The 25-year-old from Walker Cup player from Durham, a European Tour rookie, improved 15 strokes on his opening 78 and moved up from 129th to joint 20th on three under.
Dinwiddie, in the last group of the day, finished with five straight birdies not just to knock two shots off the record for the lengthened lay-out, but to equal the old mark of Nick Job and Wayne Riley.
People may remember Ernie Els scoring 60 around the course but that was in the World Match Play Championship and not every putt was holed, so therefore did not constitute a course record.
"To hold the Wentworth course record is something special," he said. "To putt as well as I did is just tremendous.
"I was hoping maybe for five or six under and make the cut. That was fantastic. I lost track of it at one point, but just kept hitting good shots."