I only checked the new sharpen skill on 1 weapon, so couldn't swear I didn't jot a number down wrong somewhere.

Level

Agility Requirement

Damage Bonus

1

6

16-27

2

7

24-37

3

8

32-46

4

9

40-56

5

10

47-64

6

12

55-74

7

13

61-81

8

14

69-91