Matrix hardness is an important characteristic of diamond bit. It should be suitable for hardness (drillability) and abrasiveness of rock to be penetrated. Matrix hardness has direct influence on technical and economical indexes of drilling and choice of drilling parameters. Experimental research shows, that matrix hardness difference is big and not fairly well-distributed. The main reason of the big hardness difference may be low pressure (5 MPa) while sintering process of hot pressing. Diamond bit, drilling parameters and operation technology are all important. Probably low technical and economical results of diamond drilling are not connected with the bit, but with the drilling parameters and operation technology. Transition from drilling with experience to drilling with science is advocated.