Re: ATM Advice with Flexing a 16"

["Peter" <peter@kitgear.com>]

Hi Bill,

Thanks for your message.

Sorry that I misunderstood and after reading other posts it looks like I am
probably the only who did.

In any case, I am quite eager to flex my 16" mirror and I look forward to
support from the ATM people on this list to help guide me through this.

Cheers,

Peter
----- Original Message -----
From: Bill Kelley <flex@commspeed.net>
To: Peter <peter@kitgear.com>; Ken Hunter <kb7h@onemain.com>;
<atm@shore.net>
Sent: Saturday, January 18, 2003 7:16 PM
Subject: Re: ATM Advice with Flexing a 16"


>
> Peter and others,
>
> SORRY about the misunderstanding. It should have read hog out the back
> convex..
> After reading Alan's article I assumed everyone understood that the
optimal
> back shape
> for a flex mirror is CONVEX.The program will calculate the radius by
> entering 0's
> for back shape and taper exponent. The exact radius of the convex back is
> not critical-
> generally a meniscus with a back convexity approximating the front will
flex
> to an elegant
> figure.
>
> I read wedge from the back with the mirror face down on a plate glass
> support and positioned
> against two posts at the edge.. A dial indicator overhangs the back of the
> mirror.
> The photo in the Nov. 2000 S&T article shows the set up for measuring
> sagitta and wedge.
> A micrometer reading around the edge will serve as well.
>
> And yes- my meager web site, www.flexmirror.com . needs some real content,
> photos
> and illustrations.
>
> Again- mea culpa- sorry if I misled you.
>
> Bill Kelley
>
> .
>
>
> ----- Original Message -----
> From: "Peter" <peter@kitgear.com>
> To: "Bill Kelley" <flex@commspeed.net>; "Ken Hunter" <kb7h@onemain.com>;
> <atm@shore.net>
> Sent: Friday, January 17, 2003 9:07 PM
> Subject: Re: ATM Advice with Flexing a 16"
>
>
> > Hi,
> >
> > Good advice!
> >
> > Should I grind the back flat before hogging it out because it has about
> > 0.012" of waviness near the edge.
> >
> > Thanks,
> >
> > ----- Original Message -----
> > From: Bill Kelley <flex@commspeed.net>
> > To: Ken Hunter <kb7h@onemain.com>; Peter <peter@kitgear.com>;
> > <atm@shore.net>
> > Sent: Friday, January 17, 2003 10:32 PM
> > Subject: Re: ATM Advice with Flexing a 16"
> >
> >
> > > Peter,
> > > My 2 cents. The back does not need to be fine ground. Hog out the
front,
> > hog
> > > out the back to the same curvature, dewedge, clean up, fine grind the
> > front
> > > (checking for wedge on the coarser grits), polish and figure a sphere.
A
> > #80
> > > grit surface on the back will not give you trouble working to 1/1000th
> > > wedge. An irregular bevel on the front might throw you off if you are
> > > reading wedge from the back with the mirror face down.
> > > Bill Kelley
> > >
>
>
>
>