2821: The mechanism is a differential-screw, so there's a HUGE
mechanical advantage (and the wide wings make it easy to really
crank down). It's a cable/wire clamp, or possibly a crimp tool (though
it's hard to visualize what gets crimped).
2822: an electrical commutator, probably for the purpose of rectifying AC to DC.
The shaft would be driven by an AC synchronous motor, the brushes would
connect AC only during the positive half-cycle.
2823: Some kind of scraper to clean the inside of a hole?
2824:The long handle suggests a dirty job; chimney cleaning scrubber?
2825: A powered nutcracker, for use on coconuts?