An impregnated bit is not a consumable you buy by diameter alone. The matrix must wear at the same rate as the diamonds expose, and that rate is set by rock hardness and abrasiveness together.
For hard, competent rock such as granite or quartzite, use a hard matrix (higher WC content) with a shallow crown. A soft matrix in hard rock wears away before the diamonds do, and you lose the bit before it has cut anything.
For abrasive, broken formations such as schist or saprolite, use a softer matrix with deeper waterways. The rock abrades the matrix quickly; a hard matrix glazes and stops cutting.
Waterway design matters more than most buyers expect. In swelling clay, wide waterways block; in hard rock, narrow waterways create the face velocity needed to cool the crown.
If you send us a core photo with depth, rod size and rotation speed, we will recommend a matrix step and crown profile. It is faster than trial and error at 400 m.
