[ARC5] WHINK and crystals.

wb3fau55 at neo.rr.com wb3fau55 at neo.rr.com
Sun Jun 30 09:29:42 EDT 2013 

I agree with you Bruce.  I did my  xtals  with wet and  dry  sandpaper on a flat benchtop worked FB. Russ.
---- Bruce Long <coolbrucelong at yahoo.com> wrote: 
> I doubt very much optical flatness is required for grinding a crystal.  It is difficult to decide what degree of flatness is adequate from comparison with modern crystal manufacturing practice as most modern crystals have a lens shaped cross section to reduce spurious responses.  Having said that the contour grinding buckets are nothing more than sell or maybe even cast iron.
> 
> The planetary blank grinding machines use ordinary steel surfaces ground flat with ordinary machine shop grinders.
> 
> For this reason  I suspect  ordinary flat float (plate) grass is good enough for occasional use.  The next step up would be to buy a small flat of precision ground steel plate from mcmaster carr or the like.
> 
> I suspect the grinding technique- ie uneven pressure,  not using figure 8  or equivalent grinding motion is the larger problem
> 
> 
> 
> ________________________________
>  From: J. Forster <jfor at quikus.com>
> To: Dennis Monticelli <dennis.monticelli at gmail.com> 
> Cc: ARC-5 Maillist <arc5 at mailman.qth.net> 
> Sent: Friday, June 28, 2013 12:32 PM
> Subject: Re: [ARC5] WHINK and crystals.
>  
> 
> Optical flats come in all sizes. I have a 16" one, about 3" thick, that I
> got surplus years ago.
> 
> I really think a piece of plate glass, like a very small table top, will
> work just fine.
> 
> I'd go to a local glass shop and ask for a piece of scrap, then pay a few
> bucks to get the edges sanded unsharp.
> 
> YMMV,
> 
> -John
> 
> ==================
> 
> 
> > True, though they are much smaller than your typical 8" reticule.
> >
> >
> > On Fri, Jun 28, 2013 at 9:19 AM, J. Forster <jfor at quikus.com> wrote:
> >
> >> Optical flats, used w/ LASERs are probably a whole lot flatter. They are
> >> often good to 1/100th of a wavelength of roughly 500 nM light, or 5 nM.
> >>
> >> They are pretty expensive though. Think $300 for a 1" OD, 1" thick one.
> >>
> >> You can sometimes be picked up cheap on eBay.
> >>
> >> -John
> >>
> >> =================
> >>
> >>
> >>
> >>
> >> > Good input, Hutch.
> >> >
> >> > There is NOTHING flatter than a glass reticule.  We're talking
> >> microns.
> >> >  These are very hard to find, even here in Si valley among all the
> >> surplus
> >> > shops.  The reason is not just recycling, it has more to do with the
> >> fact
> >> > that these masks represent the IC design itself and all such
> >> information
> >> > is
> >> > deemed highly proprietary.  Hence this stuff just does not end up in
> >> the
> >> > surplus channels.
> >> >
> >> > Dennis AE6C
> >> >
> >> >
> >> >
> >> >
> >> > On Fri, Jun 28, 2013 at 8:21 AM, John Hutchins
> >> > <jphutch60bj at gmail.com>wrote:
> >> >
> >> >> Group -
> >> >>
> >> >> This is good information,  is the procedures and materials and
> >> process
> >> >> document existing on a web page?
> >> >> Can the whole process be summarized?  If so since radio sites go up
> >> and
> >> >> down, same as with "yahoo group participation" could this be a
> >> Wikipedia
> >> >> page?
> >> >> On the subject of Glass:
> >> >> Glass plate you say,  find if you can;  glass used in making IC chips
> >> >> called a reticule;  This is very hard and thick glass, flatter than
> >> the
> >> >> world before Columbus!
> >> >> They used be very common and were discarded all the time;  Now
> >> reticule
> >> >> glass is recycled, but you may still have some sources out there.
> >> >> Hutch
> >> >>
> >> >>
> >> >> On 6/28/2013 8:55 AM, J. Forster wrote:
> >> >>
> >> >>> The guy used a mirror, probably because it was a cheap 'optical
> >> flat'.
> >> >>> Ande distortions are readily noticeable. Today, with 'float glass'
> >> >>> probably any glass plate from a hardware store will work...  thye
> >> >>> thicker
> >> >>> the better.
> >> >>>
> >> >>> As to grinding medium, fine gvrinding powder for amateur telescope
> >> >>> makers
> >> >>> is worth a try. It comes is a wide variety of grits, from gravel to
> >> >>> rouge.
> >> >>>
> >> >>> -John
> >> >>>
> >> >>> ================
> >> >>>
> >> >>>
> >> >>>
> >> >>>
> >> >>>  Gentlemen,
> >> >>>>
> >> >>>> For whatever it may be worth, I had occasion to observe a fellow
> >> radio
> >> >>>> amateur and CAP communications person who regularly ground
> >> crystals.
> >> >>>> I
> >> >>>> recall that he would accumulate a large number of FT-243 crystals
> >> of
> >> >>>> varying frequency and put them on the CAP frequency of 4585 kHz.
> >> He
> >> >>>> did
> >> >>>> a combination of lapping and etching.  I recall that he used a
> >> >>>> heavy-duty mirror surface for lapping.  The one thing I also recall
> >> >>>> was
> >> >>>> that, for periodic testing, he used two electrodes (sic) from an
> >> >>>> FT-243
> >> >>>> holder with leads attached and held the thing together with a stout
> >> >>>> wooden close-pin. This was wired into an oscillator which, in turn
> >> was
> >> >>>> hetrodyned with a BC-221 into a receiver (Remember, this was in
> >> >>>> probably
> >> >>>> 1959).  Apparently, the pressure was what was need to emulate the
> >> >>>> pressure the holder would provide.  He made crystals for CAP for
> >> >>>> probably 20-plus years with very good success.  I recall the
> >> >>>> "figure-8"
> >> >>>> pattern he'd use to lap/grind the crystals.  I do not know the
> >> >>>> chemicals
> >> >>>> nor compounds he used, but suspect it what you all mention, here.
> >> I
> >> >>>> may
> >> >>>> give it a try as I have some crystals near 3885 that are within
> >> >>>> reasonable distance down the band.  We'll see!
> >> >>>>
> >> >>>> Jeep K3HVG
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