This threads been helping me pass the time. Please forgive, but i wanna keep it going! "I fukin grabbed it!" For some reason, had me laughing. I laugh every time i read that.. ?
Its been awhile since i used these formulas, but out of curiousity i did a quick-n-dirty on the thread pullout force of a 5/16-24 x 1/2 thread in 6061-t6. It came in at 5300lbs. Its unlikely that you exceeded this value with your hands.
In bending, the moment generated wouldnt likely strip the threads but would have broken the threaded steel shank from the handle. The moment needed to break the handle wouldnt likely be possible with a human hand.
It's very likely that your threaded aluminum either wasnt properly machined, or had some pre-existing damage.
As a former machinist who went back to school for an engineering degree, then started gunsmithing as a fun hobby, i personally wouldn't use epoxy on a bolt handle knob.
Thats just a personal choice though, theres nothing mechanically wrong with it. As long as the customer knows its there, its easy to defeat the epoxy and remove the knob.
Personally, i always make my bolt knobs from left-over barrel blank stumps. Usually its either 416 re-sulpherized or 4140 re-sulpherized. This is irrelevant though, as even 6061-t6 shouldnt be experiencing thread pullout or excessive thread wear.
I like to rough out a set of 6061 soft-jaws to fit the knob, and using a couple drops of permatex blue, and the specifications set forth as per IFI 5th Edition Technical Data N-12/N-16, using Equation (1) and a coefficient K=0.15 for plated fasteners, torque the knob to 14 lb-ft.
I know the bolt handle shank isn't plated, but the blue permatex changes the friction coefficient of the fastener and makes the reduction from 19lb-ft to 14lb-ft prudent.
I've never heard of one of my bolt knobs unintentionally coming off, nor had any reports of damaged threads, and the knob can easily be removed non-destructively with soft-jaw equipped pliers or destructively with non soft-jaw equipped pliers.
I typically recommend these types of pliars for removal of my bolt knobs:
https://www.homedepot.com/p/HDX-10-in-Soft-Jaw-Pliers-66011/204277473
BTW: I noticed that i got "trophy points", and it appears that they have something to do with "likes".
What are these?