| 摘要 |
A center vacuum rotary drill bit including a drill bit body having a top working surface. Formed within the top working surface is a slot having disposed therein an insert positioned within a shim within the slot. The insert includes a pair of oppositely facing generally parallel side surfaces, a pair of oppositely facing generally parallel end surfaces extending between and interconnecting said side surfaces, a pair of oppositely inclined top surfaces extending between and interconnecting said side and end pairs of surfaces, and a bottom surface having a concave depression formed therein. The bottom surface extends transversely to and interconnects the side and end pairs of surfaces. A support bar including a convex top surface is disposed within the slot between the insert bottom surface and the slot such that the convex top surface supports the concave depression of the insert. In a preferred embodiment, the modulus of elasticity of the support bar is greater than the modulus of elasticity of the shim. |
