Need help keeping gearshift knob on.

Looking for new ideas, 'cause this ain't working permanently.

I have a black 7 billard ball (yes, a black 7- custom made by the factory for an "oddball"- me) that I am using as the gearshift knob in my '34.

Here's how I've done it: took a 5/16-24 locknut, sized it and drilled a hole in the ball that was slightly bigger than the OD's of the nut's peaks. Ran a 5/16-24 bolt into/thru the locknut about 1/4 inch. The hole was deep enough to allow me to insert the nut and have the bolt sticking out the end.
Mixed me up some JB Weld and put in the hole, then put the bolt/nut combo in the hole and let it harden. Removed the bolt and screwed the ball on my shifter...And it worked GREAT...for a while...

Then, after a few months, it seems like the JB Weld gets soft and the nut gets loose in the ball and it goes to flopping around..

Does anyone see what I might be doing wrong?
Is it normal for heat (hot weather in a closed car) to soften JB Weld?
What else could I use?
How else could I do this and have it work for good?

Thanks for any hints...

 

Not enought grip area I'm thinking. A bit of lathe work here. Take a piece of bar stock thread the ID . Turn the OD to your hole size and do a light knurl on the OD . Coat with a bit of JB or red Loc-***e and carefully press it into your 7 ball.

 

Years ago, I used an authentic 8 ball. I bought the appropriate heli-coil kit for the required threads (3/8, or 5/16) needed. The kit contained the correct size drill bit, tap, heli-coil, heli-coil insert tool, and a bit of thread locker..never had it loosen up, and have it to this day. I've had it on a few different cars.

 

Try using a Keen-sert in something like that.
They are what the crash test dummies use in the cast aluminum "skeleton" parts and they have to hold up to the crash or there goes a very expensive car with no useable data...
It would have to go in a fresh cleanly threadded hole to begin with to work.
A hogged out and glued up hole wouldn't hold it either.
http://alcoafastener.thomasnet.com/category/keenserts-reg-?&plpver=10&bc=3001584

 

x2 or just tap some threads into the ball itself.

 

i jb welded a .50 cal shell for a shift knob on my daily driver, its been on thier for over a year with no problems

 

Thanks guys - good suggestions all...and ones I had not thought of..that's why I asked...

 

Use a Coupling Nut and Loc***e.

A regular hex nut isn't long enough.