A serial sex offender — whose attacks on three Bronx prostitutes were so violent, he was once eyed in the hooker slayings on Long Island — was sentenced yesterday to 60 years in prison for three knifepoint attacks.

Bronx jurors had taken less than half an hour to convict James Schlau, 47, on charges that he used a homemade razor-knife three times to force victims to perform oral sex on April 18, June 16 and June 28, 2010.

All three victims said Schlau tried to rape them.

“One of the victims said he threatened to cut her genitalia, another said he threatened to cut her throat,” prosecutor Astrid Borgstedt reminded the judge before sentencing.