[Boatanchors] Ceramics help? Yes, it's boatanchor-related.

[Glenn Little WB4UIV]

This looks like the HV plastic insulators in a 25KW GE TV Transmitter 
that I disassembled. All of the parts made of this material had 
deteriorated to the point of falling apart when touched.
The quote sounds like Harris.

TFE might be your best choice.


73
Glenn
WB4UIV



  At 11:06 AM 5/6/2009, mikea wrote:
>Amateur radio leads into all manner of interesting side-topics,
>including in this case needing to do some fairly high-precision ceramics
>construction. I'm also a Really Cheap Bastard who's unwilling to pay as
>much as the manufacturer wants for three small ceramic widgets if I can
>make them myself.
>
>I refer the interested reader to
>those parts of <http://mikea.ath.cx/tubepix/> that refer to the Jettron
>socket, and in particular to the image of the insulating ceramic spacer
>to be found at <http://mikea.ath.cx/tubepix/8791-socket-washer.jpg>.
>(caution: 1,548,661 byte image)
>
>Those spacers are geting pretty crumbly,and fell apart on me as I was
>inspecting things. They are each 1/2" OD and 1/16" thick at their
>widest, with a 5/16" long 5/16" diameter shoulder, drilled to pass a #6
>screw. The manufacturer wants $167.50 for three of them. Yes, $56.00
>each, pretty near, for each of those little yellowish pieces of molded
>porcelain. The manufacturer's quote came as rather a surprise, though I
>should have expected it: the socket costs something like $500 new.
>
>The spacers are nothing special, just unglazed fired porcelain. I
>have access to a porcelain kiln, and I have a drill press and bits
>suitable for making molds. Now I need a low-shrinkage porcelain with
>good insulating properties and reasonable mechanical properties. The
>potential across that 1/16" shoulder will be about 1000 Volts, and it
>will be under no more than 50 pounds compressive force from the nut and
>washers. That's not a lot of force, and the flat washer spreads it out
>evenly.
>
>I'm thinking about machining the mold cavities from split plaster
>blocks, using flat-bottomed Forstner (or Pforstner) bits, though wood
>might well suffice. I see a fair (or perhaps even unfair) amount of
>experimentation coming up.
>
>I'm also thinking about getting a chunk of PTFE rod and finding a small
>lathe. That may turn out to be less work and less expense overall.
>
>Comments? Suggestions? Advice? Pointers?
>
>--
>Mike Andrews, W5EGO
>mikea at mikea.ath.cx
>Tired old sysadmin
>______________________________________________________________
>Boatanchors mailing list
>Home: http://mailman.qth.net/mailman/listinfo/boatanchors
>Help: http://mailman.qth.net/mmfaq.htm
>Post: mailto:Boatanchors at mailman.qth.net
>
>This list hosted by: http://www.qsl.net
>Please help support this email list: http://www.qsl.net/donate.html