This represents $235 a share, compared with Friday's closing price of $194.
Mr Buffett said he had "admired PCC's operation for a long time".
Berkshire Hathaway said it expected the deal, which is subject to PCC shareholder approval, to close during the first three months of next year.
"For good reasons, [PCC] is the supplier of choice for the world's aerospace industry, one of the largest sources of American exports," Mr Buffett said.
"Berkshire's board is proud that PCC will be joining [us]."
Mark Donegan, PCC chief executive, said the deal offered "compelling and immediate value for our shareholders".
PCC makes complex metal components for the aerospace, power and industrial sectors.
