Ezra Klein gives us a brief glimpse of history:

“There was one short-lived incident in the spring of 1979 that offers a glimpse of some of the problems and costs that might arise if the stalemate on Capitol Hill continues. Then, as now, Congress had been playing a game of chicken with the debt limit, raising it to $830 billion - compared with today’s $14.3 trillion - only after Treasury Secretary W. Michael Blumenthal warned that the country was hours away from the first default in its history. That last-minute approval, combined with a flood of investor demand for Treasury bills and a series of technical glitches in processing the backlog of paperwork, resulted in thousands of late payments to holders of Treasury bills that were maturing that April and May…’That the series of defaults resulted in a permanent increase in interest rates’ of more than half a percent, which over time translated into billions of dollars in increased interest payments on the nation’s debt.”