Re: [ATM] next mirror .. hand grind or build a grinding machine??

["tony gondola" <acgna@comcast.net>]

I think that's right. Switching to the machine is almost like begin a 
beginner again. No problem doing the monkey operations of grinding and 
polishing but getting to a good sphere and then machine figuring will really 
test you.

Tony

----- Original Message ----- 
From: "Steve Beccue" <lsteve@beccue.com>
To: "Robert OToole" <polaris@gsinet.net>
Cc: <atm@atmlist.net>
Sent: Saturday, August 05, 2006 8:44 AM
Subject: Re: [ATM] next mirror .. hand grind or build a grinding machine??


> Rob,
>
> I have done two 16" by hand.  I agree it becomes difficult only at the
> polishing stage.  Subsequently, I bought a mirror making machine.  Just
> the time to learn how to reliably get a good sphere with a machine was
> more than doing one 16" by hand.  Perhaps a sub-diameter lap, or two
> people pushing the lap, is more cost and time effective.
>
> Just my experience.  Others may have better justified opinions.
>
> Steve Beccue
> steve@beccue.com
>
> On Sat, 5 Aug 2006, Robert OToole wrote:
>
>> I'm working on a 6" f/8 mirror for my son right now, all by hand.  I've
>> done a few mirrors, all modest in size.    After this I have my sights on
>> some aperture and I want to grind a mirror in the 14" - 18" range.   I
>> don't expect to do more mirrors after that.
>>
>>   Anyway, I've heard that a grinding machine is the way to go on bigger
>> mirrors.  However, somehow I question putting the time, money, and
>> energy into building a grinding machine   for just one mirror! It would
>> become yet another project to complete.
>>
>>   Instead, I'm thinking of forging ahead and just spending the effort on
>> the mirror itself.  I've ground a 16" mirror before, all the way to the
>> polishing stage. However, it's the polishing stage which will be a
>> "bear" methinks.
>>
>>   Another half-way idea I had was the following:
>>   build a simplified machine ...  just a motor-driven turntable with a
>> pivoting overhead armature.   This would be for TOT work.  The turntable
>> would be for  just slowly spinning the mirror while I would manually
>> move the tool back-and-forth using the armature.  I would also be able
>> to stack weights on the arm to apply necessary pressure.
>>
>>   This idea isn't too bad since it takes most of the grunt work off my
>> shoulders.  It would be a lot simpler to build than a full grinding
>> machine.
>>
>>
>>
>>   Anyway, I want to solicit opinions and thoughts on this before moving
>> forward.
>>
>>   Thanks,
>> Rob
>>
>> -Robert OToole
>>
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