In my experience, JBWELD is Garbage.
It was never stucturally strong enough for anything worthwhile... and would crumble with little stress.
Use Quik-Steel instead.
I believe quick-steel (plastics version / white)... is over 5000 psi, when fully cured.
It will be hard as a Rock, in about 5 to 6 min flat. So hard... that you will find it almost impossible to scratch with a metal nail.
Ive used it to make a custom adapter for a dishwasher hookup. I messed up the first attempt, as I didnt let it fully cure.. but,
the 2nd time... it held up Perfectly. Mind you... the pressure of the water, was very high.. and it never so much as leaked a single
drip.
Ive repaired cracked Laptops with it. Ive used it to make keychain adapters.
Unlike JBWELD, you can carve, drill, and shape it.. without it cracking and crumbling.
The stuff is absolutely the Best.
Just make sure you work Fast. Maybe 2 min to kneed the mix... and 2 min max to place / shape... as not long after that.. it will almost
immediately become an non-pliable Rock.
If not using the whole thing... fold the wrap over the end, then insert it end down into the tube... and seal the tube with the stopper.
Store in a dark / cool place, and it should remain usable for some time after. (You usually have to cut off a little bit of the end, as it
often gets a little crusty/cured)