What's a good adhesive or epoxy for adhering to metal that can be drilled and tapped?

I've got a 1/4" copper fitting. I'm looking for a non-conductive adhesive to fill it up halfway, drill and tap it so a spark plug can screw into the end. I was trying to find a nut earlier that would screw onto the end of a spark plug with an o-ring, no luck at the hardware store. I'll probably do the same thing with a few larger sized nuts: fill, drill, tap.  And I'm just looking for a decently priced multi-purpose adhesive (non-conductive). And I will be needing a conductive one fairly soon.  JBweld seems to be popular in some groups. I don't know if it's non-conductive.

It would also be nice if it could adhere to pvc, too. :-)

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JB weld should be very good, but it does contain iron. At low voltages it seems completely nonconductive, but I don't know how it would behave if HV were applied to it.

I don't know if the effective breakdown voltage would be significantly reduced due to the iron content, but you might want to keep it in mind if you use it to withstand any HV, as your response below suggest you might.
Vorenus (author)  LargeMouthBass6 years ago
I was a little apprehensive about the effect of high voltage. There isn't a list of popular compounds with their behaviors at high and low voltage. So I just have to experiment and see what happens.

What really surprised me was the warning on the back of the jbweld that said good for temp below 200F. That might be a problem.
lemonie6 years ago

You're making some kind of gun with copper then?
How about making a spark-gap instead of using a plug?

Vorenus (author)  lemonie6 years ago
Gun? No. I've got some 1/4" copper pipe and it's a cheap, easy container that's conductive. If I wanted to shoot a gun, I'd go out to the range with my friends. Water is sort of a new hobby for me. I'm using the spark plug as the spark gap first. Then I'll use the pipe as the cathode and create an anode to take the place of the spark plug. I was searching through the prior art earlier and found a bunch of neat patents that I want to build. Some were concerning electrolysis via HV, others the HV creation of steam. None of which use the chemicals to decrease the resistance of the solution for electrolysis. I'm not a big fan of added chemicals. But it's the electric steam generators that have got me stumped. Hence the decreased volume of water per unit of power. I'm still going to get hydrogen production. But I'm going to try different ways to cut down on the hydrogen production and increase steam.

I'm interested in learning about water in it's various states. I'm always up for new reference material, if you can recommend anything.
lemonie Vorenus6 years ago

Sorry, I'm ill and missed that you were the same author...
Water references I'm not too sure about for what you're interested in, but if I think of anything I'll post it.

One idea I do have, is to use a long vertical pipe, say 1 metre. Leave the top open so that you've only got the pressure of 1m water on the electrode at the bottom. If the thing develops a lot of gas (inc. steam) in a burst then the worst that happens is you get a fountain.
A development idea only, but easily done.

Vorenus (author)  lemonie6 years ago
Thank you. Steam with a low atomic hydrogen and oxygen content is the goal, for now. :-) Then I'll probably go for the threshold of superheated steam, whatever that is. I think the definition has changed over time. I'm doing everything in very small quantities, so if I get little pops with my lighter, it's a no go.
JB Weld is probably your best bet for non-conductive epoxy