[JMS] How does one "grind a crystal" to change its frequency ?

Thu May 31 20:09:06 EDT 2007

What you need is a small (1" x 1" piece of 1/4" or 3/16" PLATE glass. You 
can get a piece from your local glass shop for nothing... I was lucky, my 
father was in the glass business,  HI. With this thickness glass, you have 
some thing "to hold on to"... (the edges). Plate glass is used for it's 
inability to "bend". The idea is to 'try; to get an 'even' grind. If you use 
just your finger, you will put more pressure on the center than the edges 
and ruin the parallelism. Yes, you can ruin one easily without even trying 
hard... We used to wash the blanks, holding them by the edges... and rubber 
gloves are a good idea. The surface tension be=tween the small piece of 
glass and the blank is 'supposed' to hold it... Never had any luck changing 
them more than a few kilocycles, OOPS I mean a few kiloHertz. You can rinse 
then off in tap water and then clean them with isopropyl alcohol.
Tap water in some areas contain impurities and the slightest bit will keep 
the thing from oscillating...that is why distilled water is recommended. 
More info???   73  Joe W4CBJ/WX4TRA.(Ancient One).

>From: john <johnmb at nc.rr.com>
>Reply-To: The James Millen Society Members Email Reflector 
><james_millen_society at mailman.qth.net>
>To: The James Millen Society Members Email Reflector 
><james_millen_society at mailman.qth.net>,james_millen_society at mailman.qth.net
>CC: Sherrill.Watkins at dgs.virginia.gov
>Subject: RE: [JMS] How does one "grind a crystal" to change its  frequency 
>?
>Date: Thu, 31 May 2007 19:29:17 -0400
>
>Just a question (and perhaps indicates why I have not been real successful 
>at moving a crystal very far before activity falls off)... how do you 
>"figure 8" the thing, without touching it ? They're such small slivers of 
>quartz, it's really hard to handle it. I suppose rubber gloves could be 
>used, and only use tweezers to lift it.  Cleaning it I guess could be done 
>in an ultrasonic cleaner.
>
>The "ancient ones" had a good process, that is not obvious....or....they 
>too ruined a lot of blanks!
>
>John K5MO
>
>
>
>
>At 06:32 PM 5/31/2007, Joe Rubin wrote:
>>Dear Sherrill, I used to "grind" crystals in the old days. An FT-243 can 
>>be taken apart by removing the face screws. Then the crystal blank is 
>>removed from the holder by slipping it out. The crystal is placed on a 
>>convenient plate glass square (about 4"x4") size irrelevant and a small 
>>amount fine of carborundum powder (you can use automobile valve grindind 
>>compound, the fine stuff only and 1/4" to 3/16"r the blank and usually 
>>rotated in a figure eight or so.  The idea iis to use very light pressure 
>>and keep the faces paralllel . A few 8 and the blank is washed very 
>>carefully , reassembled and tested on an oscillator or the intended xtal 
>>circuit. It is not a fool-proof method and often the thing will quit 
>>working a you cannot get it to oscillate again. The reasons vary but 
>>usually due to lack of parallism sm, or lack of cleanliness. The blank 
>>should be handed by the edges only. The crystal an only be moved so far (a 
>>few Kc) and if one is out of the amateur band I doubt it could be moved 
>>very far.
>>Crystals oscillate in the fundamental mode, that is if you have one for 
>>forty meters (7 mHz) it will oscillate there. An overtone crystals 
>>manufactured to perate in the second to fifth harmonic (7 x 2 = 14) (7 x 3 
>>= 21) ... of course there are special cases. The older Amateur Radio 
>>Handbooks used to have articles on this subject. I will try find some for 
>>you. The main thigs to remember are: paralellism, Cleanliness and a limit 
>>to the frequency excursion..  Let me know if you need more information or 
>>futher explanation.... 73  Joe  W4CBJ/WX4TRA.
>>
>>>From: "Sherrill Watkins" <Sherrill.Watkins at dgs.virginia.gov>
>>>Reply-To: The James Millen Society Members Email Reflector 
>>><james_millen_society at mailman.qth.net>
>>>To: "The James Millen Society Members Email Reflector" 
>>><james_millen_society at mailman.qth.net>
>>>Subject: [JMS] How does one "grind a crystal" to change  its frequency ?
>>>Date: Thu, 31 May 2007 10:27:47 -0400
>>>
>>>Friends and Members of the James Millen Society: Please be advised that 
>>>from
>>>time to time, I see FT-243 crystals for sale in odd frequencies; i.e. 
>>>that
>>>are outside of the amateur bands and of no use. Years ago, I heard that 
>>>it
>>>was possible to "grind" a crystal to raise its frequency. Also, I heard 
>>>that
>>>one could "rub" a crystal with pensel graphite to lower its frequency.
>>>Yet,
>>>I have never seen any article published in any major amateur publication
>>>including various handbooks, or magazines such as QST, Electric Radio, 
>>>The
>>>Old Timers Bulletin, etc. as to how this process is be performed.  Can 
>>>anyone
>>>refer me to a good source or explain the process in great detail? Also, 
>>>what
>>>is meant by the term, "overtone" crystal? Thank you very much. - Sherrill 
>>>W.
>>>k4own, member
>>>______________________________________________________________
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>>
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