According to Official Guinness Records,
The most melons chopped on the stomach on a bed of nails in one minute is 24, achieved by Ashrita Furman and Bipin Larkin (both USA), in New York, New York, USA, on 6 September 2016. The attempt was streamed on Facebook LIVE.
For a complete list of 2016 records, please visit 2016 Guinness Records in United States.