Blue Loctite would probably be fine, red Loctite definitely. As long as you don't plan on taking it apart without significant effort.

Red Loctite (requires heat to remove) would likely hold it just fine On it’s own. Even blue loctite probably would.

Red loctite and jam nuts together on either side of the coupler would be very unlikely to come loose.

https://en.wikipedia.org/wiki/Jam_nut

Through drill with a cotter pin so you can take it apart if needed.

The control wheels themselves are just held on by hub nuts (backed against the mount pin). So long as the rods joined by the coupling nut won’t unthread, I’ll be happy. Much thanks! :)

Oh, hadn’t considered that. If I can make it a tight-enough fit for the pin, there wouldn’t even be any play in the rod. Thanks for the idea. :)

Set screws on the coupling nut.

Use orange loctite...strength of red...removal ease of blue

My preference is a jam nut. Just put another nut on and tighten it, ideally one on both sides of the connection. They use it for tie-rods on cars, it should hold the table saw.

Main advantage is it's easy to take apart, And doesn't require drilling or tapping what you have

That is what roll pins or taper pins are used for. You likely don't have a tiny taper reamer so use a roll pin.

I'd toss a nut on the threaded rod to lock the coupler in place and use a little loctite.

https://www.boltscience.com/pages/twonuts.htm

Lock washers.

As the other poster said, use a roll pin. I would use blue loctite anyway, tighten your thread, then drill for a small roll pin. Will last forever, but could be taken apart with a punch and a bit of grunt if you had to.

Another option is superglue. If you ever want to remove it, a little heat from a propane torch is all that's needed to make the superglue release its bond.

Does red loctite still come in a blue bottle?

Might not be enough thread for a full sized jam nut a half nut should do it. Stick a bit of loctite on there to be safe and it should be scookum as frig.

Blue locktite with a tightend nut is pretty tough, I think I would hold just fine. Has held on my heavy duty bike for like a year now, with similar twisting a ton from a trailer. It is wheels on a table, I thing you are good with countered nuts to be honest, they get super tight and don't separate.

Some of the blue loctite versions are cyanoacrylate glues. Superglue (the brand) also makes threadlocker.

no that's the other brand loctit had blue in the red bottle.

don't do shit

any epoxy will do. Be sure there is lots of thread engagement. If you have to undo it a torch heating it to 250F or higher will degrade the epoxy.

Put a couple of roll pins through the coupling to lock it. You can always punch them out if you ever need to take it apart

Only if they are nylon tipped set screws. Otherwise the threads on the original shaft and all-thread will get totally jacked up.

Scookum? do we have a fellow AvE fan in the house? :)

If you can find bolts long enough, I would suggest using graded bolts instead of threaded rod... Hardware store threaded rod is really soft material (saves cost in manufacturing) and will be bendable by hand in this application unless you have a bearing near the control wheels to keep the operator from applying any bending forces to the extension. 1/2" grade 8 bolts are pretty easy to find and will be much stronger.

I know I am

And in a pinch, nail polish. Never would have thought I needed that info, but some day you might. Came in handy for me once

they’re useful as a rough torque indicator. Do jack shit for preventing loosening.

They are mostly useful for assembly. you can put an impact on a bolt and nut in a thru hole and hit it without having to trap the nut with a wrench, because the lock washer will “bite”

I got a coupling nuts right here!

extend with a tube that fits over the shaft, with slots that fit over the pin

You could swags the coupler - use a large pair of bolt cutters and crimp the fitting onto the threaded rod

Your looking at the solution, do the same as how the handle was fixed to the shaft. Drill a hole in each end of the coupling nut and shaft, while in place on the shaft, and stick a roll pin through it. It's reversible and cheap and easy.

Any of the other suggestions (except for welding) will loosen up at some point.

I too love me a good jam nut but in an environment with high vibrations and possibly temperature changes there's no beating a jamnut with locktite. Still can be undone without having to permanently change anything on the device, just need one more step (heat) to get it apart when you need to.

I'd just put a hole on each end of the nut and lock it in place with set screws