Nice information about making stems are in the Roth's book noticed recently here.. "Vacuum sealing techniques", for those interested in this book, let me know outside, I will post link..
I have already got a small test mold made from graphite, 13-pin.. My original intention was to arrange some kind of furnace in microwave oven and melt the glass directly in the mold with dumet wires inside.. But no luck yet, I am able to heat a piece of the carbide to 1000C, but the power is to small to heat all the mold with glass. Another thing is, that at this temperature, the graphite reacts with oxygen producing CO2 and degrades.. I think 10 cycles is maximum for one mold. The furnace with controlled atmosphere (nitrogen, argon, CO2 ..) would be the best.. I am going to ask my friend to test that process in their lab, he has a special tubular furnace able to go above 2000C ;-) I am preparing some short blogpost about my fail ;-) I will publish it tonight. Except that, I had also some small success, sealed argon tubes.. that post is already done: http://dalibor.farny.cz Dalibor 2012/6/17 Dalibor Farný <dali...@farny.cz> > Hi John, > > are You sure that only gravity is enough for the glass to flow to the > mold? At what temperatures? I tried 800C and no luck.. > > Dalibor > > > 2012/6/17 John Rehwinkel <jreh...@mac.com> > >> > How exactly would you proceed making - say - 13 pin tube bases? You >> need a lot of temperature for that and precisely formed tools. So far this >> is nothing I can see myself doing in the near future. I know a person who >> makes his own (borosilicate glass) sockets, I might be able to adopt the >> principle some day. >> >> The tool part isn't too tough, just carve it out of graphite with pin >> recesses. CNC machining would be the way I'd go, but back in the day it >> was done by reading scales on handwheels, and obviously it could still be >> done that way. Once you have your graphite mold/pin holder, >> get some nice 3-part pins and lead glass tubing of an appropriate >> diameter. Lead glass is the way to go here - it liquifies enough to >> gravity flow into molds like this. Slice off rings that have sufficient >> glass to make your bases, drop pins into your mold, put the glass ring >> around them, and melt the whole shebang. For extra niceness, you can >> have an upper mold half that forms little mounds of glass over >> the pins themselves and flattens the rest of the base into a disc. Let >> it cool, and violà! The first one will be a real bear, as you have to >> make the molds determine the amount of glass, temperature to use, etc. >> But once you have the molds made and the procedure down, >> you can knock out additional bases fairly easily. >> >> - John >> >> -- >> You received this message because you are subscribed to the Google Groups >> "neonixie-l" group. >> To post to this group, send an email to neonixie-l@googlegroups.com. >> To unsubscribe from this group, send email to >> neonixie-l+unsubscr...@googlegroups.com. >> For more options, visit this group at >> http://groups.google.com/group/neonixie-l?hl=en-GB. >> >> > > > -- > Dalibor Farny > http://dalibor.farny.cz > > > -- Dalibor Farny http://dalibor.farny.cz -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to neonixie-l@googlegroups.com. To unsubscribe from this group, send email to neonixie-l+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
