Tapio Pulkkanen produced another faultless round, which began with six straight birdies, to claim the lead of the Joburg Open as Shubhankar Sharma moved up to second with a sublime 61 on Friday.
Pulkkanen, who earned his European Tour card by topping the Challenge Tour's order of merit in 2017, completed an eight-under 64 on the Firethorn course, having been six under around the Bushwillow course 24 hours earlier.
The Finn's stunning start was followed by further gains at 11 and 12, enough to earn a one-stroke lead at 14 under.
"Six birdies in a row to start with was an awesome start," said Pulkkanen. "I had some tough times midway [through the round] but I managed to make good pars and then I made a couple of birdies on the back nine."
Shubhankar is Pulkkanen's nearest rival, having surged into contention courtesy of a stunning round on the Bushwillow course that featured 10 birdies and eight pars.
Charlie Ford looked as though he would challenge both men when he went eagle-birdie-eagle from the 12th, but bogeys at 16 and 17 set him back before signing for an eight-under 64 on the Firethorn course.
Erik van Rooyen and Pulkkanen's compatriot Mikko Korhonen are tied for third, two shots off the lead on 12 under having recorded respective rounds of 67 and 65.
Overnight leader Keenan Davidse slumped down the field with a dismal 74 on the Firethorn course. Having led by one, Davidse is now eight off the pace.