that "screw part" should have a keeper arrangement inside, like a shoulder on the head or a square plate with a tab, so yes you may be missing a part - that terminal commonly comes loose after 50 years of folks fiddling with it

Bill


Moved over to the Passing Lane

"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir
"When we tug a single thing on an old truck, we find it falls off" ~ me
Some TF series details & TF heater pics