DIY ARTICULATING HELPER ARM!!!

Agree with schuylergrace and Frank S, all kinds of positives.
T-handles a possibility, potentially get caught up in sleeves and cuffs. Having them part of kit, saved for useful manipulation might solve that.
Like Marv observes, the balls may lap in after awhile and slip; the centered bolt is large enough to delay it for some time.

Only detail I'd really alter is contour of the bracket clamping the spheres. Arch or peak in the middle, truss-like; averting bend or collapse with tightened fastener, backed up with heavy washers.

I have regularly used my articulating arm and noticed no degradation of clamping force over time. The mating surfaces between the ball bearings and the side brackets do wear with use but due to pressure rather than by rubbing together.
In use the clamp is kept loose until the correct position is found when it's then tightened very firmly. Adjustment whilst tightened isn't necessary so wear isn't an issue.
Wear with use would increase the surface area of the mating parts and allow greater friction between them anyway.
I used 10mm thick steel for the brackets and therefore didn't need to bend up the sides for added rigidity.
Use the largest ball bearings you can find, (mine are 25mm) and rusty (but wire brushed clean) is best.
A good source of free used large bearings is your local Caterpillar or heavy machinery dealer. Mine came from the main bearings allowing rotation between the body and tracks of a large excavator. The bearing was 400mm in diameter before I destroyed it to remove the balls themselves.
Also the plastic knob to tighten the assembly needs to be heavy duty, large in diameter and with a sturdy steel or brass insert for the thread. I used a 75mm diameter knob with an M12 thread. You need to screw it down tightly so movement is almost impossible.
The end result is extremely robust indeed.

I agree with schuylergrace..show the purpose for the completed tool at the front of the video, then show the building portion. And yes, glove friendly knobs would be a great feature to have on such a handy tool. Thanks for the excellent tool & video!

I like the idea of making the rods a press fit. I wondered about trying to anneal some balls then drilling and tapping them, but a simple press fit should work better. Thanks.

Another suggestion is to drill right through the annealed ball bearing whilst it's in the lathe, countersink one end, then weld or braze the shaft in place filling the countersink with weld metal, which is then ground or linished off to retain the spherical shape.
The holes in the brackets need to be perfectly aligned as matching pairs (drill them together) and be placed close to the ends of the brackets to allow maximum articulation of the shafts.
You will be very pleasantly surprised at how rigid the structure becomes when the knob is tightened firmly.

I have a mag base with three rods and two articulating couplers like this, but smaller, intended to hold a chip-guard. It's remarkably stiff despite the balls being very small. so I can imagine this would be good and solid. I'd be tempted to drill the holes undersize, then use a ball-nosed end mill the same size as the balls to get a matching curve on the holes. Over-engineer All The Things! I'll save this tip for a rainy day.

I re-hardened the balls by heating to cherry red and quenching in oil. No real need to champher the holes in the brackets as the sharp edge will lock onto the ball bearings, there's a lot of force applied to a small surface area. Trust me, if the knob is tightened firmly the arms won't move.

Thank you.

That would be a great idea!

Thank you. Glad you liked it.