CLARK, N.J. — WHEN Hyatt Clark Industries makes its last roller bearing here in August, it will fade into history as one of the nation's most closely-watched - and perhaps most disheartening - industrial experiments of the 1980's.

The company, now in bankruptcy proceedings, is one of the hundreds of heavy manufucturing concerns that have succumbed to a familiar litany of problems: foreign competition, changing technology, and friction between labor and management.

But the difference is that Hyatt Clark, which has for more than 50 years made bearings for the General Motors Corporation, has been owned since 1981 by its employees. It was supposed to be a model of what employees could do when they are given free rein and a vested interest in their company, a proof that employee ownership, if not a panacea for the ills of smokestack America, was the best way to improve productivity.

Instead, Hyatt Clark has emerged as a case study in how the best laid plans can go awry.