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

[Steve Beccue <lsteve@beccue.com>]

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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