delighted to hear the range of opinions expressed 
> about which is the best choice.  I posted a pic of the canidates along 
> with a pic of the edge grinding set up at 
> http://mysite.verizon.net/cmb15s7x/temp.htm
>
> ...but what i really need some input on is strokes for said sub-diam 
> hogging.  Are these CoC?...tool on top or mirror???...and length of stroke 
> is a bit of ??? too...almost to the edge?..how much is almost?  I've only 
> made 8" mirror to date, and i used a full diameter tool; grinding almost 
> exclusivly mirror on top...any input would be greatly appreciated.
>
> Your humble novice,
> -norm-
> Georgia, USA (land of bad seeing)
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