You should be able to easily find 1/4" steel cable with a rating of
over 3 tons so annealing shouldn't become a major problem. However: Is
this an application where someone could be injured by the end pulling
out? If so I might suggest assembling the cable end into a wedge shape
by brazing, with a central tiny wedge inside (or by bending the strands
inwardly over themselfs) and quenching while it's still hot followed by
a lighter heat to finish temper (a lot of technique needed here). Then
match the cone shape by milling/filing out the ball and finish by
running the cable through the ball and lightly soldering.
Not too stupid sounding, I hope.
Dennis in nca