Ten minutes of brilliance kept Roger Federer on course for a final clash with Lleyton Hewitt at the Halle Open grasscourt event in Germany on Friday.
Sixteen-times Grand Slam champion Federer fired 12 aces to stay on top of the lively Kohlschreiber, winning in just over an hour to take his run at the pre-Wimbledon stop-off to 28 victories.
There was nothing to separate the pair until Federer, winner of the Halle title on his last five visits, stepped up a gear to close out the opening set and accelerate away.
"Ten strong minutes led to today's success. It was a bit of a bumpy start but then I found my rhythm," said Federer, who will be gunning for a seventh Wimbledon crown later this month.
The Swiss faces more German opposition in the semi-finals in the shape of Philipp Petzschner.
"That is not going to be easy. Philipp has played really well here," said Federer.
Australian Hewitt, the 2002 Wimbledon champion, will also face a German opponent in the semis after Benjamin Becker beat compatriot Mischa Zverev 7-6, 6-0.
