Sandelin, the first-round leader, shot a 4-under 68 to earn a deadlock with his 1999 Ryder Cup teammate at 10-under-par 134. The duo leads by three strokes over a group of five players tied for third place.
Among those at 7-under-par 137 is Paul Lawrie, also a 1999 European Ryder Cupper, who shot a 69 in his second round. Bradley Dredge (65), Nicolas Colsaerts (67), Garry Houston (69) and Damien McGrane (69) are also at minus- 7. Dredge was the 2003 champion here.
Van de Velde began the day in a tie for seventh place at 3 under, but the Frenchman made quick strides by playing the front nine at minus-four on Friday.
He played the first two par-5s-- Nos. 3 and 7 -- a combined 3 under, picking up an eagle at the 538-yard seventh. A birdie at the ninth put him at minus-7.
Van de Velde added three birdies on the back nine. Continuing his attack on the par-5s, two of his final three birdies came at the 572-yard 11th and the 556-yard 16th.
The last time Van de Velde found himself at the top of the leaderboard after two rounds was the weekend of his collapse at the 1999 British Open. He played on invitations only last season, but recovered his tour card with a second- place finish at the Open de France.
'The way I see it is that I have been given a second chance to have a second career,' Van de Velde said. 'There are going to be some good times and horrific times, that I know, and I have experienced that in the past. But this is a different story.'
Sandelin held the overnight lead at minus-six, but dropped a stroke at the par-3 fourth on Friday. He got that shot back, though, with a birdie at the next and was 8 under around the turn after additional birdies at seven and eight.
After two straight pars, Sandelin reached 9 under with a birdie at the par-5 11th. He added a fifth birdie at the par-3 17th to join Van de Velde in the lead.
Sandelin is in a similar position as Van de Velde, having needed a 10th place finish at Q-school last year to retain his tour card.
'I am really looking forward to tomorrow,' said Sandelin. 'It feels good just now...If I can keep the game plan to hit the greens and not try to be too offensive when the flags are too far back on the greens, then I will be all right.'
Pedro Linhart, the 1999 champion, shot a 5-under 67 on Friday to reach minus-6. He shares eighth place with cousins Sam Walker (69) and Tom Whitehouse (65).
The cut line fell at even-par, with 67 players moving on to the weekend.