I put together a copper thermowell by soldering some 3/16" tubing to 1/4" tubing and capping the end with silver solder. I then used a piece of 5/16" Teflon FEP tubing to slide over part of the 1/4" copper tube. This is VERY tight leakproof fit and the temperature port on my copper column is a little 1/4" copper stub. So my thermowell slides right into the hole on the column and seals when you press the teflon tube up onto it. Easy.
I have an Omega K-type Thermocouple that slides into the thermowell all the way to the end. I plan to use some heat shrink or a dab of hot glue to keep it securely in place. What i don't know is should I put some sort of thermal grease in there first like Arctic Alumina (heatsink grease), or some other kind of grease that is safe for copper/solder/thermocouple? Or no grease at all? I'm hoping to minimize lag times if possible becaust I'm running an LM reflux column, so temperature responsiveness is very critical.
I actually got my inspiration from this thread a couple years ago:
http://w.homedistiller.org/forum/viewto ... =2&t=47618" onclick="window.open(this.href);return false;" rel="nofollow