What determines the discard criteria of a Tophammer drill bit is typically that it reaches the minimum allowable diameter. During the lifetime of the bit, it needs to be able to effectively evacuate the crushed rock cuttings to be able to keep drilling. To do this the milled cutting grooves in the front and side of the bit head need to be large enough to flow said cuttings. Thus, a good bit need to have cutting grooves deep enough even at its discard diameter so that it can keep drilling efficiently all the way until discard. Most traditional bits does not have this feature as it adds machining cost. Thus the traditional bits often lose their ability to drill efficiently after very limited wear.
Another designed advantage of the deeper cutting grooves is that it minimizes the amount of steel needed to be removed during bit regrinding.
The flushing hole configuration of the Powerbit Underground is totally new on the market and have been developed through extensive fluid flow simulations in the Epiroc proprietary developed CFD models followed by extensive lab and field testing. The flushing configuration with three front flushing holes and three correctly placed side flushing holes allows the bit to keep drilling even through conditions which blocks the front flushing holes. The flushing pattern is optimal no matter if all six holes are flowing or if only the three side flushing holes are flowing.
This effectively crushes the age old compromise of side flushing holes which typically counteracts the front flushing holes as well as trapping rock cuttings increasing the body wear in the vincinity of the traditionally placed side flushing hole.
The design instead utilizes Epiroc state of the art machining capabilities to be able to deliver a drill bit that drills efficiently all the way to discard as it really is the Total Cost of the Operation that gives the impact on the bottom line rather than the unit cost of the drill bits.
Read more about Powerbit Underground here!