Formation-engaging structures having retention features, earth-boring tools including such structures, and related methods

1. An earth-boring tool, comprising:

a body with a receptacle for accepting a formation-engaging structure;

a retainer bore accepting a retaining element, the retainer bore extending along a generally linear path through the body of the earth-boring tool and contiguous with a retainer recess intersecting a sidewall of the receptacle; and

a formation-engaging structure disposed within the receptacle of the body of the earth-boring tool, the formation-engaging structure comprising:

a formation-engaging portion disposed at a distal end;

a side surface between a proximal end and the distal end along a central axis of the formation-engaging structure; and

at least one recess in the side surface, wherein a portion of the retaining element is adjacent a surface of the formation-engaging structure protruding into the at least one recess and adjacent the retainer recess, and

wherein the at least one recess in the side surface of the formation-engaging structure is located and configured such that rotation of the formation-engaging structure within the receptacle about a central longitudinal axis of the formation-engaging structure causes the at least one recess to bear against the retaining element and the formation-engaging structure to move in a direction along the central longitudinal axis of the formation-engaging structure relative to the receptacle of the body.

2. The earth-boring tool of claim 1 , wherein the retaining element is an elongated pin.

3. The earth-boring tool of claim 2 , wherein the retaining element comprises a resilient material coiled about a longitudinal axis.

4. The earth-boring tool of claim 1 , wherein the at least one recess in the side surface of the formation-engaging structure comprises an arcuate transverse cross-sectional shape.

5. The earth-boring tool of claim 1 , wherein the formation-engaging structure further comprises at least one feature configured to interface with a tool adapted to apply torque, the at least one feature disposed in at least one of the side surface and the formation-engaging portion.

6. The earth-boring tool of claim 1 , wherein the side surface of the formation-engaging structure is substantially cylindrical, and wherein the at least one recess in the side surface comprises:

a generally linear recess in the side surface extending along an axis oriented at a non-parallel angle relative to the central axis of the formation-engaging structure; and

a generally helical recess in the side surface, the generally helical recess intersecting the generally linear recess.

7. The earth-boring tool of claim 6 , wherein the non-parallel angle is an angle of between about forty-five degrees (45°) and about one hundred thirty-five degrees (135°).

8. The earth-boring tool of claim 7 , wherein the non-parallel angle is an angle of about ninety degrees (90°).

9. The earth-boring tool of claim 6 , wherein the generally helical recess extends around about one hundred eighty degrees (180°) or less of a circumference of the formation-engaging structure.

10. The earth-boring tool of claim 9 , wherein the generally helical recess extends around about ninety degrees (90°) or less of the circumference of the formation-engaging structure.

11. The earth-boring tool of claim 6 , wherein the generally linear recess intersects the generally helical recess at a distal end of the generally helical recess.

12. The earth-boring tool of claim 6 , wherein the generally linear recess intersects the generally helical recess at a proximal end of the generally helical recess.

13. The earth-boring tool of claim 6 , wherein the generally helical recess comprises an arcuate transverse cross-sectional shape.

14. The earth-boring tool of claim 1 , wherein the earth-boring tool is a fixed-cutter drill bit.

15. An earth-boring tool, comprising:

a body with a receptacle for accepting a formation-engaging structure;

a retainer bore accepting a retaining element, the retainer bore extending along a generally linear path through the body of the earth-boring tool and contiguous with a retainer recess intersecting a sidewall of the receptacle; and

a formation-engaging structure disposed within the receptacle of the body of the earth-boring tool, the formation-engaging structure comprising:

a formation-engaging portion at a distal end;

a generally cylindrical side surface between a proximal end and the distal end along a central axis of the formation-engaging structure;

a generally linear recess in the generally cylindrical side surface extending along an axis oriented with a non-parallel angle relative to the central axis of the formation-engaging structure; and

a generally helical recess in the generally cylindrical side surface, the generally helical recess intersecting the generally linear recess, wherein a portion of the retaining element is adjacent a surface of the formation-engaging structure protruding into the generally helical recess, and

wherein the generally linear recess and the generally helical recess are located and configured such that rotation of the formation-engaging structure within the receptacle of the body about a central longitudinal axis of the formation-engaging structure causes one or more of the generally linear recess and the generally helical recess to bear against the retaining element and the formation-engaging structure to move in a direction along the central longitudinal axis of the formation-engaging structure relative to the receptacle of the body.

16. The earth-boring tool of claim 15 , wherein the generally linear recess comprises a cross-sectional shape with a constant radius of curvature.

17. The earth-boring tool of claim 16 , wherein the generally helical recess comprises a cross-sectional shape with a constant radius of curvature greater than the radius of curvature of the cross-sectional shape of the generally linear recess.

18. A method of forming an earth-boring tool, comprising:

providing a body with a receptacle for accepting a formation-engaging structure and a retainer bore for accepting a retaining element, the retainer bore extending through the body along a substantially linear path and comprising a retainer recess intersecting a sidewall of the receptacle;

inserting a proximal end of a formation-engaging structure into the receptacle with a distal end comprising a formation-engaging portion protruding from the body; and

inserting a retaining element into the retainer bore and the retainer recess adjacent a recess in a side surface of the formation-engaging structure,

wherein the recess in the side surface of the formation-engaging structure is located and configured such that rotation of the formation-engaging structure within the receptacle of the body about a central longitudinal axis of the formation-engaging structure causes the recess in the side surface of the formation-engaging structure to bear against the retaining element and the formation-engaging structure to move in a direction along the central longitudinal axis of the formation-engaging structure relative to the receptacle of the body.

19. The method of claim 18 , wherein inserting a proximal end of a formation-engaging structure into the receptacle comprises inserting a proximal end of a formation-engaging structure having a generally helical recess in the side surface and a generally linear recess in the side surface in intersecting relationship and inserting the retaining element adjacent a portion of the generally linear recess.

20. The method of claim 19 , wherein inserting a proximal end of a formation-engaging structure having a generally helical recess in the side surface and a generally linear recess in the side surface in intersecting relationship comprises inserting a proximal end of a formation-engaging structure wherein at least one of the generally helical recess and the generally linear recess have a substantially arcuate transverse cross-sectional shape.