[Milsurplus] Metal to crystal bond

[hwhall at compuserve.com]

>how the metal to quartz bond actually transfers the potential to make it oscillateThere needn't be a bond to the crystal, the FT-243 & others don't bond metal to the quartz. The crystal deforms mechanically in response to the electric field across the faces (& when it "relaxes" it makes an electric field). Metallizing faces provides a way to apply the field evenly across the face as well as a "grip" that a wire lead can attach to & support the crystal.
>would simple 'Super Glue' make a bond that would work?You mean like gluing a wire to the crystal plate or gluing a metal foil to it? The foil might work since it lets the electric field appear all across the plate. But the glue itself will probably act as a damper, lowering the resonant frequency or perhaps stopping it altogether. Getting the glue film microscopically thin might be a trick to accomplish, but might let it work.

WayneWB4OGM

-----Original Message-----
From: CL in NC via Milsurplus <milsurplus at mailman.qth.net>
To: Milsurplus <milsurplus at mailman.qth.net>
Sent: Thu, May 21, 2020 1:44 pm
Subject: [Milsurplus] Metal to crystal bond

I chased a few links on the process of putting metal on quartz, many of them are dated from the 80's onward with some really involved equipment.  But, how did they do it on FT241's back in the 40's?  A manual I bought from Tucker Electronics a couple years ago about a piece of equipment I have, included a type written in house procedure on crystal production, Q&A, and procedures to follow on the line at the Midland Company to tweak the frequencies of the crystals as they were checked after initial lapping to freq.  Does anyone know how the metal to quartz bond actually transfers the potential to make it oscillate, and would simple 'Super Glue' make a bond that would work?  I  sure there would be some compensation on grinding if Super Glue did work.  The 1934/35 QST's give a lot of info on grinding your own for FT243 style holders, including the formula for thickness to start from that is near the intended frequency and the design of a saw to cut quartz.

Charlie, W4MEC in NC
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