Earth-boring tools including formation-engaging structures having retention features and related methods

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

providing a tool 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 tool body along a substantially linear path and comprising a retainer recess intersecting a sidewall of the receptacle;

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

inserting the formation-engaging structure in the receptacle; and

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

2. The method of claim 1 , wherein forming the helical recess and the linear recess in intersecting relationship comprises forming the helical recess to intersect the linear recess at a proximal end of the helical recess.

3. The method of claim 1 , wherein forming the helical recess and the linear recess in intersecting relationship comprises forming the linear recess to intersect the helical recess at a distal end of the helical recess.

4. The method of claim 1 , wherein forming the helical recess and the linear recess in intersecting relationship comprises forming the helical recess at an oblique angle with a plane oriented normal to the central axis of the formation engaging structure.

5. The method of claim 1 , wherein forming the helical recess and the linear recess comprises forming the helical recess and the linear recess to have a substantially arcuate cross-sectional shape.

6. The method of claim 5 , wherein forming the helical recess and the linear recess to have a substantially arcuate cross-sectional shape comprises forming the linear recess to comprise a first radius of curvature less than a second radius of curvature of the helical recess.

7. The method of claim 1 , further comprising forming at least one planar surface in the side surface configured to interface with a tool adapted to apply torque to the formation-engaging structure.

8. An earth-boring tool, comprising:

a tool body comprising a receptacle and a retainer bore, the retainer bore extending along a generally linear path through the tool body and contiguous with a retainer recess intersecting a sidewall of the receptacle;

a formation-engaging structure disposed in the receptacle, the formation-engaging structure comprising:

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

a recess in the side surface comprising:

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

a generally helical portion in intersecting relation with the generally linear portion;

a retaining element disposed in the retainer bore; and

wherein a portion of the retaining element is adjacent a surface of the formation-engaging structure protruding into the recess and adjacent the retainer recess.

9. The earth-boring tool of claim 8 , 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 about the central axis of the formation-engaging structure causes the recess to bear against the retaining element and the formation-engaging structure to move in a direction along the central axis of the formation-engaging structure relative to the receptacle of the body.

10. The earth-boring tool of claim 8 , wherein the generally helical portion of the recess forms an oblique angle with a plane oriented normal to the central axis of the formation engaging structure.

11. The earth-boring tool of claim 10 , wherein the oblique angle is less than 90 degrees.

12. The earth-boring tool of claim 11 , wherein the oblique angle is less than 45 degrees.

13. The earth-boring tool of claim 10 , wherein the oblique angle varies along a portion of the generally helical portion of the recess.

14. The earth-boring tool of claim 8 , wherein the recess extends around about 180 degrees or less of a periphery of the side surface.

15. The earth-boring tool of claim 14 , wherein the recess extends around about 90 degrees or less of the periphery of the side surface.

16. The earth-boring tool of claim 8 , wherein the formation-engaging structure comprises a wear-resistant material.

17. The earth-boring tool of claim 8 , wherein mechanical interference between the retaining element and the formation-engaging structure retains the formation-engaging structure within the receptacle.

18. A method of removing a formation-engaging structure from a receptacle in a body of an earth-boring tool, comprising:

removing a retaining element from a linear recess in a side surface of the formation-engaging structure;

applying a rotational force to the formation-engaging structure about a central axis thereof; and

bearing a surface of the formation-engaging structure within a helical recess in the side surface of the formation-engaging structure against the retaining element forcing the formation-engaging structure in a direction parallel to the central axis thereof.

19. The method of claim 18 , further comprising:

removing the retaining element from the helical recess in the side surface of the formation-engaging structure; and

removing the formation-engaging structure from the receptacle.

20. The method of claim 18 , wherein removing the retaining element from the linear recess comprises driving the retaining element out of the linear recess using at least one of a pin punch or hammer.