This is almost certainly Russian SF: "Crabs walk on the Island" by Anatoly Dneprov.
The robots are crabs that rapidly evolve, as part of an experiment by the Navy. The crab robots are constantly seeking to build better robots, and compete for the (purposefully limited) minerals on the island. When the minerals start running low, there is open warfare between competing crabs which evolve differently: there are extremely fast and small crabs which run on solar power, and hulking slow giants with batteries. The scene you remember is when the crabs kill the chief engineer, one of the two guys on the island, in order to extract his stainless steel tooth.
I reached up and got on its back. For an instant Cookling's distorted
face came level with mine. "His teeth!" suddenly crossed my mind. "His
stainless steel false teeth!"
I struck the parabolic mirror, shining in the sunlight, as hard as I
could with my fist.
This is a fun story. Not sure where it can be obtained legally, but it's easy to find an English translation if you google it.