not turn a hair—
1. not show any sign of being troubled:
- Catherine adapted to the wilds of Africa amazingly well—she did not turn a hair at having lions walking past the back door.
2. be not affected by exertion:
- Hot! He had not turned a hair till we came to Walcot Church; …that horse cannot go less than ten miles an hour.
turn of a hair—a close chance; a narrow escape from a dangerous situation:
- It was the turn of a hair that they hadn’t buried him alive.