By Anushree Mukherjee May 18 (Reuters) - U.S. drill bit manufacturers are shifting to steel-based products to cut costs as tungsten prices surge due to trade restrictions and tighter supplies. North American producers are expected to ‌ramp up drilling as disruptions to Middle Eastern oil supplies keep crude above $100 a barrel. But higher ‌drill bit and equipment costs are raising the price of new wells, potentially slowing output growth at a time when global markets are counting ​on more U.S. supply. ...