Dave wrote:
If you want thermal insulation, then PTFE ...
John wrote:
I[t] needs to insulate electrical and thermal and metal would not do well.
Two machined pieces of glass-filled PTFE with holes to pass screws or plastic rivets through should work pretty well. You want some thermal insulation, but not too much (there has to be a heat flow path to ambient to allow the heater to work at a reasonable fraction of its capacity), so the thickness of the top part would need to be right and some experimentation might be required. I've made a number of machined parts out of plain PTFE and glass-filled PTFE -- either one is definitely do-able.
Straight PTFE is subject to cold-flowing, so if you used that some thought would need to be given to the through-bolts so everything would stay tight. Belleville washers are one common solution. But glass-filled PTFE is harder and more stable, and is the better choice for this job.
I've never machined polysulfone, but it is routinely done, so that is another choice. It is also available with glass filling.
Once a design was set and programmed, a small CNC mill could zip out enough parts to fill the next 100 years' volt-nut needs in ten minutes.
For those who haven't seen one, here is a top view of a 3458A reference board showing the LTZ1000 with its hat on: <http://cache.amobbs.com/bbs_upload782111/files_17/ourdev_466753.jpg>. As Frank noted, the bottom piece (not shown) is very important because it insulates the thermocouple joints where the part is soldered to the board.
Best regards, Charles _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
