He finished 36 holes at 13-under-par 131 and is three shots clear at Pete Dye Golf Club.
Edward Loar fired an eight-under 64 on Friday and is alone in second place at minus-10.
Matthew Jones shot a 5-under 67 and is tied for third place with David Hear, who carded a 2-under 70 in round two. The pair is knotted at 9-under-par 135.
McLachlin started on the back nine Friday and parred his first four holes. He broke into red figures on his round with a seven-foot birdie putt at the par-5 14th, then made it two in a row with a 10-footer at the 15th.
McLachlin made his first bogey of the tournament at the par-three 16th, thanks to a three-putt. He answered with an eight-foot birdie putt at the 17th, but dropped another shot to par after a bad drive at 18.
At the par-four third, McLachlin chipped his second from shy of the green to 10 feet and made the putt for birdie. He moved clear of the field with a two- putt birdie at the par-five sixth and a eight-foot birdie at six to reach minus-13.
McLachlin parred his last two and is halfway home to win No. 1 on the Nationwide Tour.
'I think I had some early-round jitters on those first few holes,' admitted McLachlin. 'I did real well to make four pars. I switched the green light on at the par five (14). It was time to get it going.'
Temperatures soared on Friday at the Pete Dye Golf Club and McLachlin's caddie fell prey.
'My caddie had to be taken off the course on No. 5,' said McLachlin. 'The paramedics came and got him off the course. He was cramping up.'
Scott Parel shot a one-under 71 and is alone in fifth place at minus-eight.
Ian Leggatt (70), Todd Fischer (68), Justin Hicks (66), Scott Dunlap (66), Todd Demsey (69), Brad Ott (69) and Kevin Gessino-Kraft (70) are knotted in sixth at seven-under-par 137.
The 36-hole cut fell at one-under-par 143 and Nick Flanagan, who earned a promotion to the PGA Tour with his third win last week, and the tour's leading money winner Roland Thatcher missed the cut