Central cutting region of a drilling head assembly
View Patent ↗In one aspect of the invention, a drilling assembly comprises a head located on a rotational axis of the assembly and comprises at least one head element. At least one blade extends distally from the head. A plurality of blade degradation elements are rotationally supported on the blade. Each degradation element comprises an attack angle that affects the penetration rate of each degradation element and a laterally offset angle that primarily affects the rotational rate of each degradation element within their holders. The drilling assembly comprises a central cutting region. The blade degradation elements within the central cutting region form an attack angle of 15 to 20 degrees with the rotational axis of the drilling assembly.
1. A drilling assembly, comprising:
a head located on a rotational axis of the assembly;
at least one blade extending distally from the head;
a plurality of blade degradation elements being rotationally supported on the blade;
each degradation element comprising an attack angle formed between a central axis of the degradation element and the rotational axis of the assembly that affects the penetration rate of each degradation element and a laterally offset angle formed between the central axis of the degradation element and a line tangent to a helical cutting path of the degradation element that primarily affects the rotational rate of each degradation element within their holders fixed to the blade;
wherein the plurality of blade degradation elements comprise a wear resistant tip comprising a pointed sintered polycrystalline diamond compact supported on a cemented metal carbide support; and
a central cutting region of each blade;
wherein the attack angle of each blade degradation element within the central cutting region is between 15 and 20 degrees.
2. The assembly of claim 1 , wherein the central cutting region is defined within a 13 inch radius from the rotational axis of the drilling assembly.
3. The assembly of claim 1 , wherein the central cutting region is defined within a six inch radius from the rotational axis of the drilling assembly.
4. The assembly of claim 3 , wherein the attack angle is 16 to 18 degrees.
5. The assembly of claim 1 , wherein the blade comprises at least one degradation element.
6. The assembly of claim 1 , wherein the cemented metal carbide support is bonded to a cemented metal carbide bolster at a forward diameter, which comprises a cross sectional thickness less than or substantially equal to a largest diameter of the bolster.
7. The assembly of claim 1 , wherein the cemented metal carbide support is segmented.
8. The assembly of claim 7 , wherein at least one segment of the cemented metal carbide support is press fit into a cavity of a body of the degradation element.
9. The assembly of claim 7 , wherein the pointed diamond compact comprises a greater axial thickness than an immediately adjacent segment of the cemented metal carbide support.
10. The assembly of claim 1 , wherein the pointed diamond compact comprises a greater axial thickness than the cemented metal carbide support.
11. The assembly of claim 1 , wherein the pointed diamond compact comprises a curvature formed in a plane substantially parallel with a central axis of the tip.
12. The assembly of claim 11 , wherein the curvature is between 0.050 and 0.110 inch radius of curvature.
13. The assembly of claim 1 , wherein the assembly is an auger assembly.
14. A drilling assembly, comprising:
a head located on a rotational axis of the assembly;
at least one blade extending distally from the head;
a plurality of blade degradation elements being rotationally supported on the blade;
each degradation element comprising an attack angle formed between a central axis of the degradation element and the rotational axis of the assembly that affects the penetration rate of each degradation element;
wherein the plurality of blade degradation elements comprise a wear resistant tip comprising a pointed sintered polycrystalline diamond compact supported on a cemented metal carbide support; and
a central cutting region of each blade;
wherein the attack angle of each blade degradation element within the central cutting region is between 15 and 20 degrees.