Lucas Herbert has kept his foot on the pedal to extend his lead at the halfway mark of the ISPS HANDA Australian Open at Kingston Heath but remains very wary of the challenge coming from his Ripper GC captain Cam Smith.

Thanks to a 6-under-par 66 which followed his first day 63 at Victoria Golf Club, Herbert sits at 14-under with a four-shot lead over American Ryggs Johnston (65-68)

A healthy group of six players are tied third at 9-under, headlined by last week's BMW Australian PGA Champion Elvis Smylie, who produced one of the shots of the day to grab a final birdie on 18 to close out an 8-under round of 64.

Tied with Smylie are a string of internationals, with Americans Harry Higgs (68) and Jordan Gumberg (69) continuing their love of the Sandbelt, while DP World Tour players Oliver Lindell (69), Lukas Nemecz (66) and Matthew Southgate (68) well placed to try chase down Herbert.

Cam Smith is T16 at 6-under after a 72 today where he shot 5-under on the front nine before slipping up with three bogeys and a double-bogey on his back nine.

Playing in the afternoon sunshine at Kingston Heath today though, the attention was largely on three men – Herbert, Smith, and Smylie, as the wind whipped through Melbourne's bayside region.

Not wanting to relinquish his overnight lead, Herbert got about scoring fast and early. Eagle, birdie, birdie had the NSW Open champion reach 12-under for the championship before some of the afternoon groups had even started to walk to the first tee.

The scoring slowed from the fourth though, and 12-under is where he would remain as he made the turn.

"I thought it was funny. I played pretty good yesterday, just didn't really putt that well and then felt like I putted really well today, scrambled really well and the rest of the game was sort of off," Herbert said.

"So it was kind of funny. It was like two days of polar opposites to have good scores."

In the group ahead Herbert, two men were making a charge in Smith and Smylie.

Like Smith, Smylie turned in 5-under, but unlike the 2022 Open champion, he was able to keep the foot on the pedal to get himself back in the Open after a modest 1-under 70 at Victoria on day one.

"It felt like the whole group did a really good job at feeding off each other, momentum wise," said Smylie.

"We holed a lot of putts on the front nine and the course was playing quite scoreable, so I felt like we did a really good job at capitalising on some of those."

A Herbert bogey on 10, his first of the week, looked as if he may be heading down the Smith route, however the Bendigo boy shook it off quickly with a string of three birdies 13 through 15.

The pin on The Heath's famous 15th was treacherously tucked in the front funnel, but as Herbert's tee shot danced around the pin and he tapped in for birdie, it was clear he is a class above this week so far.

"Some tricky tee shots on that back nine and just to stay really positive with the swings I was making, I'm really proud of those last three or four holes there," Herbert said.

"16 tee shot, not an easy one. The 18 tee shot not an easy one under the circumstances and I thought I handed them really, really well."

Two weeks ago it was Herbert chasing Smith to claim the NSW Open at Murray Downs, and while he will start Saturday's round 8-shots clear of the 2022 Open champion, Herbert is not counting him out. After all, he did it to Rory at St Andrews.

"I'm expecting him to make a run," Herbert said. "I can't shoot 72-72 this weekend and expect to win this golf tournament.

"There's a lot of work still to be done, and I'm expecting these guys behind me to make a charge."