Multigroove drill bit with angled frontal ridges

A drill bit comprising a cylindrical shaft centered on an axis, said shaft having at least three external helical flutes respectively forming at least three lateral cutting edges and at least three angularly equispaced frontal ridges extending generally radially inward from said lateral cutting edges on a forward end face of said shaft, a first one of said ridges forming a first outer cutting edge and a first inner cutting edge along a common radius meeting at a first peak, a second one of said ridges forming a second outer cutting edge and a second inner cutting edge along a common radius meeting at a second peak, a third one of said ridges forming a third outer cutting edge and a third inner cutting edge along a common radius meeting at a third peak, all said outer cutting edges converging forwardly toward said axis, all said inner cutting edges converging rearwardly toward said axis, said first peak lying closer to said axis than said second peak, said second peak lying closer to said axis than said third peak, said first peak projecting axially forward beyond said second peak, said second peak projecting axially forward beyond said third peak, said first inner cutting edge including with said axis a smaller angle than said second cutting edge said second inner cutting edge including with said axis a smaller angle than said third inner cutting edge, said second inner cutting edge extending at least to said axis, said first and third inner cutting edges terminating short of said axis, said outer cutting edges all lying on a common imaginary conical surface centered on said axis, said inner cutting edges lying on imaginary coaxial conical surfaces intersecting one another in a common circle and being centered on a common axis.