Has anyone tried using themal paste as lubricant between the threads of metal bodied flashlights? This seems like an obvious way to improve heat sinking in flashlights (LED in particular) as it would allow better heat transfer between parts. Would this be damaging to the rubber o-rings? You could always silicone grease the o-ring and use thermal paste on the threads.
Haven't tried it, but I don't think it would damage anything. Most thermal pastes I've dealt with are silicone greases, with various particles added for thermal conductivity.
However, I'm not sure it would make much difference in heat transfer. Thermal paste by itself isn't a great conductor of heat; it's just a lot better than an air gap. When installing a CPU heatsink, the idea is to get a very thin, even layer of compound between the chip and sink - the compound fills in the gaps at a microscopic level. Most assemblies have a spring clip or some other method of applying force to the junction, to keep them together and squeeze out any excess.
This is also why modders and overclockers will lap their heatsinks (and sometimes, the chips themselves) with very fine abrasives, to get them as flat and smooth as possible. This allows them to use less thermal compound, and get better heat transfer rates.
I'd think that for the distances in a threaded assembly, you wouldn't see much improvement with a thermal compound over a standard thread lube. Threads have to have some play in them, or else they tend to bind or gall when tightened, even with lube.
Of course, this is all conjecture, and I don't think using thermal compound would hurt anything, so somebody give it a shot and see.
HDS uses this when putting the light engine in the light. It is put on the threads just like a lubricant, but transfers heat better than a normal lubricant.
Problably wont make much of a difference, but Henry does the small things just right (except the clip on the HDS EDC..... sigh)
I use a small amount of Permatex anti-seize on electrically conductive threads (like in the Fenix L1T/L2T head). It's a good lubricant, it is electrically conductive, and seems to work fairly well as a thermal conductor also. Anti-seize contains aluminum particles to give it these qualities. It is not as effective as a thermal compound, but it has much better lubricating properties.
I've used Dow Corning silicone heatsink compound on the threads of a few 1 and 3W lights to assist heat transfer to the body or head. But these aren't focusable, so once screwed together, that was it.
One light did feel noticably warmer afterwards. So, it did help.
As for Permatex anti-seize, it's a good substitute, but their high termperature version may be better as it uses copper instead of aluminum.
But be careful applying it, it gets everywhere in no time!
I just received my HDS 42XRGT in the mail the other day and was horrified at the nail to chalkboard sound that was produced when screwing and unscrewing it. I couldn't find any silicon lube locally and thought about Vaseline, but then I remembered I had a giant tube of Artic Silver Ceramique laying around somewhere. I applied a thin bead around the outside threads and screwed it down. Smooth as silk now and completely quiet. It doesn't leak even though I applied quite liberally. I'll keep you guys informed on how it does. It seems OK - if you can get over the white goop when you change batteries.