That's an excellent question, Wayne.  For years, I've followed these kinds of tests closely for obvious reasons, and a lot of them are subjective, with little in the way of scientifically designed boundary conditions.  I have them back to over ten years ago, and probably further, mostly in the vehicle maintenance and home shop machining communities for obvious reasons.  Everyone swears by this solution or that, but the sample set that any one of us radio guys personally has is painfully low - how many of us do it on a regular basis with dozens of samples?  And the real problem is that the size of the test threads in these tests is almost always significantly larger than the relatively small screws (like knob setscrews) that we have to address most frequently.  Life ain't always linear. 

There is a later method that I've found useful, but it too involves some limitations based on surrounding knobs/handles/etc., and that's an induction heater.  The most difficult setscrews I have ever encountered are on the glued-in screws in BC-191/375 transmitter dials, and 10-15 seconds of heating works wonders without harming the black bakelite knobs or paint at all.  If you can fit the coil around the knob, it has always provided the cure - at least for me.  This has been verified by the home shop machinist and vehicle communities as well, but the difficulty is always the geometry of the frozen screw/bolt with respect to surrounding structures.  The professional models are a bit pricey and require a bevy of different coil shapes and sizes in an attempt to cover the most situations.  I picked up one for a few bucks on Amazon (search "low voltage induction heaters", if interested)  but the quality of these Chinese products runs all over the place, and you do need to wind more than one coil set for different size radio knobs.  The good news is that these cheap drivers generally work on 12-14vdc or 24-28vdc, voltages which may sound familiar to most of you.

 
As a result of its limitations, I would never call this solution the answer to the "Ultimate Question of Life, the Universe, and Everything".  That allegedly remains "42" according to The Hitchhikers Guide to the Galaxy.  YMMV.  😁

Just another data point for consideration...as if we needed more.

     73,
 - Mike  KC4TOS