Nice, knowledgeable work.
I own two commercial versions of these pliers. They are more delicate than one suspects.
Not for bending small parts - just for handling.
The alignment of the 3 bores and and their play and the play in the slot are very important for the parallelism.
I deem the strength of the 16 gauge (1.6mm) mild steel too low for an unsuspecting man's grip.
Option: a heat treated carbon steel of greater thickness (2mm).