Scantling will be sentenced in October. He could spend up to 25 years in prison.
Police say he attacked Dewayne Taylor on the subway back in September, 2008.
The brutal attack was caught on surveillance video.
RELATED VIDEO: Hammer attacked caught on tape (WARNING: Graphic content)
Taylor appeared to be attacked for no reason.
Scantling was arrested five days later at a mental health facility.
Get Action News on your website
Follow Action News on Facebook
Click here to get the latest Philadelphia news and headlines from across the Delaware and Lehigh valleys.