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- To: owner-atm@shore.net
- Subject: BOUNCE atm@shore.net: Non-member submission from [Kurt Hillig <khillig@Chem.LSA.umich.edu>]
- From: owner-atm@shore.net
- Date: Tue, 15 Oct 1996 10:55:27 -0400 (EDT)
>From atm-owner Tue Oct 15 10:55:23 1996 Received: from Chem.LSA.umich.edu (U.Chem.LSA.UMich.Edu [141.211.68.92]) by relay1.shore.net (8.7.5/8.7.3) with SMTP id KAA11781 for <atm@shore.net>; Tue, 15 Oct 1996 10:55:23 -0400 (EDT) Received: from Be.Chem.LSA.UMich.Edu by Chem.LSA.umich.edu (951211.SGI.8.6.12.PATCH1042/1123-1.0(Chem)) id KAA09517; Tue, 15 Oct 1996 10:55:15 -0400 Date: Tue, 15 Oct 1996 10:55:15 -0400 (EDT) From: Kurt Hillig <khillig@Chem.LSA.umich.edu> Reply-To: Kurt Hillig <khillig@umich.edu> To: BRYAN LEENHEER <BLEENHEE@millersqa.com> cc: K1JJ@aol.com, akelly@ghgcorp.com, atm@shore.net Subject: Re: ATM Radius of Curvature! ACK! In-Reply-To: <s262f5fb.075@millersqa.com> Message-ID: <Pine.ULT.3.95.961015104400.830D-100000@Be.Chem.LSA.UMich.Edu> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII On Tue, 15 Oct 1996, BRYAN LEENHEER wrote: > I just figured out that the sagitta of my four inch f/12 will be .020"! How > am I supposed to get this small amount of glass out of the middle of the > mirror? I made the radius checking tool that Texereau recommends, but > the curve is so shallow that I can't even tell that it's there! One way to get at least an approximate measure of the sag without going through the bother of making a spherometer is to pick up a *good* straightedge - a steel bar 3/4" or 1" square by whatever length you need, ground flat with a good surface grinder, is ideal - and a leaf (aka "feeler") gauge, a set of thin stainless strips of known thickness (usually used to measure the gap on spark plugs). Lay the bar across the mirror and slide the feaves under the gap at the center, increasing the thickness until it just fits; if the stack is too tall, the bar will rock, so it's pretty easy to tell when you've hit it. If you get a couple sets of gauges, you can also measure convex surfaces with this. It's easier on larger mirrors, but even on a 4" you should be able to measure the depth to 0.001", maybe half that of the gauges include some leaves with half-thousandth thicknesses (probably 0.0015" and 0.0025", as 0.0005" is a tad on the fragile side). Dr. Kurt Hillig Dept. of Chemistry I always tell the fax (313)647-4865 University of Michigan absolute truth phone (313)647-2867 Ann Arbor, MI 48109-1055 as I see it. X.500 khillig@umich.edu Computers were invented to help people waste more time faster.
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