Cutting elements and drill bits incorporating the same

1. An ultra-hard cutting element for use in a drill bit, comprising:

a base portion defining a longitudinal axis;

an extension portion on an end of the base portion, wherein at least a portion of an outer surface of the extension portion includes an ultra-hard abrasive material selected from the group consisting of polycrystalline diamond or polycrystalline cubic boron nitride; and

a lip on the outer surface of the extension portion, the lip having a length between a first end and a second end, wherein the extension portion outer surface includes a first outer surface portion being spherical or elliptical and extending from the base portion to the lip, and a second outer surface portion being spherical or elliptical and extending from the base portion to the lip, wherein the lip is between the first and second outer surface portions, and wherein the first outer surface portion extends to a maximum first height as measured axially from the base portion, and wherein the second outer surface portion extends to a maximum second height as measured axially from the base portion, wherein the maximum first height is greater than the maximum second height.

2. The ultra-hard cutting element of claim 1 , wherein at least a portion of the ultra-hard abrasive material has a hardness of at least approximately 4000 kg/mm 2 .

3. The ultra-hard cutting element of claim 1 , wherein the first outer surface portion is spherical having a first radius of curvature and the second outer surface portion is spherical having a second radius of curvature less than the first radius of curvature.

4. The ultra-hard cutting element of claim 3 , wherein the lip extends beyond the first spherical portion.

5. The ultra-hard cutting element of claim 3 , wherein an outer end of the lip is flush with the first spherical portion.

6. The ultra-hard cutting element of claim 3 , wherein the lip comprises a cutting face extending between the first spherical portion and the second spherical portion.

7. The ultra-hard cutting element of claim 6 , wherein the cutting face is substantially perpendicular to the second spherical portion.

8. The ultra-hard cutting element of claim 6 , wherein the cutting face is canted at an angle from approximately 15 degrees to approximately 60 degrees relative to the second spherical portion.

9. The ultra-hard cutting element of claim 1 , wherein the lip extends diametrically across the outer surface.

10. The ultra-hard cutting element of claim 1 , wherein the lip is offset from the longitudinal axis.

11. The ultra-hard cutting element of claim 1 , wherein a height of the lip tapers between a higher end proximate the longitudinal axis and lower ends proximate an interface edge between the outer surface and a sidewall of the base portion.

12. The ultra-hard cutting element of claim 1 , wherein a height of the lip is substantially constant along the length of the lip.

13. The ultra-hard cutting element of claim 1 , wherein the base portion is cylindrical.

14. The ultra-hard cutting element of claim 1 , wherein an outer surface of the lip comprises the ultra-hard abrasive material extending from the first outer surface portion to the second outer surface portion.

15. The ultra-hard cutting element of claim 1 , wherein the element has a lip height defined as the height of the lip relative to the second height, and a ratio of the lip height to the diameter of the base portion is from 0.01 to 0.4.

16. A drill bit, comprising:

a shank;

a bit body on one end of the shank, the bit body defining a plurality of cutter pockets; and

a plurality of ultra-hard cutting elements at least partially received in the plurality of cutter pockets, wherein at least one of the plurality of ultra-hard cutting elements comprises:

a base portion defining a longitudinal axis;

an extension portion on an end of the base portion, wherein at least a portion of an outer surface of the extension portion includes an ultra-hard abrasive material selected from the group consisting of polycrystalline diamond or polycrystalline cubic boron nitride; and

a lip on the outer surface of the extension portion, the lip having a length between a first end and a second end, wherein the extension portion outer surface includes a first outer surface portion being spherical or elliptical and extending from the base portion to the lip, and a second outer surface portion being spherical or elliptical surface and extending from the base portion to the lip, wherein the lip is between the first and second outer surface portions, and wherein the first outer surface portion extends to a maximum first height as measured axially from the base portion, and wherein the second outer surface portion extends to a maximum second height as measured axially from the base portion, wherein the maximum first height is greater than the maximum second height.

17. The drill bit of claim 16 , wherein the first outer surface portion is spherical having a first radius of curvature and the second outer surface portion is spherical having a second radius of curvature less than the first radius of curvature.

18. The drill bit of claim 16 , wherein the lip extends diametrically across the outer surface.

19. The drill bit of claim 16 , wherein the ultra-hard cutting elements are oriented on the bit body such that the lip extend radially toward a longitudinal axis of the shank.

20. The drill bit of claim 16 , wherein an outer surface of the lip comprises the ultra-hard abrasive material extending from the first outer surface portion to the second outer surface portion.